The UniversÍty of Manitoba
BIONOMICS 0F THE SUNFLOWER BEETLE, Zygognamma exclamationis (F. ) (COLfOptsRA:CHRYSOMELIDAE), AND ITS
PAMSITES IN MANTTOBA
by
Gannet Bruce Neill
A Thesis
Submitted to the Facutty of Gnaduate Studies
In Par"tiat Fulfillment of the Requinements for the
Degnee of Docton of Philosophy
Depantment of Entomology
Winnipeg, ManÍtoba
T982 BIONOMICS OF TIIE SUNFLOI'IER BEETLE, ZYGOGRAI"ÍMA
EXCLA},IATIONIS (F. ) (COLEOPTERA:CHRYSOMELIADAE) , AND ITS
PARASITES IN MANITOBA
BY
GARNET BRUCE NEILL
A thesis submitted to the Faculty of Graduate Studies of the University of Manitoba irr partial fulfillment of the requirements of the degree of
DOCTOR OF PHILOSOPHY o 1982
Permissiort has been granted to the LIBRARY OF THE UNIVER- SITY OF MANITOBA to lend or sell copies of this thesis, to the NATIONAL LIBRARY OF CANADA to microfilm this thesis a¡ld to lend or sell copies of the filnr, and UNIVERSITY MICROFILMS to publish an abstract of this thesis.
The author reserves other publication rights, and neither the thesis nor extensivc extracts from it may be prirrted or other- wise reproduced without the author's written permission. 11
ABSTRACT
The sunflowen beetle, Zygognarnrna exclamationis (F.), has one genenation per yean in Manitoba. The beetle ovenwintens as a sexually immatr::re adul-t in soil, usually at a depth of 15 cm or less, in fiel-ds in which it completed lanval development. Mating and egg-laying do not take plaee príon to hibennation.
The mean date of finst emengence of beetles, ovell a foun-yean pe::iod, was May 20, the nange being May 11 to 27. In one year, ovenwintening beetles emerged oven a peniod of 24 days with peak emengence on day 13. A method fon pr.edíetíng the time of emengence of ovenwintering beetles was developed using a system of thenmat unit (fU) accumul-ations based on soil- temperature necordings fuom a depth of 5 cm.
Males emenged one to foun days before females duning the initial emergence peniod, but no diffenences wene noted thereaften. Mal-es and fenales wene distinguishable by the shape of the fifth abdominal ster"nite. Sexual matur"ation was initiated eithen befone o:r sho::t1y afte:: emergence fuom hibernation. Posthibennation sexual development was napid, mating being noted within two days of finst emelrgence and egg- laying within one week of eme::gence. BehavÍoun duning cor:r'tship was simple and basic, and both males and females mated frequentty thnoughout the oviposition peniod.
Orce oviposition was initiated, females laid eggs almost every ,, day during the oviposition peniod. Eggs wene laid on the leaves and stem of the host plant and wene usually found singly on ín ir"negular iii groups. FemaLes neared in the labor"atony at 25oC laid an avenage of
30.7 eggs per" day drring an ovíposition pe:riod of 60.7 days. Egg pnoduction pen female avenaged 11965 with a nange of 260 to 31587. In field tnials, the average daily egg pnoduction was 15.2, oven a mean oviposition peniod of 47.1 days. The mean egg pnoduction in two field tnials was 719 with a nange of !32 to 1,554. Eggs wene pnesent ín commencial sunfl-owe:: fields fon six to seven weeks. Most beetles died shortly aften oviposition ceased.
The íncubation peniod of the eggsr which are clream to yellow and measu::e 1.33 by 0.61 mm, vras affected by tempenature above 9.goC, the lowen th¡eshold tempenatune for development (ToLO); the estinated the::nal r:nit nequirement fon incubation was 83.
Lar"vae passed thnough four instans distinguishable by width of the head capsule. As with incr:batíon, tempenatuï,e sÍgníficantly affected the dur"ation of the lanval stage. The estimated ToLO fon the finst- to fou::th-instans was 8.1, B.9o 7.5 and 3.8oC, nespectively, and estimated TU nequinement at the corresponding ToLOts was 76, 50, 63 and
83, respectively. A ToLO of 8.4oC râras necortrnended for pnedictíng lanval development in the field.
Over. a thnee-yean peniod, the mean date of first and last appearance of larvae in seeded sunflowen fields was Jur.e 10 and July 28 fon a mean dr:ration of 51 days.
The mid-point in the development of the second-instar was detenmined as the optimal time fon contnol of Larvae sirrce at that time most eggs had hatched and líttte foliage damage had occunned. Methods lv of accunately pnedicting this poínt, based on field obsenvations and
TU accumulations wene developed. Following completion of the fou::th instan, larvae entened the soil to pupate. The duration of the pnepupal and pupal periods combined was 16.9 days at 20oC, with an estimated ToLO of 7.4oC and TU nequir"ement of 2tt. The total developmental time fnom egg to adult was 44.6 days at 20oC.
Upon emengence fuom pupation, p::ehíbernation adults fed fon one to three weeks pnion to entry into the soil to ovenwinter". The mean date of finst appearance of pnehibernation adults was 'JuIy 26, 49 days or" 555 TUfs (7.4oC ToLO) aften the finst lanvae were obsenved.
Pnehibennation adults did not fly, nate on lay eggs.
A numben of diffe::ent predators attacked the differ"ent life stages of the sunflowen beetle. HippodamÍa tnedecimpunctata tibialis (Say) and Collops vittalus Say fed on eggs, Hippodamia convergens
Guenin-Menevil-le and g¡r:ysopa. caranea Stephens fed on eggs and lanvaeo Lebia atniventnis Say, Perilliodes bioculatus (Fab.) and Nabis sp. fed on lanvae, and Podisus maculiventnis (Say¡ and the blackbir"d, Agelaius phoeniceus phoeniceug L. fed on adults.
Fou:r' species of panasites vrene neared fuorn diffenent stages in the life cycle of the sunflower beetle; Myiopharus sp. fnom adults,
Enixestus winnemana Cr"awford f::on eggs, and Doryphonophaga macella
Reinhand and D. donyphonae (Riley) from larvae. v
Myiophanus sp.: ê tachinid reaned fnom adults, has two genenations per year on the sunflowen beetle. The panasite ovenwintens as a finst-Ínstan naggot in the abdomen of the ovenwinteníng host, migrating to the bnain in spning and eventually killing the host shontly before the time of normal emellgence. The parasite emel:ges about one month after. nonmal emergence of the hosto in time to panasitize the last of the posthibernation beetles to for"m the second genenation whÍch in tunn develops in time to attack pnehibennation beetles in late su¡nmerl and eanly fa1I. The maggots deposíted by second genenation adults form the ovenwintening population. In fÍeld collections of pnehibennation beetles oven thnee years, incidence of panasitism varied from 0.2 to 17.1 pencent. 0n1y one panasite was neared fnom each beetle. The hypenpanasiteo Pe::ilarnpus sp., þras ::eaned from pupanía of Myiophanus sp.
A one-month delay in spning emengence of the panasite followÍng that of the beetl-e pnovídes an oppor"tunity fon cont::ol of posthibernation beetles with nininal effect on Myiophanus sp.
Ênixestus winnemanara pteromalid, was reaned fnom eggs of the sunflower beetle. The life cycle of this panasite was completed in 16.1 days at 20oC, so sever.al genenations perî yean are possible.
Howeven, only one or possibly two genenations ane completed in any given sunflowen field because of the timited peniod during which host eggs are available.
Panasitism by E. winnenana nangeC up to 16.8 pencent in commercial sunflowen fields, while up to 65.7 pencent panasitism was vi obsenved in small plots used fon an oviposition tnial fon the sunflowen beetle.
Adults of E. winnemana are present ín the field at the same time as are adult;r ar" beetle. Contr"o1 of the host with """rrowen insecticides would. thus pose a hazand for the panasite. Donyphonophaga macella, a tachinid, panasitized la¡vae in all stages by subcutaneous lanviposition. Appeanance of the ovenwintened genenation is well synchnonized with that of the host, par"asitisrn oceunning within a week of first appearance of host lanvae. Females of
D. macell-a ar?e highly feeund, depositing a mean of 284.6 maggots over a
!4.2 day lanviposition peniod in the labonato::y. Supenpanasitism was common, but only one panasite successfully developed in each host 1arva.
The par.asite passes th::ough three instans, distinguishable by the size and shape of the nouth-hooks, the naggot r"enaining as a fÍr"st instan until the host larva completes deveLopment. The panasite develops napidly aften the host lan¡a enters the soil to pupate, kiIlíng the host in two on thnee days and emenging as a ner^r-genenation ad.utt about the same time as pnehibernation beetles. This generation is poor"ly synchronized wíth the host since the population of host lanvae would be declining napídly at the tíme of emergence of the new genenation of par.asites fncidence of panasitism in the field, over a five-year peniod, r:anged fnom 0.1 to oven 70 pencent, the majonity of the maggots being deposited du:ring the eanly lanva1 peniod when finst- and second-instan lanvae vrerle prevalent. D. macella tended to act in an inverse v11 density-dependent mannerâ; as the density of the host lar:vae. increased, the nelatíve impact of D. macella decr:eased. The hypenpanasite, Penilanpus sp. was neaned from pupania of D. macella. Control of host lanvae with insecticides would effectively el-ininate the panasite in any tneated. anea because D. macella initiates lanviposition veny soon aften first emergence of host lanvae.
D. donyphonae, a tachinid, was of rníno:: impontance as a panasíte of the sunflowe¡'beetle, nepresenting onJ-y 0.2 pencent of the panasites neared fnom host lanvae. Par"asites and pnedators are impo::tant natr:na1 control agents of the sunflowen beetle in Manítoba, and aid in suppnessing pest populations ín most yeans. v111
TABTE OF CONTENTS PAGE
ABSTRACT l-1
TABLE OF CONTENTS viií
LTST OF FTGURES xvii
LIST OF TABLES xxiii
ACKNO}ÍLEDGEMENTS xxxii
1. INTRODUCTION t
2. LITERATURE REVIEW 6
2.! The sunfLowen beetle, Zygognamma exclanationis (F.) 6
2.1.! Taxonomic status of the sunflowen beetLe and nelated specíes 6
2.1,2 Geogr:aphic distnibution and host neconds 7
2.1.3 Bionomics of the sunflowen beetle 10 2.t.3.t Ovenwintening and posthibennation emergence 10
2.1.3.2 Mating, oviposition and longevity 13
2 .1 .3. 3 Egg stage 16
2 ,7.3.4 Lanva1 stage t7
2.1.3.5 Pnepupal and pupal stages 1S
2.1.3.6 New-genenation adult 2t
2.1.4 Sunflower beetle contnol necommendatíons 22
2.1.5 Natr:::a1 enemies of the sunflov¡er beetle zó
2 ,7.5 .t Pnedatons zo 2.1.5 .2 Par"asites ôE
2.2 Myiophargs sp., ê tachinid panasite of adults of the srmflowen beetle 28 lx
PAGE
2.2.! Taxonomic status of the genus Myiophanus 28
2.2.2 Geognaphic distnibution and host ::econds 29
2.2.3 Biononics of Myíophanus 29 2.2.4 Impontance of Myiopharus in negulatíng host populations 30
2.3 Enixestus winnernana Cnawfor.d, a ptenomalid par"asite of eggs of the sunflowen beetle oz
2.3.1 Taxonomic status of Enixestus winnemana 32
-2.3.2 Geognaphic distnibution ar¡d host neconds 32
2.3.3 Bionomics of E::ixestus winnemana 33
2.3.4 Impontance of Enixestus winnernana in ::egulating host populatioãñ- 33 2.4 Donyl¡honophaga nncella Reinhand, a tachinid panasite of lanvae of the sunflowen beetle 35
2.4.7 Taxonomic status of Donyphorophaga macella 35
2.4.2 Geog::aphic distníbution and host necor:ds 35
2.4 .3 Bionomics of Do¡:yphor.ophaga macella 36
2.4.3.1 Ovenwintening and spnÍng emergence 36
2.4.3.2 I'fatÍng, lanviposítion and longevity 3B
2.4.3.3 Larva 40
2.4.3.4 Pupa 42
2.4.3.5 New-genenation adult 42
2.4.4 Importance of Dor)rphonophaga nacella in negulating host populations 43
2.5 The use of thenmal unit accumu-l-ations in insect contr:ol 46
2.5 .7 Pr.ocedr::res fon calcul-ating thenmal units 47 x
PAGE 2.5.7.1 Methods fon estimating the threshold tempenatu::e 48
2.5.7.2 Methods fon calculating TUts 49
2. 5. 1. 3 Appnopniate .peniod fon calculation of TU accumulations 52 2.6 The commencial sunflowen - histony and pnesent status in Canada 53
3. MATERIAL AND METHODS 56
3.1 Pnocedunes for: pnoviding and maintaining stock colonies 56
3.1.1 The sunfl-owen beetle - stock colony 56
3.1.2 Myiophanus sp. - stock colony 59
3.1.3 Enixestus winnemana - stock colony 60
3.1.4 Doryphonophaga macella - stock colony 61
3.2 Rate of development 63 3.3 Pnocedunes fon deternining incidence of pa::asÍtism of the sunflowen beetle 65
3.3.1 Detenmination of panasitÍsm by Myiophanu: sp. 65
3.3.2 Determinatíon of panasitism by E::ixestus winnemana 65
3.3.3 Detennination of panasitism by Donyphonophaga macella 66
3.4 Field sampling plots 1975 to 1977 67
3.4 .1 Ste. Jean, 1975 68
3.4.2 Letellien,1976 69
3.4.3 Ste. Jean, 1-977 69
3.4.4 Lowe Fanm, 7977 70 xi
PAGE
4. RESULTS AND DISCUSSION 72
4.1 Biononics of the sunflowen beetle in Manitoba 72
4 .1 .1 Ove::wintening 72
4.!.7.1 Overwintening stage and site 72 4.t :!.2 Repnoductíve condition of ovenwintening females 78
t+.1.1.3 Effect of snow cover on survival of ovenwinteníng adults 1976 to 1-977 83
4.7.2 Posthibernation emergence 87
4.1.2.1 Date of first emergence 1974 to 1977 87 4.1.2.2 Connelation of accumulated TU's to date of finst emergence 1974 to 1-977 88 4.1.2.3 Dunation and pattenn of posthibennation emengence 93 4.1.3 Initiation of posthÍbennation ovarian development and mating 95
4.1.3.1 InÍtiation of ovanÍan development in posthibennation females 99 4.1.3.2 Initiation of mating t02
4.1.4 Mating and egg-laying 104
4.1.4.1 Mating behavioun 106
4.1.4.2 Mating fnequency 106
4.1.4.3 Oviposition behaviou¡ 109
4.1.4.4 Frequency and pattenn of egg-laying 109
4.1.4.5 Fecundity !77
4.1.4.6 Dunation of the oviposition period 118
4.1.5 Egg stage 119
4 .1. 5 .1 Descniption 119 x].1
PAGE
4.7.5.2 Rate of development at various eonstant tempenatunes !20
4.1.5.3 Estimated ToLO and TU nequinements 723
4.1.6 La::val stage 726
' 4 .1 .6 .1 Descniption t26
4 .1.6 .2 Lanval behaviou:n and feedíng t27
4.1.6.3 Numben of instans 128
4.1.6.4 Lanval development duning labonato::y reanlng 131 4.1.6.4.1 Rate of development at vartous constant tempenatures t3t
4.1.6.4.2 Estimated ToLO and TU nequinements 135 4.1.6.5 Lanval developrnent duning field neanirrg 74t
4 .1.6 . 5 . 1 Dr::ration of the larval stage 143
4.1.6.5.2 Estímated TU nequinements 148 4.1.6.6 La::va1 development in sampling plots in commencial sunflowen fields 1975 to 1977 149
4.1.6.6.1 Ste. Jean, 1975 149
4.1.6.6.2 tetellier, 1976 1s1
4 .1 .6 . 6 .3 Ste . Jean , 1-977 154
4 .1 .6 .6 .4 Lowe Farrn , !977 158 4.1.6.6.5 Dunation of the lanvaI stage and estirnated TU nequinements 158
4.1.6.7 TimÍng of lanval- contnol 166 4.1.6.7,7 Testing various target dates at Lowe Fanm, 1977 t7t x].l-1
PAGE
4,1.6.7.2 Pnediction of date of L2-DT56 !77
4.L.7 Pnepupal and pupal stages tB2
4.7.7 .t Descníption tB2 4.7.7.2 Pnepupal and pupal development during labor.atony neaning IB2
4.1.7.2.7 Rate of development at va::ious constant tempenatures tB2
4 .1.7 .2 .2 Estinnted ToLO and TU neguinements 185 4.1.8 Development in the labonatory f::om hatching to adult emengence 1Bg 4.1.8.1 Rate of development at vanious constant tempenatunes 189
+.1.8.2 Estinated ToLO and TU ::equinements 190
4 .1.9 The pnehibernation adr:It 190
4.1.9.1 Descníption, feeding and behavioun Ig2 4.1.9.2 Finst obsenvation of pnehibennation adults and du¡ation of the pnehibennation peniod 193
4.1.9.3 Estímated numben of days and TU's nequined to complete development fnom hatching to emengence of pnehibennation adults 193
4.1.9.4 Numben of genenations peÌr yean 1g4
4.1.9.5 Factons affecting diapause induction 194
4.1.10 Survey fon natunal enemies 198
4.1.10.1 Pnedatons of the sunflowen beetle i-gB
4.1.10.2 Panasites of the sunflowen beetle 206 xiv
På.GE
4.2 Bionomics of Myiophar.us sp., a tachinid panasite of adults of the sunflower beetle 2t0
4 .2.1 Ovenwintening 210
4 .2.2 Lar:va 2tt
4.2,.2.7 Numben of instans 277
4 ,2.2.2 Lar.val behaviou:r and development 213
4.2.2.3 Duration of the lanval stage 215
4.2.3 Pupa 275
4 ,2.4 Adult 217
4.2.4.1 Panasite emengence in the labonator"y 277
4"2.4.2 Panasite emengence in the field, 1977 218
4 .2.4. 3 Mating 219
4.2.4.4 Lanviposítion 221 4.2.5 Incidence of panasitísm of adults of the sunflowen beetle, 1975 to 1977 222
4.2.5.1 Pnehibernation beetles 222
4.2.5.2 Posthibennation beetLes 222
4.2.6 Number. of gener.ations per year3 224
4.2.7 HyperpanasÍtes 225
4.3 Bionomics of Enixestus winnemana Cnawfor:d., a ptenonnlid panasite or effiõftäe sunffiwer beetle 226
4 . 3.1 Labor"atony neaning 226
4 . 3.1 .1 Oviposítíon 226
4.3.1.2 Rate of development of males and females 229 4.3.1.3 Rate of development at va::ious constant tempenatunes 229
4.3.1.4 Estimated ToLO and TU requirements 23I :{v
PAGE
4.3.2 fncidence of parasitisn of eggs of the sunfl-owen beetle collected in the field 1976 to 1977 232
4.3.3 Ovenwinteníng and spring emelrgenee 235
4.3.4 Numben of genenationb per year 236
4.3.5 Hyper.panasites 237
4.4 Bionomics of Do::yphonophaga macella Reinhand, a tachínid panaffiFffi õffisunftower beetle 238
4.4.1 Reaning in the laboratony 238
4.4.7.1 Mating 238
4.4.1.2 Lanviposition 238 4.4.1.2.7 Alignment of fi:rst-instan maggots in the uterus 239
4.4 .1.2.2 Behaviour duning lanviposition 240 4.4.1.2.3 Fecundity and lanviposition peniod 242
4.4.1.3 Lanval (maggot) stage 247
4.4.1.3.1 Numben of instans 2L+7
4 .4 .1 .3 .2 Lanval development 247
4.4.1.4 Pupal stage 249
4 .4.1 .5 Effect of diffenent constant tempenatunes on nate of development 250 4.4.1.5.1 Rate of development of males and females 251 4.4.1.5.2 Rate of developnent of pa::asite and host 2st
4.4.1.5.3 Estimated ToLO and TU nequirements ôEâ xv1
PAGE
4.4.2 Panasitism of sunflowen beetle lanvae by D. rnacella in field sanplíng plots 255
+.4.2,7 Ste. Jean , 1975 2s5
4.4.2.2 Letellien , 1976 260
4.4.2.3 Lowe Fanm, 1977 260
4.4.2.4 Supenpanasitisn 264 4.4.2.5 Relative incidence of parasitÍsm among instans 268 4.4.2.6 Synchnony of l. macella with the sunflower beetle 272
. 4 .4.2.6.1 Initiation of lanviposition, 1-975 to 1977 273 4.4.2.6.2 Response to host density, 1973 to 1977 273 4.4.2.6.3 Synchnony of new-genenation pa:rasites with host la:rvae 275
4 .4.2.7 OvenwintenÍng 278
4 .4.2.8 Hyper"panasites 279
5. SUMMARY AND CONCLUSIONS 2BO
6. REFERENCES ZgZ
APPENDTX 1. stages of oocyte development in the sunfrowen beetle, Zygognamma exctamationis (Genben et al 1979) 302 xv11
LIST OF FIGUFGS
Figu:re Page 1 Stages in the life cycle of the sunflowen beetle,
Zygognamrna exclamation_ís (e) e¿uft, (g) Eggs, (C) Lar"vae,
(D) Pnepupa, (r) Pupa 2 2 Defoliation by vanious stages of the sunflowen beetle,
Zygogfamma excLamationis, of the sunflowen, Helj,anthus
annuus (A) Damage by posthibennation adults pnoducing a
t'jagged-edge" effect on the leaves (B) Damage by eanly
instan lanvae pnoducing a rrshot-holett effect on the 1eaves
(C) Sevene defoliation by lanvae (D) Oamage to uppenmost
leaves by pnehibennation adults 4
3 Cages used du::íng studies on the bionomics of the sunflowen
beetle, Zygognamma exclamationís (A) plastic cylinder cage
(B) atuminium scneen cage (C) scneened emengence cage
(D) nyton scneen cage 57 4 Effect of snow coven on sunvival of ove:rwintened adults of
the sunflowen beetle, Zygogramma exclamationís 86
5 Deviations (days) of pnedicted fnom obsenved emengence fon
ovenwintening sunflowen beetles, Zygogran¡na exclamationis using mean emergence date and r¡anious thenmal unit
accumulation rnethods as pnedictons, 1974-!977 , 92
6 Ventnal view of abdominal stennites of female and male
Zygognamma exclamationís adults. The arnow índicates the
fifth stennite which is used as a sexing chanacter. 94 xviii
Figune Page
7 Cumulative emeugence of over:wintened female and male
adults of the sunfLower beetle, Zygognannma exclamationis,
fron the 7976-77 snolr coven study . 96
B Mating behaviour" of the sunfl'ower" beetle, ZygogramflEr exclama_tioni,s (A) male on fernale in mating position
(B) 'ríntnudíngil male pulling at the appendages of an rtín copularf mal-e whil-e the ttin copulat' male continues to nate with a female (C) two maLes fighting aften
female has gone tO7
9 Egg-laying pat tenn fnon the tine diapause ended r:nti1
the end of the ovíposition peniod for" 13 females of the
sunflowen beet Le, Zygognamma exclamatíonis 113
10 Egg-layÍng pattenn fon fou:r females of the sunflowen beetle, Zygognarrna excLamationis, kept outdoors at Glenlea, I'lanitoba, 1976 tt4 tt Egg-laying pattern for" twelve femaLes of the sunflower beetl-e, Zygognamma exclamationis, kept outdoons at
Glenl-ea, Manitobao Ig77 115 72 Days till hatching and nate of development of eggs of the sunflowen beetIe, Zygognanrna exclamationis, at constant
tempenatures 725
13 Head capsuLe widths of the foun lanva1 instans of the
sunflowen beetle, Zygognamma exclamatÍonís 130 xlx Figu:re page
14 Matenials used in neaning the sunflowen beetle, Zygognamma exclamationiÊ, fon the constant temperature trials (A) Seedling sunflowers used to near lanvae (B) ptastic
containers with moist venmiculite used to r"ean pupae !s2 15 Days nequir.ed to complete development and r^ate of development of finst-, second-, thind- and founth-instan
lanvae of the sunflowen beetle, Zygggrannna exclamationis,
at constant tempenatures 140
16 DeveJ-opment of lanvae of the sunflowen beetle, Zygognamma
exclamatíonis, Ste. Jean, Manitoba, 1,975 152 t7 Development of lanvae of the sunflower beetle, Zygognamma
glcle4qtjonís, LetelJ.ien, ManÍtoba, 1976 15s
18 Development of lanvae of the sunflowen beetle, Zygognamma
exclamationjls, Ste. Jean, Manitoba, tg77 t57
19 Development of lanvae of the sunflower: beetle, Zygognamma
exclamatíonis, Lowe Fanm, Manitoba, 1,977 160
20 Eggs and lanvae of the sunflower- beetle, Zygog:ramma exclanationÍs, collected duning fírst sampling and laten nesampling of plots at Lowe Fanm, Manitoba, !977 . t7g
2t Leaf damage on sunflowens, Helianthus qnnuus, at Lowe Fanm, Manitoba, on Jr:ly 13, 1977 foJ-Jowing manual nemoval of
lanvae of the sunflowen beetle, Zygognamma exclamatÍonls,
on: (A) June 2!, !977, (B) June 28, !977, (C) July 5, !977, (n) ;ufy 13,7977 tl; xx
Fígune Page 22 Days requined to complete development and nate of
development of prepupae and pupae of the sunflowen
beetle, Zygognannna exclamatiorÉrs, dt constant temperatures...l8g
23 Days nequi::ed to complete development and nate of
development for. the peníod fr"om emergence of finst-instan
lanvae to the start of feedíng by adults of the sunflowe::
beetle, Zygognamma exclamationis, at constarrt
tempe::atu:res 191
24 Pa::asites of the sunflowen beetle'- Zygogramma exclanationis
(A) ¡,lyiophanus sp. (s) trníxestus winnerËlna
(C) Donyphonophaga macella . . 2Og 25 Latenal- view of mouth-hooks of finst-instar" maggot of
Myiophanus sp. 2t2 26 Emengence of ovenwíntened adults of the sunflower beetle, Zygogr.amma exclamationis, and itrs parasite, Myiophanus sp.,
at Wínnipeg, Manítoba, 1977 220
27 Eggs of the sunflowen beetle, Zygognamma exclamationis
panasitized by Enixestus winnemana 227
28 Lanvipositíon sequence of Donyphorophaga macell-a dr:::íng parasitization of larvae of the sunflowen beetle,
Zygog::amma exclamationis (A) panasite seanching fon a host lanva (n) panasite stnaddling a host lanva (C) panasite
injectíng a rnaggot into a host larva 241 xxr
Figune Page 29 Latenal view of mouth-hooks of finst-instan naggot of Donyphongphaga¡nacellg. .248
30 Panasítísm of lanvae of the sunflowen beetle, Zygogranma
exclamationis, by Donyphonophaga nncella at Ste. Jean,
Manitoba, in 1975 257 31 Density of maggots of the panasite, Do::yphonophaga gacsffs,
and lanvae of the sunflowen beette, Zygognamma exclanrationis
at Ste. Jean, Manitoba, in 1975 2Sg
32 Parasitism of lanvae of the sunflowen beetle, Zygogr:amma excl-anationis, by Donyphonophaga macella at Letel1ien,
Manitoba, in 1976 262
33 Density of maggots of the pa:rasite, Donyphorophaga macella,
and lar"vae of the sunflowen beetle, Zygognamma exclarnationis,
at Letellien, Manitoba, in 1976 . . 269
34 Panasitísm of lanvae of the sunflowen beetle, Zygogr"amga
exclanratiolrso by Do:ryphonophaga macella at Lowe Fanm,
ManÍtoba, in 1977 . 266
35 Density of maggots of the panasite, Dor"yphor"ophaga macella,
and lanvae of the sunflower beetle, Zygognamma exclamatíonis, at lowe Fanm, Manitoba, in tg77 . . .- ,U,
36 Incidence of panasitism and supenparasitism of Zygog::amma
exclamationís by Donyphorophaga macella in plots at Ste. Jean in 1975, Letellien in 1976 and Lowe Farm, ín !977- .270 xxl_t
Figune page
37 Relationship between density of lanvae of the sunflowen
beetle, 4ygogramna exclamationis, and pencent
panasitization by Donyphonophaga macella . . 277 xxll_l_
LIST OF TABLES
Tabl-e Page
t. Mortality of the sunflower beetle, Zygognamma exclamationis,
neared on Helianthus spp. in the labonatony. (Fnom Rogens
and Thompson 19780 1980) 9
2. Published necoþds of pnedatons of Zygog::amma exclamationis . 24 3. Published neco::ds of par:asites reaÌred from beetles of the tnibe Donyphonini (Chnysomelidae:Chnysomelinae) in North
Amenica 26
4. Numben of adults of the sunflower beetle, Zygognamma
exclamationis, collected in emengence cages at two locatíons
in south-centnal Manitoba, 1974 and 1976 74
5. Numben of sunflowe:: beetleso Zygognamma exclamationis, collected at dÍffenent depths in soil at four" excavation
sites in southenn Manitoba .
6. Number of ovenwintening adults of the sunflowen beetle,
Zygognamna exclamationÍs, necovened'fnom soil in cages at
Rosebank and Ìfinnipeg, Manítoba, Octoben 1976 79
7. Date of collectíon, numben of females and oocyte development in pnehibernation and ovenwintening females of the sunflowen
beetle, Zygognamma exclamationis, 1973-1977 81
B. Effect of snow r:ernoval on the ovenwintening su::vival- of adul_ts
of the sunflower" beetle, Zygognamma exclamationís, llinnípeg,
1976-1977 8s xxÍv
Ta-b1e Pe oa
9. Date of first emergence and thenmal unit accurnulations
. (tu Acc. ) at finst emergence of ovenwinter"ing adurts of the sunflowen beetle, Zygognamma exclamationis, in volunteen sunfl0wen fields of south-centþal- Manitoba, tg74 to !977 g0 X0: Number and sex natio of posthibennation adults of the
sunflowe:: beetle, Zygogr"amma exclamatíonis, collected in the
field ín south-centnal Manitoba at ínte::vals from May 25 to
June 6, 1976 97 I!. Date, number^ of fenples and oocyte development in post-
híbennati.on females of the sunflows: beetl-e, Zygognamma
exclamationis, 1974-1977 100
1"2. Number of femal-es of the sunfLower beetle, Zygognamma exclamationis, with oocytes at a particul_an stage of
development when herd at diffenent temperatures fon 0-6 days
after emergence fnom hibennation 101 13. Dates of appeanance of adul-ts and eggs of the sunflower" beetle, Zygognamma exclamationis, in sunflowen fields in
south-centnal Manitoba, 7974-t977 103 14. Pneovíposition and ovipositiori peniodsr egg prod.uction,
numben of obser.ved matings, frequency of mating, and egg- layíng fon 13 pains (19 + 1cr) of the sunflowen beetle,
Zygognamma exclamationis in a controlled envinonment
cabinet at 25 t 2oC and a photoper.iod of 18L:6D 10g xxv
Table Page
15. Preovíposition and oviposition peniodsr egg pnoduction,
numben of obser.ved nratings, frequency of mating, and egg- iayÍng fon foun pains (tç + 1a) of the sunflowen beetle, Zygogramma exelamationis, caged on sr:nflowens out-of-doons
at Glenleao Manitoba in 1976 !70 16. hleovíposition and ovíposítion peniodsr egg productÍon,
numben of obsenved matings, fnequency of mating, and egg- laying fon t2 paíns (te + 1a) of the sunflower beetle,
Zygognamma excl-amationis, caged on sunflowe:: out-of-doo::s at Glen]-eao Manítoba in 1977 tt1, 77. Incubation per"íod fon eggs of the sunfl_owen beetle, Zygognanma g¡ç_lqqqti9lis, at foun temperatùr"es t2I
18. Pencent hatching in eggs of the sunflowe:: beetle, Zygognamma
exclamationis, at foun temperatures 1.22 19. Mean, standand enron and nange fo:: head capsule widths of the
four. lanval instans of the sunflowen beetle, Zygogrannna
exela¡nationis 1-29 20. Development tirne (days) of lar.vae of the sunflowen beetle,
Zygogx,amma exclamationis, at three tempenatures 134 21. Total la::vaI development time and pencent of total larval developmental time nequired fon each of four instans of the
sunflowen beetle, Zygognamma exclamationis, at thnee
temperatures 136 XXV]-
Table Page 22. Pe::cent mortarity for each larval- Ínstan of the sulflowen
beetl-e, Zygognamma exclamationis, at thnee temperatur.es ra7 23. Regnession equatíons, coefficients of detenmÍnation, estimated thneshold tempenature (toLo), and theonetical
thenmar unit (theor". TUts) nequir.ements fon d.evelopment of
lanvae of the sunflowe:: beetle, Zygog::amma. exclamationis, in
diffenent instans and combínations of instars . j_39
24 . Developrnent of lanvae of the sr:rrflower beetle, Zygognamma
exclamatíonis., in cages at Glenlea, Manitoba, July 7 to 27,
19 75 144
25. ÐeveJ-opment of lanvae of the sunflowen beetle, Zygog:ramma exclamationis, in cages at Gl-enleao Manitoba, June 10 to
July 8, !976 146
26. Development of .l-anvae of the sunflowen beetle, Zygognamma exclamationís, in cages at Glenlea, Manitoba, June 11 to
July 10, 7976 747 27. Numben of eggs, lanvae and adults of the sunflowen beetre,
Zygogramma exclamationis, neconded on sunflowen plants in a
sampling plot in a commencial- fÍel-d at ste. Jean, Manitoba,
1915 150 28. Numben of eggs, lanvae and adults of the sunfloi+er beetre,
Zygognamma exclamationis, neconded. on sunfrowen plants in a
sanpling plot Ín a commercÍal field at Letellien, Manitoba,
1976 . 154 xxvii
Table Page
29. Nurnben of eggs, lanvae and adults of the sunflower" beetle,
Zygogr.amma exclamationis, neconded on sur¡flowen plants irr a sampling pJ-ot in a comrnelrcial field at Ste. Jean, Manitoba,
7977 156 30. Number. of eggs, larvae and adul_ts of the sunflower beetle,
Zygog::amna exclamationís, neconded on sunflowe:r plants in a samplÍng plot in a commercíal_ fiel_d at Lowe Fanm, Manitoba,
1977 159 31. Calendan date ar¿d accumulated thenmal units (TUts) at fírst and last obsenvation of l_anvae of the sunflower beetle, Zygog::amma exclamationisn in thnee sampling plots in south-
centnal Manitoba, 1976-1977 162
32. Accumulated TUts and conresponding dates for the DT56 of the fou:: instars and the complete 1anval peniod of the
sunflowen beetle, Zygognamma exclamationis, at foun sampling
plots in south-centnal Manitoba, I97S-!977 164
33. Estimated numben of TUrs and days nequí::ed to complete
development of the fÍr^st three lanvar instars of the sunfrowen beetle, Zygognamma exclamationis, in fou:r sampling plots in
south-centnal Manitoba, 1975-1977 165
34. Numben of lanvae of the sunflowen beetle, Zygognamma
exclamationis, necovelled on July 13, !977 fnom plants at
Lowe Fanm, Manitoba, following manual_ nemoval of lanvae
vanious dates fnom June 2t to July 8, !977 772 xxvJ.L1
Table P: oa -Eòv 35. Accumulated the¡.mal uníts (TU's) and days fnom the date of fir"st hatch to the DT56 for" second-instan l_arvae of the sunflower" beetle, Zygognamma exclamationis, at fou:t sampling
plots in south-central Manitoba, tgTS-1977 t7g
36. Fnedicted date and errolr in pr:edíctiorr for the DT5g of the
second lar:va1 instan of the sunflower. beetle, Zygog::amma qxglanationis, at foun sarnpling plots in south-central_
Manítoba.- 1975-1977, using foun methods 181 37. Developmental time (days) of pr.epupae and pupae, and times
fon vanious combinations of immatr¡r.e stages of the sunflowen
beetle, Zygog::amma _eryIamglio4s, at th::ee temperatules 184 38. Percent mor"tality for pnepupae, pupaeo and combinations of
irnmatu::e stages of the sunflowen beetle, Zygognamma
exclamatig¡¡is, at thnee tempenatunes 186 39. Regnession equations, coefficíents of detenmination, estimated threshold temperatunes (ToLO), and theoretical thenmal- r¡nit (theor. TUrs) nequirements fo:: development of pnepupae, pupae and combinations of immatu:re stages of the
sunflowen beetle, Zygognamma exclamatíonis . . tg7 UO, Calendar date and accumulated thenmal units (tUts) at finst obsenvation of lar"vae and new-gene::ation adults of the
sunflower. beetle, Zygog::amma excl-amationis, in thnee sampling
plots in south-centnal Manitoba, 1976-1977 1g5 xxl_x
Table page
41. Pencent diapause of male and female adul_ts of the sunflowe::
beetle, Zygognamma exclamationís, reared fnom lar"va1 emergence to adult at diffenent combinations of photoperÍod and tempenatur:e
42. Pnedatons of vanious stages of the sunflowen beetle, Zygogramma exclamationis, in south-centnal Manítoba, tg74-
1977 . 199 43. Numben of pnedatons obsenved duning sampling fon the sunflowe:: beetle, Zygog:rámma glcl3matignie, at a plot at Ste. Jean, Manitoba, 1975 20r
44. Numben of pr"edato::s obsenved du:ring sampling fon the sunflower" beetle, Zygognamra exclamatÍonÍs, at a plot at Letellíen,
Manitoba, 1976 202 45. Number of pnedatons obsenved duníng sampling fon the sunflowen
beetle, Zygognamma excramationis, at a plot at ste. Jeano
Manitoba, 1977 203
46. Numben of predators obsenved during sampling fon the sunflowen
beetle, Zygognanrna excramationis_, at a plot at Lowe Fanm,
Manitoba, 1977 204 47. Panasites neared fr"om vanious stages of the sunflower:
beetl-e, zygpgremma excLamationís, in south-centnal Manitoba,
1974-lgi?;¡..rr 2OB 48. rime ÍätêFWi (deye) f,rom nemoval of sur¡frowen beetle, Zygggi'amma exclamationis, fnorn cold stonage to death of beetJ-e, áäd and emergence þupation of the panasiteo Myiopharus sp.. 216 xxx
Table page
49. Pencent panasitism by Myiophanus sp. of pnehibennation and
posthÍbennation adults of the sunfrowen beetle, Zygognamma
excl-amatíonis, in south-centr.al Manitoba, ITTS-I977 . 22A 50. Days requi::ed to complete deveiopment of the parasite Enixestus winnemana on eggs of the sunflowen beetle,
Zygognamrna gxclamationis, at thnee tempenatunes 2gO
51. Pencent panasitism by Enixestus winnennna of eggs of the sunflower: beetle, Zygogr.arrna exclamationis, collected at
Glenlea, Manitoba in 1976 and 1977 . 283 52- Pencent panasÍtism by Enixestus winnemana of eggs of the
sunflov¡er: beetre, Zygognamna exclamationis, collected fnom two
sunflowen .fíefds Ín south-centnal Manitoba, tg77 . 2g+ 53. Lanvipositíon peniod, totar and mean daily pnoduction of maggots by Donyphonophaga macell-a, and pencent par"asitísn of
finst- and second-Ínstan lanvae of the sunflowen beetJ-e,
Zygogramma exclamationis 244
54. rncidence of pa::asitism and degnee of slpenpar-asitism by Donyphonophaga macella among finst-, second-, thÍnd- and fou::th-
instan larvae of the sunflower beetle, Zygog::anrna exclamationis, in the labonatony . Truu 55. Developmental tÍme (days) of males and. fernales of
Donyphonophaga macella, at fou:: temperatures 252 56. Regnession equations, coefficients of detenminationo estimated thneshold tempenatues (ToLO), and theonetical therrrar unit xxxi
Tabl-e Page
(Theor. TUts) r'equir"ements fo:: development of male and
fernle Doryphonophaga macel-la . 254 57. Pencent panasitism of finst-, second-, thind- and fou::th-
instar: l-a::vae of the sunflowen beetl-e, Zygognamma exclamationis, by Donyphonophaga macella in a sampling plot at
Ste. Jean, Manítoba, 1975 256
58. Per"cent panasitis¡n of finst-, second-, thind- and founth-
instan la::vae of the sunflowen beetle, Zygog::amrna
exclamationis, by Donyphor.ophaga macella in a sampling plot at Letellien, Manítoba, 7976 26t 59. Percent par"asitism of finst-, second-, thir:d- and fot¡r'th-
instar lanvae of the sunflowen beetle, Zygognamma exclamationis by Donyphonophaga macella in a samplíng plot at
Lowe Fa::m, Manitoba, 1977
60. DistrÍbution of maggots of the parasíte, Donyphonophaga
nacella, among the diffenent instans of the sunflowen beetle, Zygqgqq4lq exc a¡gtíonis, fnom field plots at Ste. Jean in
1975, Letellien in 1976, and Lowe Fanm in 1977 269
61. Date on which panasítism by Donyphonophaga macell_a was finst
noted on larvae of the sunflowen beetle, Zygognamma
exclamationis, during the spning of 1975, 1976, and !g77 274 62. Incidence of panasitísm of lanvae of the sunflowen beetle,
Zygognamma exclamationis, by Donyphonophaga maeella in seven
sunflower. fields in south-centnal Manitoba, tg73-!977 . . 276 xxx]-I
ACKNO}ÍLEDGEMENTS
Sincene thanks ane extended to my supervison, Dn. P.H. llestdal , Research Station Agnicultune Canada, I,linnÍpeg, for his guidance, suggestíons and discussions through the counse of this studyo and most especially fon the long hours spent ín r.eviewing the thesis. I am also grateful to the othen membens of my committee; Pnofesson A.G. Robinson,
Depantment of Entomorogy, and Pnofesson B.R. stefansson, Depantment of P1ant Science, for: thein advice ana cniti-cal eval-uation of the thesis.
Special thanks a::e due to the following people at the Resea::ch
Station, Agniculture Canada, VÍinnipeg: Dr. G.H. Genber"n fon his advíce, vaLuable discussions and fniendship; Mr. R.!I. Sims for nany of the photognaphs presented in the thesis; and Dn. li.C. McDonald, Dinecton, fon penmissíon to use the facilities and equipment of the Research
Station du::ing the study. The crose coope:ration of othen membens of staff of the Reseanch Station also is gnateful_ty acknowledged.
Ï gratefully aekrrowledge the financial assistance pnovided by: an Ag::icultur"e Canada Openating Gnant to Pr.ofesson Robinson (19?4 to
1978); a univensity of Manítoba Gnaduate Fett-owship (rg7s/77); and a National Reseanch Council Postgr"aduate Schola:rship (1-976/77 and 1977/78).
I also thank Miss Cathy Sheanen and Miss Jerurifer Shamess fon thein technical assístance.
I thank Dr,. J.A.G. Howe, Supenintendent, PFRA Tnee Nunser.y,
Indian Head, Saskatchewan, fon pnoviding the time and facilities to allow me to complete the thesis. Special thanks to Mrs. Shanon Banboun, xxxr_l_l_
Mns. Betty Lowey, ðd Miss Jeanette Pelletier for. typing vaníous d:rafts of the thesis.
Finally, I wish to sincenely thank my wife, C1aine, and son,
Richand, fon thein encounagement, r¡rdenstanding, constant faith and fonbeanance. T. INTRODUCTION
The sunflowen beetleo Zygog:ranma exclamationis (F.) (Coleoptena: chrysomelidae), is an oligophagous insect which feeds on serected. rnernbens of the genus Helianthus, the''rnost ímportant of which is the cul-tivated sunfrowen, Helianthus annuus L. (Rogens and Thornpson 197g, 1980). This beetle has been neponted foom the canadian pnaÍnies
(criddte 1922; I{estdal and Banrett 19ss), the nonthenn Gneat plains states of the u.s.A. (schulz 1978), Montana (cooley 1918), Arizona
(BnÍs1ey 1925), Nebnaska (powetl 1932), Kansas (Dougtas 1929; !üalker
1936), Utah (Know1ton and Smith 1935), and Texas (Rogens tg77). As predÍcted by criddle (tszz)o the sunflowen beetle hâs spnead fnom native plants to cultÍvated sunflower. ft is now considened one of the five nost ínpontant ínsect pests of conrnencial sr:r¡flowen Ín Manitoba (llestdal and Bannett 1g5s) and one of the six nost inpontant ou"a" o, srnflowens Ín Nonth Dakota (Schulz and Lipp 1969), but in the southenn sunflowen g::owing ::egions of the u.s.A., it is not economically impontant (Rogens and rhonpson 1980). llestdar È.r (192g) neponted ::eduetions of up to 30 pencent in the seed. yíerd of sunfl-owens due to deforiation by the beetre. Extensive use of insecticides has been nequi:red in l4anitoba to contnol outbneaks of the pest on th:ree occasions - 1952, 1957-59 and 1971-74 (lÍestdal 1925). cobia and Zimmen (fgzg) neponted economically inportant populations of the beetle
rn Manitoba, the sunfrowen beetle ovenwinters as an adult (Eigune 1a) in the soil and emenges in the spning about the time Fígr::le 1 . Stages in the 1ífe cycle of the sunflower: beetle,
Zygog::amma exclamationis
(A) Adult(xe)
(B) Eggs ( x 14 )
(C) Lanvae ( x 4.5 ) (n) Pnepupa(xz)
(E) Pupa ( x7 )
e
sunflower seedlings emenge (Ïlestdal and Ba:rnett 1955, lfestdal 1gZ5). shontly after emergence, the beetles begin to feed on the leaves of
seedling sunflowens, (Figune 2a), nnte and lay eggs (Figr:::e 1b) r+hích hatch within a week. The ranvae, which are a dulr yellow-green (Figune 1c), feed on the leaves, mainly at night, congregating among
the bnacts of the flowen bud and ín the axils of the leaves duning the (llestdal day 1975). InitiaL feeding by the lanvae gíves the 1eaves a shot-hole appeanance (Figu::e 2b). Duning severe infestations, the
lanrrae ean completely defoliate the plant (Figur"e 2c). The lanvae are pnesent in the field fon about six weeks aften whích they enten the
soil and fonm eanthen cel-ls in which the pnepupal and pupal stages ar?e passed (Figunes 1d and 1e); the pupal peniod lasts about 10 days to two (llestda1 weeks 1975). New-genenation adul_ts emenge and feed fon a shont time on the uppenmost leaves of the plant (Figune 2d) before neentening the soíl whene they pass the winter: (lfestdal 1g7s). Thene
is only one genenation pen yean in ManÍtoba (llestdal and. Barnett 1955). There are few pubrished neconds of natunal enemies of the sunflowen beetle. although ![estdal (1975) speculated that natu:ral contnol factons l^telre nesponsible fon naintaining the beetle population at 1ow
Levers in most years. rn Manitoba, westdal and. Bannett (1952) neponted that Lebia atniventris say (coleoptena:canabidae) and a pentatomid bug (Hetenoptena:pentatonidae) rea on lanvae of the sun- flower beetle, and that lady beetles (Coleoptena:Coccinellidae) and aphid lions (Neunoptena:chnysopidae) were pned.aceous on the eggs.
Walken (1936) in lGnsas, also noted aphid l-ions feeding on the 1anvae. Figune 2. Defol-íation by various stages of the sunflowen beetre, Zygogna¡nna exclamatíoniso of the sunflowen, Helíanthus annuus
(A) Damage by posthibernation adults pnoducíng a t'jagged-edget' effect on the 1eaves (B) Damage by eanly ínstar" lanvae producing a 'rshot- holetr effect on the 1eaves
(C) Sevene defoliation by 1a::vae (D) Damage to uppenmost leaves by pnehíbennation adults
Thene are no published accounts of panasites being neared fuom the sunflowen beet]e.
sÍnce a tho::ough knowredge of the Lífe histony and natural contnol factons is basic to any pest. nanagement pnogr.an, the pnesent study was unde::taken, finstÌy, to obtain detaíled infonmation on the bíonomics of the sunfrowen beetle ín l,lanitoba, and, secondly, to study the life histonies of the most impontant panasites of the beetre, namely, Myiophanus sp. (Diptena:Tachinidae) a par.asite of the adurt, Enixestus winnemana Cnawfond (Hymenoptera :Ptenomalidae) a pa-nasite of the egg, and Doryphor.ophaga macella Reinhand (Diptena:Tachínidae) a par"asíte of the lanva. Data obtained fuom these studies wene used. to pr:edict the occunnence of the va::ious life stages of the beetle, to PlsoPose the most effective timing fon chenical contnot applicatíons, and to help explain fluctuations in the density of the beetl-e. 2. LITERATURE REVIE}J
2.t The sunfl-owen beetle, Zygogramun exclamationis (f. )
2.1.1 Taxonomic status of the sunfl.owen beetle and nelated species (_1972) wircox neviewed the taxonomy of the chnysomelinae, a
Subfamily of the Family Chr^ysomelidae. In the neview Wítcox listed 1g species in the genus Zygognamma Chev., one of which was the sunflowen beetle, Z. exclanationís (F.). He placed the genus Zygogr.amma in the Tnibe Donyphor:ini along with the genera calIig::apha chev., LeptÍnotarsa
Sta1, I¿bidomera Chev., and Chrysolina Matsch
The sr:nfl-owen beetle is the best known species ín the genus Zygog::amma, pr.obably because it is the only memben of the genus that is an economic pest. The onry othen specíes in the genus about which thene is any pubríshed biological informatíon ane Z. sutr:¡aris (F.)
(ripen 1975) and z. disnupta (Rogens) (liper. tgTg), and Z. tontuosa
(Rogens) (Goeden and Ricken tg79), all of which feed on r:agweed,
Amb::osia spp. Some of the mone notewonthy membens within the Tnibe Donyphonini incrude the colonado potato beetle, Leptinotansa decenlineata (Say), the mÍlkweed leaf beetle, Labid.omena clivÍcollis
(Kby.)o the wil-low leaf beetle, callignapha murtipunctata bigsbyana
(Kby.), and two species of chnysoling, c. quadnigenina (suffn.) and c. hypenÍci (Fonester') imponted to North Amenica to control the Klamath weed, HypenicÍum penfonaturn L. I
2.1.2. Geographic distní.bution and host r:econd.s The sunfrower beetle is native to Nor.th Amenica as is its prirnany host the comrnon sunflowen, Helianthus annuus (L.) (Wilcox !g72, and Heisen 1976). The beetle has been necorded fuom most states and. provinces of the Gneat PÌains a::ea of Nonth AmenÍca. cniddle (1922) noted that the beetle was comnon and widespnead in Manitoba. He found it feeding on va:rious species of wild sunflower, most corunonly Indian potato' H. giganteus L.o and the pnainie sunflowen, H. petíolanis Nuttall. cniddle noted that the beetle had spnead to cr:ltivated sunflower:s whene it bned as neadily as on wild species. llestdal (1975) included the sunflowen beetle in his review of insect pests of commenciaL sunflowens Ín the pnainie pr"ovinces of Canada. Schulz (1g7e) claimed the beetle to be the pnedominant leaf-feeding species of sunfl-owen in the nonthenn sunflowen-gnowing negion of the Llnited states, that is Nonth Dakota, Minnesota and south Dakota. cooley (191g) neponted the beetle fuom H. annuus in Montana. powell (tssz) stated rtnathen that the beetl-e was abundantrf oven nìost of Nebr"aska. He collected specimens fnom pnainÍe sunflower, potato, Solanum tr:berosum L., white cloven, Melílotus alba Desn., and .tr"tr.rffi. (7929) Douglass coll-ected the beetle fnom the pr.ainie sunflowen and comncn sunflowen, H. annuus (Ienticulanis), in Kansas, whÍle f{alken (1936) found aduJ-ts and Ia:evae on isolated sunflowen plants in the vicinity of Manhattan, Kansas. l(nowlton and smith (rgss) neponted specimens f-::om Bracksmith Fonk canyon, utah, but no host necond was given. Bnisley (fSZS) cotlected the beetle fuom the pnainie sunflowen I
nean Camp Vende, Arizona. Rogens (1977) and Mitchel1 et al (192g)
fou¡rd J-ow populatíons of the beetl-e in fiel-ds of cultívated sunflowen
in Texas. Rogens (7977) found the sunflowen beetl-e common on woorry leaf bu:nsage, Fransenia tomentosa *lt, in the panhandle of Texas in
the spning of 1976 befone srurfl-ower emenged. He concluded that the southenn range of the beetle appanently cuts actîoss the nonthwestern thind of Texas.
rn laboratony studies in Texas, Roger"s and Thompson ( !g78, 1gg0) scneened 25 species of wild Hetianthus and. one cultivated oilseed
vaniety of H. annuus fon nesistance to the sunflowen beetre. They
wêne looking fon genetic retenial for use in a sunfrowen bneeding
prcgram. Beetles developed, fuom the finst instan to the adutt stage,
on only seven of the wild species and thene was a lowe:: survival nate
in six of the seven than on curtivated sunflower" (rabte t). The
pnâi-::ie surrflowen was the only wild specíes whene s¡:nvival vÍas not
signifícantl-y lowen than on the cultívated. sunfl-owe::. A few rar.vae
developed on the Jerusalem antichoke, H. tubenosus L. and the ashy
sr:nflower, H. moll-is Lam., but died befone neaching the ad.ult stage.
Rogers and Thompson (1979) also neponted that newly_emenged females that wene fed on brue weed, H. cilianis panadoxical Dc., the sunflowen, ,.o*J {. Panadoxus Heisen, the wiltow-leaf sunflower, H. sa1Ícifolius Dietre., and the Jenusal-em artichoke pnoduced no eggs, wheneas females fed on the cultivated sunfl_owen (UyUnia 996) averaged 11020 eggs each. The longevity of both males and ferales nnintained on blue weed, panad.oxical sunflowen and willow-Ieaf sunflowen was significantly reduced fuom that Table 1. Montality of the su¡rflowe:: beetle, Zygognarmna exclamationis, neaned on Helianthus spp. in the tabõra@- Thompson I$ZBT ãõt
Helianthus sDec Yo mortalityl nepo 1"978 1980 angusticfol-ius L. sÌ{amp sunflowen g 6fsfs anr¡uus L. comnon sunflowen 94ts:.L angophyllis Tonney and Gnay silver'leaf sunflowen g4:tfs debilis Nuttal weak sunfLowen 84o,r'^t panadoxus Heisen panadoxical sunflowen g g fsfs petiolanis Nuttal pnainie sunflowen 52 praecon (Heise::) spp. hÍntus g 2?t.i¡ (check) annuus L. Hybnid 896 35 24
montality finst- nstan to adult enengence. z'.'z'sgignlf icantly diffenent fnon the check (P=0.01) in the same column. 10
of adults maintained on cultivated sunflower wheneas this was not the
case with females fed on Jerusalem antichoke. Ma1es fed on Jenusalem
antichoke, howeve::, lived a significantly shonter time than males fed on cultivated sunflowen.
2.!.3 Bíonomics of the sr¡nflowen beetle
cniddte (t922) pnovided the finst details on the biology of the
sunflowen beetle in Manitoba. lfalken (1936) nlade some corrnents on the
beetlets l-ife cyele ín Kansas. l{estdal and Banr:ett (1955) and Westdal- (1975) pnovided the most recent neport of the biology of the beetle in the Canadian pr"ainies. Schulz (fgZg) nevÍewed the bíology of the sunflowen beetre based mainly on the above papens. Rogers (1977)
published the finst detailed data on the bionomics of the beetle based on rabonatory reanings. He also neponted on some field stud.ies, but
drew few conclusions because populations with which he wonked wene low. scneening tníals with the sunflowen beetle on vaníous species of Helíanthus, conducted by Rogens and Thompson (!g7g, 1gg0), pnovided
additional l-abonatony data. Gerber" et aI (197g, tgTg) described the r:epnoductive physíology and the nepnoductive cycle of the beetle in Manitoba, but since rnuch of the data was accummul-ated in connection
wíth this thesis, and will be p::esented rateno these papens wilr not be included in this neview.
2.t.3.t Ovenwintening and posthÍ-bennation emergence
rn Manitoba, the sunflowen beetle has been neponted to over- winten as an adul-t in the soil (Westdal and. Bannett 1955) and in l(ansas 7l it was noted to overwinten as a pupa in the soir (l{al-ken 1936). Rogens ftglz) gave no indication of the ovenwintening stage o:: rocation in
Texas. Zygog:rarrna suturalis. has been r"eponted to overwinten as an adul-t in Ohio (Pipen 1975). z_. disqLrptar in Texas, overwinters as an adurt in a pupar chamber. forrned by the second-genenation pupa (pipen
1978). Goed.en and Ricken (fgZg) neponted that Z. tortuosa ovenwintened as an adurt in southenn califonnia. other species ín the Tnibe
Donyphoníni which also overwinten in the adult stage include: the Colorado potato beetl-e (eibson et al t92S); the willow leaf beetle (oaviautt 1941); and the mitkweed leaf beetle (Eickwort IgTr). Although thene is no published infonnation available on the depth at which the sunflowen beetle ove::wintens in the soi1, the:re is some infonrnation fon the colonado potato beetle. Gibson et al (1925) found that soil- t5rpe had an effect on the ove::wintening depth of the potato beetle. rn cold, damp clay loam, beetles wer:e found within two inches of the sur:face and none below six inches, while in l-oose sandy soíI only a few hundned feet away, none wene found at less than 14 inches and some at 17 inches. Generallyo they obsenved beetres over"wintening at depths of six to eight inches with lessen numbens at greater depths. Mail and salt (1933), in Montana, neported that the colo::ado potato beetre could go down to mone than five feet ín loose sand and they consenvatively assumed a hiber'¡ratíon depth of t2 to 14 inches. Stnickland (1937) ind.icated the avenage hibennation d.epth in Albenta to be 18 inches. t2 No ínfonmation was located to ind.ieate ovenwinter,íng montality fo:r the sunflowen beetle, howeven, thene are some neponts dearing with the Colonado potato beetle. Gibson et al (fSeS), in field cage studies in New Bnr¡nswicko found winten montarity nates between 65.g and g9.2
pencent. Hancount (1971), ir onta:rio, found. montarity rates between
12.5 and 69.9 pencent fon híbennatÍng adurts excavated in the eanly spning between 1961 and i-967. Maíl and Salt (1933) speculated that the chíef limiting facton in the nonthenn spnead of the colo::ado potato
beetle $ras success in híbennation. They considened. hibennation depth, sno¡tr coven, and soil and ain tempenature to be the nain factons
affecting hibennation success. SÐ:ickland (19g7) adl.ed soil moistur.e
levers to the J-íst, indicating that nontarity was highen at high moistune leve1s than at tow moistr¡:re l-eve1s.
rn Manitoba, ovenwintening adurts of the sunflowen beetle emer.ge in the latter part of May about the time sunflower seedlings
begín to emerge (westdal et al t976, lfestdar and Bannett 19s5). rn Texas, Rogens (!977) noted adults on woolly leaf bunsage in the spning
of 1976 befone sunflower emenged. pipen (1g7S) obsenved adults of Z. sutturaris in eanly spning when nagweed. plants vrerae only 2 to 5 cm ta1I. Pipen (rgze), in Texas, reconded adults of L. disnupta ín eanry June when Ambnosia psirostachya D.c. was 20 to 2s cm in height. fn califonnid, z. tontuosa $ras nepor3ted to emenge foIlowíng nainy peniods (Goeden and Ricker 1979). Gibson et al (1925) neponted that, in
diffenent locatities thnoughout Canada, the Color.ado beetle emenged between May 23 and June 5, and indicated that emengence was dinectly 13 nelated to soil tempenature. They found that the spning emergence
period fon the Colonado potato beetle in New Bnunswíck lasted 19 days, and speculated that thÍs extended emengence peniod was due to varying soil ternpenatures caused by diffenent soil- types and diffener¡t 'to exposures to the sun; beetl-es crose the soir sr:rface would become warmed up and active sooner than those at lowen revels.
2.!.3.2 Mating, oviposition and longevity Vlestdal (feZS) stated that mating started. shontly aften posthibennation adults emerged. Rogens (t977) found. that mating
started appnrximately one week aften eclosion in a labonatory neaned
colony. He noted that mating vlas fuequent and continued thnoughout the
oviposition peniod. Fnequent and rnultiple matings have also been noted
by Pipen (rgzs) fon Z. suturalís, by pipen (197g) for Z. disnupta, and by Gir".ault (1908) fon the Col_onado potato beetle. pipen (tgZe) atso
obsenved that the numben of matings declined steadiry in f-nequency as the female aged and that males and females neadily accepted dÍfferent r¡ates. Detailed descriptions on courtship behavioun have been given fon Z. suturalís by Pipen (1975) and fon Z. disnupta by pipen (1978).
No descnÍption on the countship behavioun of the sunflowen beetle could be found.
Rogens (t9ll) found the pneoviposition peniod fon the sunflowen
beetle, nea::ed at 27 ! 2oC, to be 15.6 t 0.9 d.ays, wheneas Westdal and
Barnett (1955) noted the start of egg-laying appnoximately one week after the ovenwintening adults wene fínst obsenved in the fierd. 14
Aceonding to Westdal et aI (1976) eggs would thus be pnesent in the field in tate May on ;; June; Cniddie (tgzz) and !Íalke:: (tsso¡, obsenved eggs in the field from l_ate Jrihe to mid-.Tuly. The sr-rnflowen beetle deposits eggs síngly, not in crustens (Westdal 1975; Rogens 7977) althougtr it has also been noted to tay eggs
in innegular rolrs (Cniadte tg22). Eggs have been obsenved on su¡¡flowen stalks and on the undensides of the leaves (vlestdal 1975) although in
lesser: nurnbens on the latten (cnidale !922). c?iddle (tgzz) also noted
that fe¡nares tended to lay eggs in natunar grooves when such we:re
present. L. sutllralÍs has been noted to lay eggs in clustens of two on th:ree on the undensídes of yor:ng nagweed leaves usually nean the tip (rÍper 1975) . L- disnupta nepontedly also lays eggs in clustens, but in grloups of two to five and sometimes up to 1g (eipen lgz8). z_. tor.tuosa
laid eggs Ín clustens averaging 7.9 eggs pen clusten (Goeden and Ricken
1e7s ) .
There are only two neponts in the litenatune on the fecundity of the sunflowen beetle. Cniddl e (ilSZZ) observed that, one female, in
captivity, laid l-16 eggs, but stated that she had pnobably deposited a
numben of eggs befone captune and, thenefore, estimated a total egg pnoduction of at least 200 pen female. He also estinated an oviposition
peniod of two ol1 ¡nore weeks. Rogens (L977) found that feunles neaned.
in the labonatony at 27 ! 2oc raid an average of 14.g t 1.1 eggs pen day oven an oviposition peniod of 75.6 t 10.5 days fon a total pnoduction !,027 ! tlz.6 eggs pen femare. He noted one fecund female that laid. 4,131 eggs in 185 days. pipen (1925, 19Zg) and Goeden and 15 Ricken (1979) have provided egg-Iaying data on othen species of zygograurna neaned in the labonatony. Acconding to pipen (tg7s), z.
suttr¡a1is oviposíted over an average of 33 (nange 22_42) days with an
average daily pnoduction of 13 (nange 0-32) eggs pen female pen day fon a total egg p::oduction (nange of 165 145-569) eggs pen female, and !. disnupta pnoduced an average of 9.0 t 0.7 (nange 1-40) eggs per egg_
laying day oven a mean oviposÍtion peniod of 3?.3 t 4.7 (nange 7_?g)
days fon a total pnoduction of 262 t +3 (nange 27-g4S) eggs pen fernale (eipen 1978). L. tontuosa pnoduced an avenage of 1s.B t 11.9 (nange 1-48) eggs per egg-laying day oven a mean oviposition peniod of 10.5 1 2.6 (range 7-18) days for a totat pnoduction of 145 1 oz (nange 2t-242) eggs per fennle (Goeden and Ricken 1929).
Thene ane only two r"eports on the Ìongevíty of sunflowen
beetle adults. Rogens (1977) stated that labonatony neaned (ZZ ! ZoC) females and males lived 91.0 t 10.9 and 92.9 t 8.3 days, respectívely, when nea::ed on a cultivated variety of sr¡¡flowen. Howeven, females fed one of forrn species of wird Helianthus lived an avenage of 11 to 68 days, wheneas rnales lived 18 to s9 days (Rogens and Thompson 19zg).
Pipen (1975, 1978) neponted the longevity of Z. suturalis to be about two months, and the J-ongevity of Z. disnupta to be 49.g 1 g.4 (nange 12-83) days fon mares and 58.4 t 5.4 (nange 10-111) days for fernales.
Goeden and Ricker, (197g) r.eponted the longevity of z. tontuosa to be
104 1 40 (nange 36-172) weeks fon mal_es and 131 I SO (nange 34_197) weeks fon fernares. They found that at intenvals of one-10 months, su¡vivons resurned feedÍng fon one to several weeks, then became Ib
inactíve again. Thene ane reponts that some ad.ults of the coronado potato beetre may successfully híbennate thnough a seeond winten (Gibson et a1 1925).
2.1.3.3 Egg stage
cniddre (1922) descnÍ-bed the sunflowen beetle egg as being
erongate-cylindnical, about thnee tines as long as wide, and. slightly
tapening towands one end. He fu::then stated that it is mod.eratery densely Punctate so that spaces between the punctunes fonm a r¡et-IÍke
su:rface, and that the egg was whíte on gneenish tunning to onange
befone hatching. lfalken (fggO) descnibed the egg as being 2 to O mm
long and whitish-yelIow in coloun. Westdal (fgZS) descnibed the eggs
as cigan-shapedo ye1low to onange, and 1.5 to 2.0 mm 1ong. pipen
(1975, 1978) ne.ponted that eggs of z. sutu:ralis wene yerrowish-onange
and measured 1.45 to 1.65 mn aorrg by a.ra a. 116 mm wide and that eggs of L. dÍsr"upta wene also yelrowish-onange and measuned 1.57 1 0.01 mm by 0.69 t 0.01 mm. Goeden and Ricker (tglg) stated that Z. tortuosa had yeIIow-orange to salmon pink eggs that measur"ed 1.36 t 0.05 mm by
0.60 t 0.03 mm. llalken (1936) neponted that the incubation peniod ín the field was foun to five days, wheneas ÏIestdaL (fSZS) neponted hatching in about one week. Rogens (1977) stated that at 27 ! 2oc, eggs hatched in 5.4 t 0.1 days. Pipen (!977) neponted that z. disnupta eggs hatched in
6.26 (nange five to seven) days when r"eared at 24 ! zoc. Goeden and Ricken (tgl1) reponted that Z. tontuosa eggs hatched in thnee to four days at 27 ! to1. Davjaul-t (1941) found that for" the wíllow leaf beetle 1.7
the incubation penÍod depended on the neaning temperatu:re. At 14.3oc,
the íncubatíon peniod was 14 days, wheneas at 25.1oc it was only foun days. Gibson et aI (fSZS) found that the egg incubation peniod fon the
Colonado potato beetle was 14 to 17 days at a mean temperature of 15oC whereas it was five to 10 days at a mean temperatuï,e of 22oc.
2.!.3,4 Larval stage
Cniddle Gg22) and Vlalken (fgsO) pnovided the most detailed descr:iptions on the larval stage of the sunflowen beetre. cnid.dr e (ßzz) stated: ttrhe lanvae ane pean-shaped, the head being the nannow end.. They ane smooth above with numerous tr:ansverse nidges tenninating neat' the sides close to the spinacles ãnd bondened below by a pr.ominent, wninkled, Iatenal fold and a less conspicuous one beneath it. undenside flattish containing numenous fine, shont hains; anar extnemity pnolonged fonmlng a bifid pnocess which aids locomotion. Legs well dãveloped black at tips. coloun of head light bnown h'ith vrhite hains, body pale yellowish.tt Walken (rss0) stated: ttNewly hatched lanvae wene 1 to 3.5 mm long while matu::e lanvae wene I to 1-2 mn rong. The ranvae wene light gneen in co.Loun, the donsal su:r'face having narrow tnansvense light yellow stnipes on the anal mangín of each body segment to the latenal mangin; ventnal sunface da::k ye11ow; head capsule light br:own. The ana1 end of the lanva had a flat disc-like protnusion which adhered to sunfaces and assisted the ínsect in locomotion.r Ïlestdat (1974) descni.bed the sunfl-owen beetle ranvae as being dull
yel1ow-g::een, hump-backed and measu::Íng appr:oxinately 10 rnm when fu1ly grovJn.
Feeding behavíou:r of the lanval stage of the sunflowen beetle has been mentioned by most nesea::chers wor.king on this ch:rysomelid. The lanvae ane noctunnal feedens, nemaining hidd.en and inactive in bracts of the flowen bud and in the leaf axils dr::ning the day (l{estdal tg75; Rogens 7977). Larvae feed on the newly formed leaves in the terminal by chewing holes in the leaves (Cri¿¿te t922, Vlalken 1936). Bnisley
(rgzs) noted that the lanvae never destnoyed the bud, but ate onty the very young leaves as they unfolded, thus insu:ring a futune food suppry. westdal (tszs) stated that eanly danage by young lanvae may appears insignificant, but as the leaves gror^r they take on a shot-hoLe appearance. westdal (rgzs) funthen neponted that the plant may be completely deforiated if the lanvae are numerous (i.e. 25 on more pen plant ) .
Rogens (tSlZ ) neponted that the sunflowen beetle had four. l-anval- instans with head capsule measunements of 0.45 1 0.003, o.g0 1 o.ot+, 1.16 J 0.016 and 1.58 J 0.015 rnm, nespectivery. Fou:r lanval instans have also been neponted for Z. suturalis (pípen lgZS), Z. disnupta (eipen 1978), Z. tontuosa (Goeden and Ricken 1979)o the Color.ado potato beetle (Ginault and Rosenfeld 1907), the willow leaf beetre (Daviaurt
1941), and the milkweed teaf beetle (Eickwort 1,g7t).
Rogers (7977) ptrblished the only detaÍIed l-abonatony data on the du:cation of lanr¡al developrnent. He found that at 27 ! 2oc, lanva1 deveropment was conpleted in 1s.1 i 0.5 days. The dunation of each of the four larval instans was 4.5 t 0.1, 3.s t 0.1, 3.9 t 0.1 and 3.g t 0.2 d.ays, nespectively. lfalken (lggO) neponted that the lanva1 stage lasted appnoximately 16 days r:nden field conditions in Kansas. pipen
(fgZS) found that Z. suturaLis nequined. 15 to 18 days to complete 1ar:val development at 20 to 25oC. Pipen (1978) detennined that Z. disnupta 19 required 20.3 t 0.9 days to complete larval d.evel.opment when neane¿ at
24 ! 2oC in the labonatony. Goeden and Ricker (1929) found that Z. to::tuosa nequined 20 ! 3 (nange 13 to 22) days to complete developïnent at 27 t loCo of which I t 3 days (nange one to 11) was spent nesting on the leaf as a nonfeeding, fou:rth instan. Daviault (1941) for:nd that the du:ration of the lanval stage of the wirlow leaf beetre was 32 days at 16.goC and 18 days at 21.6oC.
In Manitoba, Cniddle (1-922) found sunflowen beetle lanvae on plants th:roughout the month of July with rnatune ranvae starting to
Pupate nean the end of July. Westdal (fgZS) stated that 1anvae can be found. in srnflowen fields fon about six weeks, but he did not mention specific dates. I{al-ken (1936) obsenved matune lanvae faIl to the gnound to pupate on JuIy 13 to 16 in Kansas in 1931-32.
2.1.3.5 Pnepupal and pupal stages
Cniddle (1'922) noted that upon completion of l-anva1. development, the rntune larva enter.ed the soil not fan fnom the plant on which it had developed. ttarken (tsgo) found that pupation took place in an eanthen chamber at a depth of 2.5 to 2.5 cm whire Rogens (tg77) reconded pupation at depths of 2 to s cm. No descniption of the pnepupal stage was found in the litenature while the only mention of a pupal descníption was by lfestdal (1975) who stated that the pupa r^ras yellowish and about the síze of the adult. pipen (197s, !g7g) obsenved z. sutu:ralis and Z. disnupta pupate in eanthen charnbe::s at depths of 2 to I and 5 to 10 cm, respectively. Gibson et al (rgzs) observed the colonado potato beetle pupatíng in eanthen chambens at a depth of 20 1 to 15 cm in the field. They obser"ved consid.erable vaniation in depth cornesponding to diffenent soil textu:res.
lfalken (1936) stated that the sunflower: beetle renained in the
eanthen chamben fon appnoximately 17 days and llestdal (192s) noted the
peníod to be appnoximately 10 to 14 days. The above peniod would
ínctude both the pnepupal and pupal stages. Rogens (tSlZ) found the
pnepupal peniod and pupal peniod to last 4.9 t 0.2 and 6.7 ! 0.2 dayso
respectively, when neared at 27 ! zoc. pipen (rgzs) reconded that the pnepupal and pupal stages of Z. sutunal-is lasted. seven to eight and six to nine days, nespectÍvely, when neaned. in the labonatony at 24 ! zoc.
He also noted that the tenenal adult nennined in the soíl fon two on
th¡ee days befone emenging. pipen (1979) noted the pnepupal and pupal stages of Z. disnupta lasted 6.9 t 0.6 and 7.9 ! 0.1 days, nespectively,
and the tenenal adult nemained undengnound fon one to two days when
neaned at 24 t 2oc. The total subtennanean peniod, ther.efone, was appnoxinately 15.6 to 16.6 days. Goeden and Ricken (tgzg) found that each of the pnepupal and Pupal stages of Z_. tontuosa lasted foun to five days when neaned at 27 t 1oC. Gibson et al (fSZS) found that the
pnepupal peniod of the Colonado potato beetle lasted thnee to five days and the pupal peniod seven to 15 days depending on temperature.
Daviault (rg4r) found that the average dunation of the pnepupal and.
pupal peniods fon the wilIow Leaf beetle was 6.5 and 7.5 days, nespectíveJ-y, fon a totat of 14 days. Again he noted that tempenatu:ne significantly affected the nate of development. Fon exampre, the total subtennanean period at 24.goc was only nine days wheneas at lz.aoc it was 24 days. 27 2.1.3.6 New-generatíon adult
Behaviour" of new-genenation adul-ts appears to vany according to
geognaphic lbcation. llalken (rggo), ir l(ansas, noted that upon emengence
the new-genenation adults irnrnediately began to feed, mate and 1ay eggs.
He, thenefo::e, concruded that thene'$rene two genenations of the sun- flowen beetle per year Ín l(ansas. In Manitoba, howeven, I{estdal (fgzs)
obsenved that new-genenation adults fed for" a shont pe::iod on the
uppermost leaves of the prant befone neentening the soil to pass the winten. Thus, l{estda]_ (1975) agneed r^rith Cniddle (7922) that the
sunflowen beetle had but one generation per yean in Manitoba. Rogens
Qslz) neaned the beetle in the rabonatony at 27 ! zoc and a 14:10 L:D photopeniod, and was abl-e to pnoduce a continuous-br:eeding population.
He detenmÍned that the tine nequined to eomplete one genenation was
47.7 ! 0.9 days (i.e. f::orn the emergence of a femare to the emergence
of its adult pr"ogeny). He, thenefone, speculated that thene was a
potential of three complete genenations pen yean in Texas, but because of low populations in his field monitoning plots he was unable to confir:m this. Mitchell et aI (1978) monÍto::ed various sunflowen pests
in Texas and found that there appeared to be onry one seasonal peak
(in June) fon the sunflowen beetle. pipen (1975, LgTg) found that Z.
sutunalis, in OhÍo, and Z. disnupta, in Texas, $rere bivoltine. Goeden and Ricken (1979) found that Z. tontuosa was univoltine in southenn Califonnia. The Colonado potato beetle is knov¡n to be univoltine in nonthenn areas and multivoltíne in southern aueas (Gír,ault and Rosenfeld 1907; Johnson and Ballinge:: 1916; Gibson g! al 1925). DeWilde (1962) 22 concluded that photopeniod was the majon factor: in diapause inductÍon
in the Colonado potato beetLe, with tempenatune and food qr:a1ity being secondany factons.
2.1.4 Sunfl-ower beetle eontr.ol necommendations
Upon emengenae, posthibenration adults move to seeded fields
whene they feed on seedlíng plants. Darnge may nesurt in delayed
matr'r::ity and seed losses of eight pencent even with mod.enate d.efolia- tion (Westdal et al- 1976). Cunnent necommendations ane that insectí-
cides shouLd be applied when populations average one adurt pen two on
thnee sunflowen plants (llestdal et a! 7976). A sample size of 100
plants examined at nandom has been suggested (Anonymous 1979b). Insecticides cu:rnently negistened fon contnol of sunflowen beetle adults
in canada incrude azinphos-methyl, canbofunan, endosulfan and methidathion (Anon]rmous 1979c). Toxaphene Ís the only ínsecticide registened fon use against the sunflowen beetle ín the United States (schutz 1978). lfestdal et aI (1976) stated that one insecticide application is usually adequate to obtain pnactícaI control of aduLts even though fields may be ne-invaded within a few days due to the short nesídual líf,e of the bunnently negistened insecticides. contnor of new-generation adults in the farl has not been necommended (Anonynrous 1e7eb).
Lanval damage by the sunflowen beetle is usually a mo¡e senious pnoblem than damage by posthÍbernation adults. Like the adults, lanvae ane defoliatons and a yield neduction of 30 percent has been neponted
(Vfestda1 et aI 1976). An economic thneshold value of 10 1anvae pen plant 23
has been suggested (Anon¡rmous 1979a, 1979b). A sarnple of 100 plants
examined in locations taken at random has been necommended when
assessing lanval- nurnbens (Anonymous 1979b). Insecticides negistened fon contnol of adults of thç sunflowen beetle ane also negistened fon
contnol of the lanva (Anon¡rmous fgZgc), Westdal et al (!976) suggested
that a single insecticide application aften all the eggs have hatched should destnoy all the lanvae on the plants. fnsecticides should not
be applied aften prants ane 60 cm high on aften heads begin to fonm (Anon5rmous 1979b0 1979c).
2.1,5 Natunal enemies of the sunflowen beetle
2.7.5.! Pnedatons
In neviewing the litenatune, few nefenences vrere found which mention pnedatons of the sunflower beetl_e (ta¡te Z).
Penillodes (peniltus) biocul_atus (F.) was noted feeding on sunfl-owen beetle larvae ín Albenta (Anon5rmous 1923), an obsenvation
arso made by Rogens (rsgo) in Texas. p. bioculatus is also a wetl-
known pnedator of colorado potato beetle eggs, lanvae and adul-ts (Tnouvelot 1931; Feytaud 1938; Hancount tgTt). Westdal (1925) mentioned a Pentatornid as being a pnedaton of sunflowen beetle lanvae in ManÍtoba, but no species designatÍon was gíven.
lÍestdal (1975) noted that Lebia atniventr.Íq Say fed on sunfLowen beetle lanvae in Manitoba. Lebia atniventnis has also been noted as a minon pnedaton fo the Color"ado potato beetle (Trouvelot 1931).
Anothen Lebia species, L. g:randis Hentz has been considened. an Table 2. Published lrecords of p::edatons of Zygqgnamma exclernationis attacked ---
COLEOPTERA CARABIDAE Lebia atniventris Say Lanva llestdal 1975
COCCINELTIDAE Coccinellíd sp. Egg, Lanva Westdal 1975
HEMÏPTERA PENTATOMTDAE Pentatomid sp. Lanva llestdal 1975 Penilliodes bioculatus (F. ) Lar:va, Adult Anonymous 1923, Rogens 1980
HYMENOPTERA ENCYRTIDAE Copidosona sp. La::va Rogens 1980
NEUROPTERA CHRYSOPTDAE Chnysopid sp. Egg, Larva Vlalker 1936, lfestdal 1975 Chrysopa carnea Stephens Lanva Rogens 1980
+t\) 25
impontant pnedaton of the Colonado potato beetle and much wonk was done in hopes of intnoducíng it to Fnance to contnol the potato beetle (Trouvel-ot 19.31; Feytaud 193S).
I{estdal (XgZS) noted sunflowen beetle eggs and l-anvae beíng attacked by coccinellids in Manitoba, however, no species designation
was given. Goeden and Ricken (1979) neponted Hippodamia convenge¡s Guenin (coleoptena:coccinelridae) feeding on eggs of z. tontuosa in Califonnia. T¡ouvelot (1931) also neponted coccineLlids as being pnedatons of the Colonado potato beetle.
Ì{a1ken (1936) rentioned that chnysopid lanvae wene obsenved. feeding on young sr¡r¡flowen beetle lanvae in ÌGnsas. ffestdar (197s)
arso obsenved chnysopid ranvae feeding on sunflowen beetle eggs and
lanvae. Rogens (fggO) found the ch¡ysopid, Chrysopa carnea Stephens,
feeding on sunflower beetle l_anvae ín Texas.
Rogens (fgao) also obsenved. CopÍdosoma sp. feedíng on sunfLower beetl-e lanvae in Texas
2.t.5.2 Parasites
Aneviewof the litenatwe indicated no necond.s of parasites of the sunflower beetle. Kelleher (1gOO) collected the sunflowen beetle
in a survey fon panasites Ín 1958. A singre specimen of Do:ryphor.ophaga
macella Reinhand (liptera:Tachinidae), which is lodged in the Canadian National Collecti.on in Ottawa, vras neaned fnom the sunflowen beetl-e.
Tn a review of the litenatu:re on panasites of the Tnibe
Donyphonini, thene are only two necords of panasites being reaned. from species of Zygogramma (Table 3). cole (1969) neported Adonyphonophaga Table 3. Published records of parasites ¡'eaned from beetLes of the Tribe Doryphorini (Chnvsomelídae: Chrysomelinae) in North Aneriea
Host Fani ed nefenences Callig¡epha spp. Adorlf,horophaga eberrans Tovmsend D:t Cole 1969 Callignapha rnultipunctata (Say) : Eupñõrocera crãrïõiffiïË-( üacquart ) D:t Coquillett 1897 (Kby ffiIFãpñã ;ñi.t¡j5u¡ cEr tã bisãbyana egg Erixestus v¡innemana Crawfortl H:pt Crawf-ord 1910; Daviault 19t+1 Catl+grEpha nultipunctata bigsbyana (Kby larr¡a Eeteonirs sp.-:- H:b Daviault 1941 Calli grapha rnultiprm ct ata bigsbyana (Kby adult EEpñarus canadensÍs Reinhard D:t Reinha¡rd 1945 Callísrapha multíÞunctata biesbvaná (Kby adult lfyiopharus dorsalis Coquillett D3t Daviault 1941 Callignapha scalarÍs (Iæc) egg Erixestus winnemana Crawfond H:Pt Crawford 1910 (say) @èe-'p[ã ffi egg ffiG'fiñemara Cnawford H: pt Mullins 1976; Wheeler and Hoebeke 19?9 Eã6'ïæ-cijlÍcõiiís ( Kby ) adul-t Tærnsend D:t Eick$¡ort 1977 ËTïã.j'..I'e eEõfïIE (¡Gt) adult rae Eickwort A:po Bake¡: and Eiekwo¡¡t 1975 FFffisffi'iTã-eata (say) larva, a¿lult send D:t " Briand 1957 Ctiñotarsa ffiffiæ (sat) larva s Reinhard D:t Kelleher 1960, 1966 Leptinotarsa decemlineata (Say) larva Aõrypñorae (Piley) D:t KelLeher 1960, 1966 Cprïñæ ãffiIïñFa'(sat) lanva nacella Reínhard D:t Kellehe¡r 1960, 1966 iãpffi'õtaGæerær) Larva ffiEãïis Reinhard D:t Reinhand 1935 ãsorryrrqq conj r{lãtã ( F.ogens ) alerrans To¡¡nsend D:t Cole 1969 Zy soE am'É EóFãÍóE-( rogãrs ) larva dorÌyphoiae (Rifey) D:t Gordon and Ricken 1979
rder A=/ìcani; D= ptera; H=Hynenoptera Family code: b=Bnaconidae¡ po=Podapolipidaei pt=Pter:omal!.dae., t=Tachinidae
q,N) 27
abbenans Townsend neaned from Z. conjuncta (Rogens). Othen hosts of A. abberans includ.e Celtig¡.apha spp. (Cole 1969) and the Colonado potato
beetle (Bníand 1957). Goeden and Ricken (fSZg) neared Doryphorophaga
donyPhonae from Z. tortuosa. c.w. Sabnosky (pens. comm.) of the UnÍted
states Natíonal Mu$eum in llashington, al-so has an ord necond. of
Donyphonophaga macerla being reaned fuom Zygognamma signatipennis (stgr)
ín Anizona. As índicated in Table 3, both D. doryphonae and D. macella
have arso been neaned fnom the colonado potato beetle (Keuehen 1960,
1966 ) .
ffisky,SysternaticEntorro1ogyLabonatony,USDAc/oU.S. National Museum NHB 168, Washíngton, D.C., 20560 28 2.2 Myiophanus sp., ê tachinid parasite of adults of the sunflowen beetle
Since the tachÍnid reared fnom adult sunflowe:: beetles du::ing
the cou:rse of this study is a new species withÍn the genus Myiophanus Bnauen and Bengenstamm, the following literatu.ne r:eview ,rt;- necessity deal with infonmatíon on the genus Myiophanus. A description of the new species by Dr"..D.M. Wood of the Biosystematics Institute, Ottawa, will be published elsewhene.
2.2.1 Taxonomíc status of the genus Myiophanus
The genus Myiopharus was fÍ::st pnoposed by Bnauen and Bengenstamm (tegg). sabnosky and. Annaud (1965) praced Myiophanus in
the Tnib,e BlondeliÍni, subfarnily Goníinae, Family TachinÍdae. Many
female membens of the Tnibe Blondeliini ane chanactenized by a shanply pointed ster:notheca used in pier:cing the integument of the host d.uring lanviposÍtion. Myiophanus species, howeven, have a rounded. knife-l_ike stennotheca presumably used to sepanate the elytna of the aduLt chnysomelids they panasitize (O.¡,t. llood pers. comm.).
Sabnosky and Annaud (fSOS) líst thnee Nonth Amenican species belonging to the genus Myiophanus, namely M. canadensis Reinhand, M. donsalis (coquillett), and M. secunis Reinhand. g. canad.ensis and M. secu:nís wene described by Reinha:r,d (1945), while M. dorsalis was oniginal- 1y descnibed by coquiJ.lett (1898) ín the genus Exorista. pankeniellus fLaviparpis smith of smith (1916) is synonymous with M. donsalis. ---.-ffi.E:Tooa, AgnÍcultune Canada Resear:ch Bnanch, Biosystematics Resear.ch InstÍtute, Ottawa, Ontanio, K1A 0C6 29 2.2.2 Geognaphic distrÍbution and host reconds
Reconds of the geognaphic distníbution of Myíophanus species
Índicate a fainly wide North Amenican distnibution. Myiophanus
canadensís has been collected fnom Quebec and Ontario (Reinhard 1945).
The type species fon M. donsalis was descnibed fnom pennsylvania
(Coquillett 1B9B) r+hi1e Sabnosky and Ar"naud (1965) tist the dístnibutíon as rdaho to ontanio and New yonk, south to califonnia,
Texas, rowa and New Jensey. M. secunís was d.escnibed from specimens collected in Texas (Reinhard 1945).
Annaud (fgZg) gave only two host-parasite ::ecords fon the
genus Myiophanus. The finst nefenence was to Reinhand (rg+s) who neared M. canadensis fnom the wilIow leaf beetle, calligr"apha
multipunctata bigsbyana (iOy), in Quebec and the second. neference to Daviault (rg+f) who neaned M. donsalis also fr.om the willow leaf beetle
in Quebec. rn neviewing the u.s. National Museum collection ín
Ìùashington, Sabr:osky (pens. comm.) found no host necor.ds fon Myiophanus.
2.2.3 Bionomics of Myiophar.us
The only published paper on the biology of a Myiophanus species was by Daviault (rg+r) on M. dor"saris neaned frorn the willow leaf beetre in Quebec. Daviault neaned only three species of parasites duning his work on the bionomÍcs of the wilrow reaf beetle, with Myiophanus donsalis being the only panasite neaned. fuom the adu1t. The othen species nea::ed we:re the egg panasite, Erixestus winnemana Cnawfond, and the lanval panasite, Meteonus sp. He classed M. donsalis along with 30
E. r¡innemana as being mone impontant than Meteorus sp. Daviaurt
concluded that M. dorsalis pnobably had only one genenation per yean on the wil-Low reaf beette in Quebec. He obsenved that M. dorsalis ovenwintered as a nraggot lnside ovenwintening adults of the willow leaf beetle. The ûÌaggots developed slowIy in the abd.omen of the hosts until they neached matunity the next spnÍng. Panasitization sta::ted in July shontly aften the emengence of new-genenation adults of the willow leaf beetle.
Daviault (rg+r) noted that, in the faII, panasitized wirlow
leaf beetres l-ooked like non-parasitized beetles, but in the sp::ing the
pa:rasitized beetles took on a danken shad.e and often had a dank spot on
the elytna. Th.ese panasitized adults did not feed and becarne sluggish
following a distention of the abdomen caused by the developing maggot.
Fínally, pa:rasítized adults bur"nowed in the soil_ to a shallow depth where the maggot killed the beetle. Daviault found that M. donsalis
pupated inside the nemnants of the adult beetle and finally emenged as
an adult thnough the postenion of the beetle. Daviault noted ttrat U. donsalís adults Lived an average of 7.5 (nange six to nine) days in captivity when fed sugar water.
2.2.4 rmpontance of Myiophar.us in negulatÍng host popurations
Again Daviault (1941) published the only infonmation negarding the influence of a Myiophanus species on a host population. He found that of 210 adult willow leaf beetles collected in 193s, 49 (2r.g pencent) vrere parasitized by M. donsalis. rn tggl, he found that 14 of 72 (t9.4 pencent) adul-ts collected wene parasitízed. He did not pnovide 31 the dates on v¡hich these coll-ections weue ¡nade. He concluded that the effect of M. donsalis on the willow leaf beetLe population in Quebec was significant. 32 2.3 Enixestus wilnemana cnawfond, a pteromalid panasíte of eggs of the stnflowen beetle
since this ís the fi::st necond of E. winnemane being nea::ed
fuom the sunflowen beetleo the following litenature neview will_ deal only with infor:netion on E. winnemana neaned. fuom other.reconded hosts.
2.3.1 Taxonomic status of Enixestus winnemana
The genus Enixestus was finst pnoposed by cnawford (1910) wittr
the type specíes fon the genus being Enixestus winnemana. To date
thene is still only one specíes in the genus. peck (feSf) placed E. winnemana ín the Tnibe Tnidymini, subfamiry ptenomalinae, Family Pter"omalidae.
2.3.2 Geognaphic distnibutÍon and host neconds
All- nefenences indÍcate E. winnemana to be a panasite of eggs
of Chnysomelidae with a fainly wide North Amenican dÍstribution. li the
oniginal descr"iption, Crawford (1910) mentioned that E. wirurenana was
neaned fnom the eggs of the willow leaf beetle in Manyland and fuom the eggs of the eln callignapha, Callignapha scalaris (Leconte), in vinginia. DaviauLt (1941) ín Quebec, also neaned E. winnemana fnom eggs of the wíIlow l-eaf beetle. Bnor.rn (1956), in Ontanio, neported neaning
E. winnerana fnom the eggs of anothen chnysomerid, chnysomela lineatopunctpfa (Fonsten). Mul-lins (1976) neponted neaning E. winnemana foon the eggs of callÍgnapha spinaeae (say) in vínginia. lfheelen and Hoebeke (1979) nepeated this tratten recond fon pennsylvania. g. winnemana appears to be the only egg pauasite nea¡ed fuom membens of the
Subfamily Chnysomelinae . 33
2.3.3 Bionomiçs of Er.ixestus winnemana
Adult males and females of E. winnemana look much alike and ane
about 1mm long (Cnawfond 1910). They ane d.eep pr.u,ple above, with a metallic blue-gneen abdomen and face, brown antennae and with the legs
and tips of the mandibles stnaw-colouned. (Cnawfond 1910; Daviault 1941). Mo::e details on the descníption wene given by cnawfond (1910).
Panasitized eggs appeaned símilan to non-pa:rasitized eggs
except that the5r wene dank orange instead of yerrow or pale onange (Daviau1t 1941). Panasitized eggs could also be distinguished since
the outlines of the developing wasp could be seen thnough the chor"ion
of the host egg (t'tutlins 1976). Daviautt (1941) mentioned that he obtained oviposíting females in the labonato::y by the second on third
week in June. Eggs panasitÍzed by these femal-es pnoduced adult E. winngmana within 11 to 18 days. Mullins (1g76) ::eponted that the life
eycle was only seven days in vinginia. when E. winnemana completed
deveropment, Ít chewed a nound hole nean one end of the egg in or.den to
exÍt (Daviault 1941). Both Daviault (1941) and Mullíns (1976) assumed.
that E. winnemSna had a numben of genenations per yean because of the
veny shont time nequined to comprete development. No nefenence was found for. the ovenwintening stage.
2.3.4 Impontance of Enixestus winnernana in r"egulating host populations
Daviault (fg+f) provided some data on the nate of panasitísm on the will-ow leaf beetle in Quebec. Du:ring the couse of his studyo he estimated the rate of egg panasitism by E. winnemana to be 63 pencent 34 in 1934, 26.5 pencent in 1935, and 54 pencent in 1936. Daviarrtt considened E. winnerana to be one of the two most impor.tant panasites of the wilIow leaf beetle. 35 2.4 Do::yphorophaqa macella Reinhand, a taehinid panasite of lanvae of the sr¡nflowen beetle
2.4.1 Taxonomic status of Donyphorophaga ¡nacel.Ia
The genus Donyphonoplaga lras suggested by Townsend (tgt2), who pnoposed DgTyphongphaga (l,y¿etta) doryphonae Rirey as the type species.
Reinhard (rggs) descnibed foun additionar species in the genus
Doryphonophaga, namely D. austnalisr 4. macella, !. sedula and D. patnita. Sabrosky and A¡-naud (1965), howeven, consid.ened D. patr.ita synonynþus with D. sedula and praced it in the genus Ador"yphonophaga.
They, thenefone, necognized only thnee species, D. austnalis, D. donyphonae and D. ma.cella in the genus Donyphorrrphaga. They placed the genus Donjrphonophaga in the Tnibe Brondeliini, subfamily Goniinae,
Farnily Tachinidae. It is intenesting to note that both Adonyphonophaga and Myiophanus wene also placed in the Tnibe Blond.eliinÍ.
2.4.2 Geognaphic distnibution and host neconds
The distnibutíon of Donyphonophaga species is fainly widespnead in Nonth Amenica. D. macelra was descníbed by ReÍnhand (1ga5) fnom specimens coLlected fnom Texas, Ohio and Michigan. Sabnosky and Annaud (1965) descnibed the distr"ibution of D. macella as Manitoba to
Massachusetts, south to Califonnia, Mexico and Flonída. Kel1ehen (1OOO,
1966) neaned D. macel]a fnom Colonado potato beetle lanvae in Manitoba.
In a neview of the litenature on the Tachinidae, A::naud (1978) listed the Colonado potato beetle as the only known host of D. macella. The nefenence he síted was that of Kerlehelr (1966) on work done in 36
Manitoba. D.M. llood (pens. conm.) neponted that thene ane in the canadian National coltection two specimens of D. macelra neaned in Manitoba fnom the aFpen poplan beetle, Goníoctena (phytodecta) (schaeffer) amer"icana (coreoptena : chnysomelidae : chnysomelinae), and a
single specirnen of D. macelra neaned in saskatchewan f::om the aspen leaf tien SciqphÍIa duplex (Walsingham) (Lepidoptena:Olethreutídae).
As stated ín section 2.1.5.2, c.l¡I. sabnosky (pens. comm.) of the
United States Natíonal Museum has a necord of D. macella neaned fnom
Zygognanrna signatipennis (st8r) in Anizona. D. macella, the::efone,
aPpeans specífic to membens of the chnysomelid Sr¡bfamily Chnysomelinae
with the exceptíon of the one specímen lrealred fuom the olethneutid, S. duplex. No doubt additíons to the host-panasite neconds fon Donyphonophaga wi1l come to light in the futune.
2.4.3 Bionomícs of Qonyphor"ophaga macella since this is the finst neco::d fon D. macella as a parasite of the sunflower beetle, the following literature nevÍew will deal with infonnation on D. macella neaned. fnom othen neconded hosts. Also,
since infonmation on D. nacella is limited, this neview will also deal
with data on D. donyphonae and D. aust::alis .
2.4.3.1 Ovenwintening and spning emengence
The overwintening stage of D. macella or any of the other
Donyphonophaga species has not been detenmined, although thene havp been speculations. CoLe (1951) in hís stuciy on the Iife histony of the
Colonado potato beetle in ManÍtoba suggested that D. doryphonae nay nigrate fnon the south each yean. Anothen possÍbility, suggested by
Kellehen (fg0o), was that D. donyphonae rrny ovelrwinten as a pupa in the
soil. He found no evidence to suppont that theony, howeven, beeause he
courd not detect diapause in D. dor.yphonae. Even in late season
coll-ections of host lanvaer g. donyphonae eithen emenged as an adult on
died in the pupanium due to unknown physiological causes. A second.
theony pnoposed by Kellehen (1960) was that D. donyphonae ovenwinte:red as a maggot in ovenwintening Colonado potato beetle adults. He based this theory on the fact that in díssections of pupae and adults of nel^Í-generatíon Colorado potato beetles he found finst-ínstan maggots which he pnesumed to be Donyphonophaga species. He speculated that, fon some lreason, rnaggots deposited in the host l-anvae failed to kill the host in the pnepupal stage and thus nemained do¡rnant thnough the pupal and adult stages of the host. He was unable, howeven, to near any pauasites fnom adults of the colonado potato beetre collected. eithen in the faIl on spning. Al-so, no parasites wene collected in energence cages set out in potato fields in the spnings of lgs8 and
1959. A thínd theony of Kelleher (fgOO) was that D. dor^yphonae had no dÍapause and must bneed continuously. This laten theony supponted the theory of Cole (1951). In his sunrnany, Ketlehen(tgOO), howeven, listed onry his second hypothesis which suggests that he pneferned that theony
Although thene is no published infonmation on the spning emengence of adults of Donyphonophaga thene ane some data on the finst seasonal obsenvation of par"asitized host lanvae. Fnanz (1957), ín 38 Ontanio, found the first nature colorado potato beetle lanvae panasitized with Do:rLphonophaga maggots on July 6. Kellehen (1960) found Donyphonophgga maggots ín the finst seasonal colrections of
mature (tuin¿- and for¡nth-instan) colonado potato beetle larvae taken in Manitoba fuom JuIy 6 to 10 in 1957 to 1959. However, Kel1ehen (1960)
appanently did not dÍssect host larvae in ea¡lien instans since he assumed that they wer¡e not attacked by Donyphonophaga sp.
2.4.3.2 Matíng, lanviposition and longevity
No nefenence was fourrd which descnibed mating behavioun by
Donyphonophgga sp.' non was there any mention of nating being obsenved. even in studíes where successful lanviposition Ín the Labonatony was (Feytaud achieved 1938; Ke1leher 1960). Kelleher (1960) for:nd a pnelanvipositÍon p.eniod of seven days on ress, ínclicating that successfi¡I mating must have taken place even though it r^ras not observed.
No nefenence was found descnibing the lanviposition behavioun of 9. macel-la, but thene were some descniptions fon D. dor.yphor.ae. Tov¡nsend (tgtz) descnibed the nepnoductÍve habit of g. don]4>honae as subcutaneous lanvÍpositÍon, that is, the female punctures the integument of the host with a eu:rved spine-like abdominar piencen, then injects a finst-instan maggot inside the body of the host by means of a closery associated but sepanate lanvipositon. Tnouvelot (fgSf), Bnwreteau (1SSZ), Feytaud (1938) and Kel1ehen (1960) a1I agneed !,ith Townsend's (tstz) obsenvation of panasitization by subcutaneous lanvÍposition and also gave a bnief account of the lanvíposition behavioun and the hostrs 39 reaction. These wonkens also attempted to l:ear D. donyphonae in the
labonatony, but only Feytaud (1997) was abre to near a comprete
genenation; howeven, these flies failed to pnod.uce progeny. Kellehen (rgoo) had difficulty Ín getting D. donyphonae to attack suitable hosts and often when attacks wene fhade, he found upon dissection that the hosts did not contain r¡raggots. He f inarly achieved successful panasítism when he neleased panasítes in a gneenhouse compantment and pnovided Ìnature color-ado potato beetl-e lanvae. Kellehen (1g60)
hypothesized that the abr:¡ldant light in the g:reenhouse $ras r:esponsible
fon the suceessfur panasite attacks, although he did not pr^ove the theony.
since most wonkens had difficulty gettÍng D. donyphonae to panasitize hosts in the labonatony, thene is little infonmation available on the nepnoductive potential of the panasite. rn
dissections of females of D. donyphonae, Townsenð. (tgt2) forurd about 150 white maggots ín a rine in a rong, srenden, coired ute::us.
Tnouvelot (1931) assumed that a Donyphonophaga femare woul_d attack col-onado potato beetle lanvae sevenar times a day. F.eytaud (1938) reconded up to nine colonado potato beetle lanvae being attacked by a síngIe fenale on one day. Kellehen (fgOO) gave no d.ata on the
lanvipositíon nate of Donyphonophaga sp. No neferences were found whích descnÍbed the dunatÍon of the lanvÍposition peniod. (1960) Kerreher" noted superpanasitism by Donyphonophaga sp. on colonado potato beetle lanvae, but in numerous reanÍigs only a single panasite emenged fnom each panasitized lar.vae. In dissections of field collected host lanvae, he usualry found only orie maggot pen host but
occasionally two on three maggots wene found in the same host. He
noted supenparaBitism most fuequently duning peniods or years when the incidence of panasitism was high. Kelleher (fgOO) neponted that in greenhouse tnials, thind- and founth-instan colonado potato beetle larvaè r¡rere sometimes killed by the nepeated attacks of the lanvi-
positing females, He neconded up to 24 fír.st-instan rìaggots in one host lanvae. He speculated that du::ing years of high panasite
incidence, some hosts may be killed by nepeated attacks by
Donyphonophaga fernales .
The only nefe::ence indicati.ng the longevity of adults of D.
rnacella was by Kellehen (1960). He neponted that six adults hetd ín a
cage and fed only sugan cubes lived up to 31 days wíth an average of 16
days. By contnast, 37 adults of D. donyphonae fed the same diet lived up to 56 days with an average of 13 days.
2.4.3.3 tanva
Kellehen (1960) found that Doryphorophaga sp. passed thnough
three lanval ÍnFtans. He stated that the instar"s could be sepanated,
based on the shape and size of the buccopharyngeal appa-natuso the latten beíng 0.12-0.18, 0.25-0.38 and 0.69-0.90 mn in tength for" the thr.ee instans, r"espectively.
Townsend (tStZ) descnibed maggots of D. donyphonae as: tr. . . having well-developed r"ov¡s of micnoseopic spines, of which the finst th::ee nows and the last row encincle the body, the intenmediate six nows being on the ventnal sur"face and about half encincling the body.r'
Bnu¡reteau (1937) sketched the lanva of D. donyphor"ae. 41 No nefenence was found which dealt with the deveropment of maggots of D. ma.cej_Ig: but Kellehen (1960) pnesented infonmation on D. donlPhonae. In dissections of Colorado potato beetle lanvae, freshly panasitized in the labonatory, he found that the mean body length of finst-instan maggots was 0.54 rrn. in dissections of fiel-d. panasitized lanvae that wene stirl- feeding on potato foliage, he found only finst-
instan naggots and they had a mean body length of 1.1g mm. He, thenefone, concluded that maggots of ¿. donyphonae nemaÍned. in the finst instan vlith little development takíng place while the host l-anvae were stirl feeding. However, once the host lanvae conpleted deverop_ ment and entened the soil- to fonm a pupaÌ chamben, the maggots quickly completed development. Kel1ehen (1960) found that the maggot forrned a nespinatony funnel adjacent to, but not attached to the abdominaL spinacles of the host. The maggot of D. donypho::ae kill_ed the host while the host yns still- in the pnepupal stage. Death was usuarly neconded about two days pnion to the compretion of this lanval stage. Once the host was killed, it quickly turned a dark colou:n and stanted to decay. rn pnepanation fon pupation, the mature ¡naggot rnade two openings thnough the integument of the host. One openíng r^'as located on the vent¡al sunface of the host between the foneregs while the second was in the posterion donsum of the abdomen. At that time the fully developed naggot compretely fílled the hostrs abdomen and. measrured 4.6-9.0 mm in length. Kellehen (tgoo) estimated that the total below-g:r'ound peniod of naggot deveropment, fon D. donyphor"ae, Íras about six days. 42 2.4 .3.4 Pupa
Again there l^Ierâe no nefenences dealing with pupa.l deveJ_opment of macgll9r (1960) l' but Kellehen pnovided data on thÍs subject fon D. donyphonae. He found that the tachinid usually pupated wíthin the remrìants of the host and was oniented with its antenion spinacles thnough the anteníon hol-e in the hostrs integrment lrith the postenion
spinacres thnough the postenÍon hole. He found that the pupal peniod lasted about eight days when neaned at room tempenatune.
2.4.3.5 New-genenation adult
Kellehen (rg0o) pnovided data on the totaL developmental peniod
of D. macelIa. rn neaning studies, he found that, on avenage, ad.ults of D. rnacella emerged two days laten than dÍd adults of the unpanasitized host. By companison, ad.ults of ¿. don)¡phonae emerged an average of 6.3 days laten than did adults of the host. Developrnent of parasite the thnough the last two instans is obviously napid aften the host entens the soil since the resulting panasite adults emenge within a few days of unpanasitized host adults.
Kellehen (1960, 1966) provided data on the s]rnchnony of the new-gener?ation aduLts of Donyphonophaga with Ianval populatiorr of the colorado potato beetle. He concluded. that the par.asite was in poon s5mch::ony since ner^r-generation adults of the panasite wene emenging in late .Iu1y to eanly August when the lanval population of the host was napidly deelíning. He suggested that the panasites would be more effectíve in aneas whene thene h'as stíll a high populatÍon of host 43 lanvae at the time the new-generatÍon panasites emenged.o on whene the Colonado potato beetle had two generations per year.
Kell-eher. (fS6O; 1966) concluded that D. doryphonae had two generations pen yean on one generation of the Colonado potato beetle in Manitoba. Panasites of the ove::wlnfening population stanted to attack
matrule host Larvae in early July, wÍth the nesulting progeny emerging
du-ning the I-ast week of Ju1y. These new-genenation panasites began
attackÍng the decl-ining lanval host population in the finst week of
August. The second genenation parasite pnogeny emenged in níd to r-ate
August. The fate of these second. genenation pa.::asítes r^ras not ]cnown.
2.4 .4 Impontance of Doryphor:ophaga nncella in negulatirrg host poputrations
Thene llere no nefenences found in the litenatu:le which dealt dinectly with the incidence of panasitism of D. macelLa on a host
population. Kelleher (fSOO) mentioned that ¡. qggr¿l" nepnesented 10.9
pencent of the Dor"yphorophaga species he neaned and identified from Colonado potato beetle lanvae in Manitoba. He neponted íncidence of parasitísm ín the field or 25 to B0 pencent fon Dolyphorophaga species duning yeans the 1957 to 1g5g. Thenefone, the nate of panasitism by D. macelLa would have been appnoximately 2.7_g.7 pencent.
rncidence of panasitism by D. donyphonae has been noted to vary between negÍons, between yealrs, and between weeks within years. Bniand (1936) neponted incidence of panasitÍsm in the Colonado potato beetLe of 40 pencent ln chatham, ontanio, 1s to 50 pencent in Brand.on, Manitoba, 44 and 17 percent in Fnedenicton, New BnunswÍck fon the yea:r 1935. As mentioned pnevíousJyn Kellehen (tgOO; 1966) found 25 to g0 pencent
parasitism by Dor.ypþor.ophaga specÍes in Manitoba fnom 1952 to 1959. Hancount (7971) neconded incidence of parasitism of 0.S to 12.5 (mean 4.5) Pencent whil-e conducting life tabl-e studies on the Colorado potato beetle in the Ottawa ar:ea fnom 1961 to t967. Latheef and Hancount
(tsz+) fornd tB.2 to 28.8 pencent of the Colonado potato beetle lanvae collected f,nom tomato foliage anound the Ottawa a:rea fnom 196g to j.971 l¡ene parasitized by g. donyphonae.
Hancou:rt (7971) found that D. doryphonae was invensely density- dependent in its actÍon on Colonado potato beetles feeding on potato, that is, the panasite did not nespond. to annual- changes in host density.
The absolute numbens of the pa::asíte vanÍed little fnom one yean to the next. The:refone, in yeans of low host density, D. donyphonae kirred a high pnopontion of the availabre host popuJ-ation and in years of high host density, i.t kiri-ed a lowen pnopontÍon. Kel_lehen (rgoo; 1966) and
Hancou:rt (tSZt) concluded that al though the panasite could cause heavy montarity, it did not signifícantly negulate the population of the col-onado potato beetle feeding on potato. Hancount (1971) speculated that D. don]æhonae wourd have played a none inpontant nore when the Colonado potato beetLe was at endemic population levels in its original habitat, but with the introduction of the potato plant to Nonth AmenÍca, and its intensive monocul-tune, the parasite was unable to cope with incneased host popul-ations. The beetle, therefone, escaped neguration and achieved pest status. 45 Latheef and Har"court (1974) found that D. donyphonae was density-dependent Ín íts actÍon on Col-onado potato beetles feeding on
tonnto. lhey concruded that the parasite acted as a stablizing agent and did nespond to fluctuations of the host population at the densities
studied. They nationalized this appanent change in the natune of the densíty response by statíng that the action of a mortality factor such
as D. donyphonag is unlikely to nemain constant throughout the whole
nange of host population density. They found that the population leve1
of colo::ado potato beetre l-anvae on tomato was substantially lowen than potato on because thene was high Lanval montality on the fonmen due to the rinsuitability of the tomato prant as a food. source. Thenefore, at
these l-owen host densíties, fluctuations in sunvival wene damped by direct response of the par:asite. 46 2.5 The use of ther'rnal unit accumulations in Ínsect contnol
The influence of tempenatur"e in detenmining spr:ing emergence and subsequent deveropment of insect populations has been werl establ-ished. Thenefone, when descnibing the bionomics of an insect, the use of a time scale that is temperature-dependent has obvious
advantages ovell a tÍme scale based on calendan dates. Fon example, the
occunlrence of vanious events in the life cycle of the insect can be
more accurately pnedicted using a tempenature-d::iven time scale since vaniations in loçal and seasonal r¿eathen conditions can be taken into
account. This tempeqature-dependent time scale is often descnÍbed by
an accumulation of thenmal units (tU) as pnoposed by Eckenrode and chapman (1972). The terms degnee-days and heat units have arso been
used interchangeabry wíth the tenm the'rnal uníts (Arnord 1g60;
Bakenville and. Enin 1969; AJ-len 1976). All ane based. on the pnineipal
of carcurating the daÍly number of uníts of heat above a given base on
thneshold tempenature (To) and summing this value with the accumulated
numben of urrits of heat detenmined fon the d.ays pnevious. The
incidence of vanious biological events can, thenefone, be descnibed and pnedLcted based on the numben of accumulated rurs.
The concept of TU accumulations has been successfuLJ-y adapted
fon studies invorving a numben of insect species. Fon example, TUrs have been used to pnedict the spníng emergence of the chenny fnuit f1y (.lubb and cox 1974. Ali Niazee 1976, tgTg), the pink bollwonm (Sevachenian et aI 1977b), the apple maggot fly (Reissig s!al 1979), and the cotton fleahoppen (Stenling and Hartstack tgTg). Ives (1973) 47 proposed a TU accumul-ation appnoach to predict outbreaks of the for"est
tent catenpíllan, while Sevacher.ian et aI (tg7la) used TU accumulatíons
to time insecticide applications fon Lygus bugs on safflower. Data on
accumulated Tuts.ane impontant inpute into insect control models
cu::nently unden deyelopment (haynes'et al L97J; croft et ar 1976; Riedl et 1976; al Gutiennez s! ul 1977., sevachenian et ar 1977a, b; Tummala and Halmes 1977). Litsíngen and Apple (tszs) detenmined the TU nequínements of the alfal-fa weevil so that mone timely sunveys fon the pest could be conducted. A numbe:: of wonkens have used accumulated TUrs to describe the bionomics of panasite-host populations (Campbet] et aI 1974; Gage and Ha¡rnes 1975; campbell and MaclGuen 1977; Eklund and simpson 1977; obryski and Tauben 1978; and Johnson et ar 1929). As TU nequinements are detenmined fon more species of Ínsects, flìore pnactical uses wil-l be developed fon this impontant concept.
2.5.7 Procedunes fon calcul_ating thenmal units
As stated by Ives (tSlS), and Sevachenian et a! (Lg77a), thene
ane,thnee impor-tant factor:s that must be known befone TUrs can be
calculated and sumned. Finstl-yr an appnopniate th:reshold temper:atune
fo:r the onganÍsms must be detenmined., secondly, a suitable rnethod fon
carculating thenmar unÍts based on maximum daily and. minimum -*j temper"atures must be seLected, and thínd.ly, the nelevant per.iod. fon accumulating the TUrs must be chosen to correspond with the life cycre of the onganism.under study. Each of these points will be dealt with sepanately. 4B 2.5.1.! Methods of estimating the thneshold tempenatune The baqe tempenatune or lowen thneshold temperature (Tor,o) is
considened to be that temperatul:e below which the nate of development
of insects and othen poikilothenmíc or:ganísms wour-d be zeno. A ToLo would have to be detenmined fo:: each species unden study. Annold (rgsg)
suggests two methods fon estimating tol,o; the x-intercept method and
the least vaniability on lowest coefficient of vaníation method. The x-ínter:cept method of Annord (rgsg) is based on the obsenvation that the ::ate of developrnent of or"ganisms such as insects has a linea:: r:esponse to tempenatu::e, at least in the middl-e ranges of
suitable temperatunes. The nate of development woul-d be expnessed as the necipnocal of the dur.atÍon of devel-opment ín d.ays (r/¿ays). This ::ate of development is often multiplied by 100 to obtain the per.cent development pen day. A linear equation is detenmined with y = rate of development and x = mean tempenatune. An estimate of the ToLO is
determined by solving the X = 0 (i.e. the X-intencept). This method
has been used to detenmine the ToLO of a numben of insects, examples of
which can be found in Litsingen and. Apple (fSZg), Eklund and Simpson (7977), chmiel and vlilson (tg7ga), Johnson et ar (1979), Reissig et al- (1979), stenring and Hartstack (rgzs), BanÍ and Lange (rseo), and lfeinbeng and Lange (fgeO).
A second method by Ar"nold (fgSg) to estimate ToLO was the
method'of least vaniability or lowest coefficient of vaniability (CV) wheneby a nange of theoretical ToLOs was tr'íed and TU accumulations
calculated for a given peniod. By nepeating this pnocedure fon vanious 49 locatíons and times, the TU r.equinements fon a given stage can be
calculated oven the nange of theonetical_ ToLOs. Means, standar.d. deviations, and coeffícíents of vaniation are calculated fon each ToLo tested. The rol,o that prod,uces the lowest c.v. is declaned. to be the best fit, and ís thus chosen as the'T.LO to be used in futune TU carculations. Exampres of this method nay be found in Litsinger and App1e (1973), and Chmiel and Wilson (fgZg¡). The lowest C.V. method is especially suited fon insects that ane difficurt to near ín the labonatory, since field data can be utilÍzed to estimate the ToLo. Recently, thene has been inter.est in estimating an upper fo (foUp) as werl as a l0wer: To (ToLo) fon incorponation into a TU carculatíon fonmura. An e: 2.5.1.2 Methods fon calculating TUfs Most crimatological stations report oniy daily maximum (MAX) and minÍmum (MTN) temPeratures, thus nethods of calculating TUrs based on daily MAX and MrN ane most usefur. some of the nethods pnoposed and used fon insect population studÍes will be considened. Lindsey and. Newman (1956) appr:oximated the shape of the daily tenPerature cycte using a tnÍangulation pnocedur.e. Having a known ToLo, they prrcposed (hou:r]y) that TUts could be estimated using daÍ1y MAX and MrN' (1973) rves modified the Lindsey-Newman method slightly so as to carculate TUrs (daily) instead of TUrs (hoi:nr-y), that is, the daily TUts ane t/24th the numben of hounly TUts. The carcul-atíons pnesented 50 below ane fnom lves (1973) and would coven the following thnee situations: f. if MTN and MAX a:re gneaten than ToLO, then MrN MAX TU's (daily) J ror,c) = 2tuu - 2. if MIN and MAX ane less.than ToLO, then TUrs (daÍly) = O 3. if MIN < ToLO < t"fAX, then ru's (daily) = ffif Ives (1979), and Mattson and Enikson (197g) utitized the Lindsey_ Newrnan method in calculating TUrs fon the fonest tent catenpillan. rves ( 1973) stated that he prefenned the method because it was simple and the calculations wene easily prognanmed into desk-top calculatons. Annold (fgoo) pr:oposed a rnethod based on the sine cur"ve that would srightry impnove the TU estimation fon sÍtuation thnee (ut¡¡ < < ToLO MAx) and pnovid.ed a connection table fon this situation. Hís fonmurae fon situatíons one and two wene the same as those fon the Lindsey-Newman method. Arnordrs method has been fuequently used to cal-culate TUts fon insect population studies (Jubb and Cox 1g74; Ali Niazee 7976, !979; Dowel-l and Fitzpatnick 1979; Johnson et al 1979; Reissig et ql 1979). Additional modifications fon calculating TUts wene presented in laten papens. BaskenviLle and Emin (fgOg) modifíed Ar,¡roldrs sine culrve method to accorn¡nodate a Toup and ToLo. Gage and Haynes (1gzs) and Riedl et al. (1976) utilized the Baskenville-Emin method. Abnamí (tg72) modified the Lindsey-Newman method to accommodate a Toup a¡rd roto. 51 A1len (1976) proposed a funthe:: modification of Arnoldrs sine curve method by altowing fon a TouP and ToLO and by computing TUrs one-half day at a time which allowed fon possÍble differ.ences in the two MrN anound a MAX. Sevache::ian et al (tglla) púoposed a funthen modification to the Lindsey-Newman method. They calculated TUts one-half day at a time and allowed for a TouP and ToLO. They pnefenned. this method oven the sine cu¡ve methods because the cornputations wene nelatively simple and díd not nequíne access to a computen. chmiel and Ìfilson (1979a0 b) funthen modified sevachenianrs method to calculate daÍry TUrs in oc instead of hounly TUrs in oF. Fon the thr"ee situations sited pneviouslYr the fonrnulae accor"ding to the Chmiel-Wilson method would be: t. if MIN and MAX greaten than ToLO, then TU's (daily) fo:: ttrat half of the day would be *(|4+II9 - roLO = 0.2s (¡rex + MïN - 2rolo) 2. if MIN and MAX less than ToLO, the TUrs (daily) for" that hal-f of the day would be = 0 3. íf MIN < ToLO < MX, then TUrs (daity) fon that half of the day would be T.LO)2\ o.2s (uex "ß44åztã(mfÏÍN)-/=W - - ror.o¡z Two calaulations wourd, therefore, be nequired fon each d.ay to carculate the totar number of TUrs (daily) accumurated on that day. rf the ToUP is known, then the above listed fonmulae ane used sr:bstituting TouP fon ToLO and TUrs carculated. The net TUrs are calculated by subtracting TUts using Toup from TUrs usíng ToLO. chmÍel and !Íilson 52 (1979b) found that fon the tine peniod they studíed, theÍn npdified sevachenian method b¡as accurate within fou:: pencent com¡-raned to Arnordf s sine cunve method. 2.5.7.3 Appnopniate peniod fon ealcr:l-atíon of TU accumulations The third facton that has to be considened before TUrs ane calculated and accumuLated is the most appnopriate stanting date. Fon example, if an e.stinrate of the accumulated TUfs before spning emengence is requined, the staf'ting date should be before the finst insects would be expected to emerge, but after a date that obviousJ-y would not affect the timing of the emengence. Often such dates have to be chosen somewhat anbitnanily. once a stantÍng date is chosen, TUts ane carculated fon each day and accumulated. The occunrence of vanious biological events ean, thenefone, be connelated to accumulated rurs which wene calculated with an appnopniate ToLO 53 2.6 The comrnencial sunflowen - histony and pr"esent status in Canada The cornmencial sunfl-ower is one of a few pr"esent-day food plants to have been onigÍnarly domesticated in pnehisto::ic times in what eventually became the U.S.A. (Heisen 197g). Archeological evidence reveal-s that the sunflower was pant of the cultune of Nonth Amenican Indians fon 30 centunies or mone (Heisen j.g55). The fndians used the sunflowen not only fon food but also for" medicinal and cenemonial_ punposes. Mone details on the pnehístonic use of sunflowen in Nonth Amenican may be found in Heísen (1951.). The sunflowell I^Ias finst intnoduced into Eu::ope via Mexico to spaÍn dr:::íng the eanly 16th centuny (zukovsky in putt 1978). By the end of the 17th century' the sunflowen had been intr.od.uced to Belgíum, Holland, Switzenland, Ge::many and England (putt 1g7g). By the end of the l8th centu:ryn sunflowe::s began to be gro!{n on a commencial scale in RussÍa. The Holy onthodox chunch of Russia may have inadventently caused this intenest in sunflowers since the chu:rch had stnict negulations pnohibiting many oil foods, but they omitted specific mention of sunfrower:. consequentry, sunflowe:: oil became a popular food (Heiser 1955). By the later pant of the 19th century, Russian vanieties of sunfrowens wene ne-intnoduced to Nonth Amenica. one of the majon ways the sr.rnflowen I^Ias bnought in was via Mennonite immignants who settled Marritoba ín and saskatchewan (putt 197g). Much of the genetic sour:ce matenial for eanly selections on sunflowens fon Oanadian pnoductíon, in fact, came fnom the gardens of such inmignants (putt 1g7B). 54 Sunflowens wene finst grown on a commer.cial scale ín Canada in 1943 in nesponse to a request by the Govennment of canada fon the pnoduction of mone oíls during I'IorId War. II. The initial cnops ',¡ere gnown in Saskatchewan and Albenta, but shor"tÌy thereaften pnoduction shifted almost entinely to the Red Riven valley region of south-centnal putt (1979) Manitoba. cnedits this shift to the fact that Mennonite farmens in the region had had experience with sunfl-owens in smarr- ganden plots and quÍckly adapted the cnop to a field scale. The rong g::owing season and the expenÍence fanme¡.s had with othen now cl.ops, helped establish sunfrowen as an impontant cnop in the negÍon. Tr.ro types of sr¡rflowen are grovrn. one type, carled oirseed sunfl-ower, pnoduces small, well filledr::ound seed with a thin hul_l which is used fon the extnaction of edibre oil. The second type, usually called non-oilseed or" confectioneny sunflowen, pr:oduces lange long seed with a thíck, heavy hulr used fon dinect human consumption (putt 1978). oirseed sunflowen has consÍstentry been the mor.e important type gnown in Manitoba. A numben of oílseed sunflowen curtivans have been g::own in Manitoba since the finst intnoduction of the cnop. Eanly bneeding wonk Ín Canada, usíng Russian r¡anieties of sunflowens b::ought over. r^rith the Mennonite immignants, nesulted in the nelease of the cultivars rMennonitet, tsunniser, and the hybnÍd cultivans rAdvancer, rAdventl and rAdminalt (Putt 1978). Stanting in 1964, RussÍan cultivans such as rPenedovikt ?l(¡asnodanetsr and. wene intnod.uced to canada. These cuLtivans had a much highen oil content than the canadian cultivans, 55 thus making the latten obsolete (putt 1g7g). Anothen nnjon development in the late 1960ts was the discover"y of cytoplasmic male stenility in sunflor¿ens followed closely by the identificatíon of fentility nestoníng genes. Hybrid seed courd, thenefone, be pnoduced efficientry and cheaply. Many such'hybnids are cu::rently being developed. They yield an avenage of 25 pencent mor:e than the Russian cul-tiva:rs, yet stiLl maintain a high oil content (Fick 197g). such developments have spanked incneased acneages in both canad.a and the U.S.A. oven the past five yeans (Cobia 1979). Fnom 1949 to 19g0, an average of 30 ,717 hectarles hrere sor^m to sunflowens ín Manitoba (Anonymous 1980). ThÍs ::epnesented 95 to gg pencent of the Canadian pnoduction. rn Manitoba, duning the peniod 1926 to 1gg0, an avenage of 871000 hectanes wene sown to sunfrowen with a high of 1s4r000 hectanes being ::ecorded ín 1979. The estimated total- vaLue of the 197g Manitoba sunflower crop v{as $S0r417r000 (Anon]rmous 1gB0). 56 3. MATERIAL AND METHODS The matenials and methods used in this wor"k will be descnibed hene only in genenal. Details nelatíng to indivÍdual tr"ials wíIl be pnesented later unden appnopniate sectÍons of the Resul_ts and Discussion. vanious types of cages were used dr.æing this study, and will also be described in appnopniate sections (Fígr:res 3a to 3d). 3.1 Pnocedunes fon pnoviding and naintaining stock eolonies 3.1.1 The sunflowen beetle - stock colony New-gener:ation adults wene collected fnom sunflowen plants in commencial fields in south-centnal Manitoba in eanly Septemben and kept in nefnigenated storage until needed. Fon storage, the beetles we:re sealed in 750 mI plastic containens contaíning about 500 g of moistened stenilized soÍI. The containens with the beetles were stoned. at 9 t 1oc fon two weeks and subsequently held at 2 ! loc until the beetres wene need.ed. Beetles could be kept at 2oc fon up to one year. To break diapause of stoned ovenwintening adults, containens of stoned adults wene t:lansfenned to a holdíng cabinet at g t 1oC fon two weeks. Beetles l.Iene then nemoved fnom the soil and placed in covened. glass cuLtune dishes which contained noistened silica sand and. snal-l excised sunflowen leaves. The reaves wer"e obtained from seedling sunflowens cv. Per"edovik gnown in a gr:eenhouse. Appnoxinately 10-25 beetles wene placed ín each dish. The dishes r"rere then put in a growth cabinet at 28 ! zoc, and 16L:8D. Diapause was consid,ered terminated when beetles emenged fnom the sand and started to feed on the excised 57 Figu::e 3. Cages used duning studies on the bionomics of the sunflower beetle, Zygogna¡nma exclamationis (A) Plastic cylínden cage (B) ALuminum screen cage (C) Scneened emergence cage (D) Nylon screen cage 58 leaves. This tneatment usually nequined thnee to six days. Dellilde (1957) fcnackingt used a simil-an díapause tneatment fon the Colonado potato beetle. Adults of the sunflowen beetle wene tnansfenned to caged penedovik. 'ônce sunflowen seedlings cv. diapause was tenminated the sex of the beetles was detenmined and they wene caged on potted sunflowens in eithen of two tlipes of cages. The finst type (Fígune Ba) !üas a crean plastic cylinden 10 cm x 25 cm l¡íth s4-gauge nylon cloth oven ventilation holes at the sides and top. The second type (FÍgure 3b) was a cylínden, 15 cm x 35 cmo of aluminum screen attached to galvanized ínon ning 7.5 cm deep. Each cage was placed oven one or two potted sunfrower'(s) in the two- to eight-leaf stage. usr:aIr_y tr,Io females and two males wene plaeed in each cage. This constituted a stock colony which was rnaintained in a gnowth cabinet at 23 + goc, 16L:BD, and 70 per.,cent RH. Beetres wene transfenned to fnesh prants twíce pen week. Eggs wene eithen nemoved fnom the plants and used fon vanious incubation and parasite studÍes, on wene l-eft on the plant and allowed to hatch. Lar"vae fnom the eggs in the stock colony wene placed singry or in g::oups of up to five on a singre'ncaged, potted sunfrower: in the two- to eight-Ieaf stage and held in a g::eenhouse at 25 I soc and 18L:6D. Cages wene not nequined because of the sedentany habit of the Ia::vae. Fnesh plants wene pnovided as :required and lanvae were nemoved as nequined. vlhen the rarval stage was alnx¡st complete, plastic cylinder cages wene placed oven the plants and the matune Lanvae were 59 allowed to pupate in the soír beneath the plant. upon emerlgence, new-generation adults wouLd feed fon a short time and then neenter the soil to hibennate. A nondiapausing colony was obtained by rear^íng the sunflowen beetle at a 15L:9D photopeniod anð, 22 t toc, 70 percent RH ( Section 4 .1 .9 .5 ) . 3.1.2 Myiophanus sp. - stock colony The tachiníd panasite, MyÍoÞhanus sp., was neaned fnom ovenwintening adults of the sunflowen beetle. New-genenation beetles collected and stoned and then subjected to the diapause-bneaking pnocedur"e. Active beetles were nemoved and used in stock col-onies. Beetles which did not emenge fnom the sand. wene moved to a contno1led- tempenatu::e cabínet at 22 t goC and were examined unden a low_powen binoculan micnoscope fon evidence of panasite development. A dank anea visíble thnough the integument on the ventno-latenal aspect of the head indicated that a nespinatony funnel of Myiophanus sp. had been fonmed. such host adults wene placed in 12 ml vials stoppened wíth cotton batting. The vials wene labelled and placed insíde screen-covened 7 cm x 1d cm plastic containens and netunned to the g::owth cabinet. The beetles in the vials were e> Newly-emerged adults of Myiopharus sp. $¡er:e neleased. fnon the vials into each of sevenal lange cages in a gneenhouse. The cages, .60 descnÍbed by Allen and Askew (1970), wene of wood. frame constr:uctÍon 0.6 m x 0.6 m x 0.6 m, covened with nylon screen and with a glass cover:ed plywood.floon; access was thnough a sleeve opening. The cages wene located dínectly unden a bank of fluonescent lights at 1gL:6D in a gneenhouse at 25 t soc. The parasites wene pnovided a diet, proposed by Allen and Askew (rgzo), fon adults of the onion maggot, Hyremya antiqua (Meigen), whicþ consísted. of 5 g sugar, 10 ml evaponated milko and 35 ml water and was soaked Ínto cotton-wool pads in a 9.5 cm petni dish. A second petni. dish containing a cotton-wool pad soaked. wÍth a solution of 10 g sugar in 35 mI of waten was also pnovided. rn additíon, yeast hydnolysate spninkr-ed on paper towers, fold.ed longitudínally, and insented ín 125 nl Enlenmeyen flasks filled with waten, senved as a funthen source of nutnients. Each container in each cage was changed tr^ro to thnee times pen week. 3.1.3 Enixsstus winnemana - stock colony Adults of Enixestus winnemana were reared fuom sunflowen beetre eggs eollected fuom sunflowen plants in commer:cial sunfrowen fierds in south-ceritnal Manitoba. The plants wene bnought into the labonatony and. the eggs gently teased off the leaves and stems with a dissecting needle. The eggs, in gr"oups of 10 to 200, were then pJ-aced in vials, ::anging in size fnorn 12 to 50 mI, stoppered with cotton- batting. The víal-s wene placed honizontalry on a metal tnay and held in place with plasticine. The eggs vrere kept at 2s ! locr 16L:gD, and 70 pencent RH. Sunflowen beetle larvae which emenged fr.om unpanasitized eggs wene nemoved. daÍly. Newly-emenged adurts of E. winnemana were 61 llemoved by means of a smal-I manr:al aspir:aton and placed fresh 30 to 50 ml vials stoppened with cotton-batting. Appncximately five to 20 panasítes wene placed in each vial. Liquid honey was pnovided in each vÍar as a food source. The vial was positioned honizontalry on the tnay in a mannen such that the honei was on the uppen inside s¡rface of the vÍal. Newry-laid srnflower beetle eggs r{ere pnovided fon the panasites by insenting sma1l sections of stems of sunflowen seedlings. Fnesh eggs vrene intnoduced eveny 48 houns with appnoximatery 10 to 50 eggs being exposed each time. 3.1;4 Donyphonophaga macella - stock colony AduLts of DonyphonoPhaga macella wene ueaued. fnom sunflowen beetle larvae collected fr.om sunflowen plants in commencial sunflowe:r fields in south-centnal Marritoba. Fourth-instan 1anvae wene coL.l-ected fnon plants, with tweezers, and placed Ín 250 nl candboard. cantons. The larvae $¡ene then placed in 7 cm x 10 cm plastic contaínens half fi]-led with noistened, pne-sifted sand (U.S. no. 14 scneen). Excised sr:nflowen leaves wene added to all-ow the lanvae to complete feeding befone entening the sand to pupate. The containen was covered with a scneened l-id and a filten papen to keep the moisture in the containen. Usually 20 larvae were placed ín each containen. The field-collected lanvae wene r?eared in a contnolled envinonrnent cabinet at 22 1 aoc, 1BL:60, and 70 pencent RH. containens were checked everly second. d.ay, and leaves neplaced as nequined. Nine to 14 days after the d.ate of collection, D. macel-la and sunflower beetle pupae wene washed fnon the sand with tap waten, using a u.s. No. 14 scneen. rndividual panasite 62 PuPanÍa were put into 12 rnl glass vials stoppened with cotton-batting and placed into fresh 7 cm x 10 cm plastic containens wíth a scneen l_id. The containens with the viars wene put back into the cabinet and examined daily fon emer:gence of adult tachinids. Newly-emenged adurts of D. macella wene s.exed with the aíd of a row-pollen dissectÍng mícnoscope; the presence of a ster:notheca Índicated a female. Adurts of 9. macella wene neleased fnom the neaning vials Ínto large cages ín a gneenhouse. The cages (O.O m x 0.6 m x 0.6 n), near"íng conditions (25 * SoC, 1gL:6D) and diet (Rtten and Askew 1970) wene identical to those fon MyÍophanus sp. (SectÍon g.1.2). Fifty to 200 adul-ts were kept in each cage. sunflowen beetre ranvae neaned in the rabonatony (section 3.1.1) wene placed in cages with D. macella to pnoduce the next genenation. Fon this pur:pose, 10 to 25 la::vae wel:e exposed for one to two houns and then placed in plastic cylindelr cages (Figu::e 3a) oven potted sunfl-owens and neplaced in the contnolled, enví::onment cabinet. Near the completion of the lanvar stage, the host ranvae were placed in plastic containens with moíst sand and excised sunflowen leaves. ì4ater:ials and pnocedu::es fnom this point until emengence of panasites were as pneviously descnibed. 63 3.2 Rate of development studÍes on rate of development wene conducted. with the sunflower beetle, and the panasites E. winnemana and D. macel]a, in the labonator"y at vanious constant tenperatures. Connnon pnocedu:res to estimate the lowe:: thneshold tenper€itune (ToLO) and thenmal r:nit (tU) nequinements for. the vanious life stages ane given bel-ow. ToLo was estimated by the x-intencept method of Arr¡old (1gs9) (section 2.5.1.1); that is, nate of development (y) was negnessed. on tempenature (X) and the X-inter.cept (toLO) of the nesulting equatíon (Y = a + ¡x) was detenmined by sorvíng fon y = 0. The theonetical thenmal unit nequinement (Theor,. TUrs) fon á given life stage was calculated f:rom the rate of devel-opment - ternper.atune regression equation whene: Theon. TUf" = # Obsenved thenmal unit neguinements (O¡s. TUrs) we::e calculated using the following fonmula: Obs. TU's = (Ro - ToLo) (D) whene Ro = neaníng tempenature ToLO = Iowen thnãshotd tempenatune calculated. by the X-inte::cept method D = dunalion (in days) of the life stage nea::ed. at Ro Examples on the carculation of ToLO, Theon, TUrs and obs. TUrs ane shown in Section 4.1.5.3. Field studíes wene conducted with caged and uncaged sunflowen beetles to detenmine the nate of development of vanious 1ife stages and. compared to that of labor.atory nesults. The ToLO estimated in neaning studies at constant tempenatures in the rabonatory was used in 64 calculating the accumulated TUts in the field. Field accumulated TUrs were caLculated using the ChmieL and Wílson (tgZga, b) modification of sevachenianst (tgzza) method (section 2.s.r.2). This nethod. was chosen because it was accurater yet neratively simple and did not nequi:re access to a computer. Maximum and ñinimum daily temperatunes from the closest reponting weathen statÍon wene used in calcurating TU accumulations in the fÍerd.. The stanting d.ate chosen fon TU accumulations was Apnil 1 fon each season, unless othe::wÍse indicated. 65 3.3 hocedunes fon detenmining incidence of panasitÍsm of the sunflowen beetle 3.3.1 Detenmination of panasitism by Myiophanus sp. Incidence of panasitístn of the sunflower: beetle by Myiophanus sp. lras deterrnined by two methods. The finst nethod was to dissect field-collected adults of the sunflowen beetle and. examine the bo_dy, ínside and out, for tachÍnid ¡naggots. Maggots of Myiopharus sp. Ì¡ene identified by the shape and size of the mouth-hooks (Section 4.2.2.1). This method was veny tedious and. time consurning. The second method was to near the panasites fuom overwintening adults of the sunflower beetle collected ín the field and maintained on potted. sunflower seedlÍngs in an aluminum scneen cage in a controlled envÍ¡onnent cabinet at 23 ! 2oc, 18L:6D, and.70 pencent RH. rnitialry, 20 beetres wene placed in each cage and fnesh plants pr"ovided twice a week. As beetles died, they wene praced in !2 mr vials stoppened with cotton-batting and examined daily for" evídence of panasite development. 3.3.2 Detennination of pa::asÍtism by Enixestus winnemana Incidence of panasitism of sunflowen beetle eggs by å. winnemana was detenmined only by labonatony neanings sÍnce dissection of eggs fon evÍdence of panasite d.everopment was not practical. Pnocedures fon deterrnining the incidence of panasitism of field_ collected eggs wene the same as those outlined in section 3.1.3 fon stanting a labonatony cultune of E. winnemana. 66 3.3.3 Detenmination of panasitism by Doryphonophaga macella rncÍdence of panasítism of sunflowen beetle lar:vae by g. macella was detenmined by both labonatony reaníng and by examination of pnesenved Ia¡vae. Fou:rth-instan host ìarvae wetae collected fnom the field and r"eaned in the labonatony acconding to pnoced.unes outlined in Section 3.1.4 for" stanting a labonatony eolony. Field collections of lanvae pnesenved in 70 pencent alcohol $rene assessed. fon panasitism by D' macelta in the following IIEnnêr. Finst, pneserved host lanvae fi:om a pa:rticulan sample were sorted into fou:r g::oups acconding to instar on the basis of head capsule size (Section 4.1.6.3) and gnoups placed in separate vÍals. Each viaL was then filLed with a 10 peneent solution of potassíum hydr.oxide (XOH) and held at noom tempenatune fon six to 10 houns fon the finst-, second.- and thind-ínstans and 10 to 19 houns for: fourth-ínstans. At the end of thís períod the body of the host was pantially dissolved, but chitinous stnuctur^es r^rere intact. The lanvae e¡ere removed fnom the KoH sorution, bniefly bl_otted on papen towelÍng and then placed on a microscope slide. A second slide was placed. over the lanvae and pressure gently applÍed so that the body was spnead. between the micr"oscope slÍdes. The slÍde pnepanation r^ras then viewed thnough a binoculan microscope at 20x powen. The dank-bnown to black mouth-hooks of the maggots of the panasÍte wene neadily visible among nemnants the of the host body. rd.entification of the maggots was detenmined by the size and shape of the mouth-hooks (section 4.4.1.3.1). This method was nelativery napid since up to 10 finst- on second_, five thind-' on tlro founth-instan sunflowen beetle lanvae could be examined at a time on one slide pnepa::ation. 67 3.4 Field sampling plots t97S to 1977 Foun sites vrene serected in comme::cial sunflowen fierds in south-centnal Manitoba oven the peniod 197s to tg7? inclusive, to follow the devel-opment of the life stages of uncaged sunflowen beetres and thei:: natu::al enemies in the fíe1d. one site was serected at ste. .lean in 1975' one at Letellien in 1g76 and one each at ste. Jean and Lowe Fanm in 7977. on Tuesday and FnÍday of each week, obsenvations wene made on the appea'ance and habits of vanious rífe stages of the sunfLower beetle and counts made on the numben of adurts, eggs and. larvae pen pnepupar plant. and pupar stages r^rere not sampted. The adults and eggs coqnted on each date were left on the plants, but arl lanvae examined duning the count welre r:emoved with hand tweezens an. pnesenved in 70 pereent alcohol. Measu::ements of head capsules were laten done to detenmine the instan dÍstríbution (section 4.1.6.3). Diffenent plants were examined on successive sampling dates because the lanval count was destnuctive. Beetles in the subplots $rere, thenefone, assumed to be nepnesentative of the popuration in the su:rnounding field on the samplÍng date. Results were neponted on a pen plant basÍs and on a TU accumulation time scale. The thneshold tempenatu::e (ToLO) selected to g.4oC calcuLate the TUrs was (Section 4.1.6.4.2). The TU accumulation method used was the chmiel and llilson modification of the sevachenian (sectlon method 2.s.r.z). The maximum and minfunum daily ain tempenatunes needed to carcurate the TUrs wene obtained fnom the I{eathen statíon at Monnis, I',fanitoba. The Monnis station was chosen because it was the station closest to the foun sampring sÍtes. 6B Reconds of the panasíte species and incidence of panasitism wene taken fon each population monítoning p10t. rncidence of panasitism by D. macella on the lanvar stage of the sunflower beetle was detenmined by examination of pnesenved specimens using a slÍde prepanation pnocedune (Section 3.3.g). panasitism incid.ence was al-so detenmined in laboratory neaning of sunflowen beetl-e lanvae collected from aneas adjacent to the monitoning plots (SectÍon 3.0.g). fncidence panasitisrn of by E. wínnemana on sunflowen beetle eggs and MyÍophanus sp. on sunflowen beetle adurts was also detenmined fon the 1g76 and 1977 sampling plots by laboratony neaning of egg an¿ adult collections made adjacent to the plots (SectÍons 3.g.1 and 3.g.2). Reconds on the numben and species of pnedatons present on each sampling date at each sampling plot wene also mad.e 3.4.1 Ste. Jean, 19Zs In 1975, the site was in a field of sunflowens, cv. l(rasnodanets, on the farrn of Mn. G. Fontaine (Iand location:13_3_1E) of ste. Jean, Manítoba. The fieLd had been sown May 13 and the popuration sampling plot staked on June 13. The Ínitiar plant stand. was appnoximately 4.5 plants pen meten of r^ow. The anea seÌected was appnoximately 100 meters fnom the edge of the field. and. consisted of 30 adjacent rows, each 27.4 m long with a 0.6 m bet¡+¡een-row spacing fon a total anea of 0.05 hectanes. Rows wene dÍvided into thnee equal subplots desígnated as Range one, two and thnee. Thene wene thus g0 sr:bplots, each 9.14 n Iong. 0n each sampling date, thnee subplots wene sampled, one subpl0t being taken at nand,orn fro¡n each nange. New 69 subpl0ts wene selected on successive sampling dates. sampling commenced June 13 and tenminated JvLy 22 because on Jury 23 the prot was inadventently subjected to dnift f¡om an aenial application of insecticide meant to contnol sunflowen beetle lanvae in the su:mound.ing fÍeld. TU accumur-ations fon the plot wene cal_cu-l_ated on the basÍs of data fnom Monnis the lleathen station which was appnoximately 16 km f::om the sampling plot. 3.4 .2 Letellien, 1926 rn 1976, the site selected was a fierd of surfrowelrs, cv. Knasnodanets' on the fanm of Mr". L.D. Barnabe (Riven Lot 14g) of Letellien, Manitoba. The field was solm appnoximatery May 15 and the staked ¿r site on June The plant stand was appnoxinately 3.5 sunflowens pen meter of row. The plot selected was appnoximateLy 100 meters fuom edge the of the field and. consÍsted of 30 adjacent nor"rs, each 36.6 m long with a 0.6 m between-r.ow spaeíng. Rows wene dÍvíded into foun equal subprots (Ranges), each s,bprot beÍng 9.14 m 1ong. on each sampling date two sr:bplots wene selected and sampled, one subprot being sel-ected from each of Ranges one and thnee on Tuesd,ays and one subplot from each of Ranges two and four: on Fnidays. New subplots wene selected on successive sampling dates. sanpling commenced. June 4 and tenminated septemben !7. The Monnis Ïleathen station was approximatel_y 19 km fnom the sampling pIot. 3.4.3 Ste. Jean, tg77 rn 1977, two populatÍon monitoring plots wene set up, the finst being in a fíerd of sunfrolle's, cv. sundak, on the fa:rm of 70 I"h". L. Hanblin (niven Lot 257) of Ste. ,Jean, Manitoba. The fiel_d was solid seeded du:ring mid to late Apnil and the sampling plot established on May 25. Because the field was solid seeded, a modified sampling plan was designed. The southenn edge of the field was manked off at S-rn intenvals fon a distance of 100 m. The sampling anea was thus divided into 20 sections. on each sampling date two sections were designated at nand.om, and a pnedetenmined sampling site 10, 20r 30 on 40 paces fnon the southern edge of the field was selected withín each of the two sections. At each rocation the finst 50 plants encountened wene sampled. The plants examined wene manked so that they would not be ne-sampled. sampling commenced May 25 and tenmínated August 5. TUrs wene calculated on the basis of data fnom the Monnis I,leathen station which $¡as applloximately B km fnom the plot. 3.4.4 Lowe Fanm, ITTT The second site sampred in rg77 was in a fierd of sunflowens, cvr l(:nasnodarets, on the fann of Mr". F. And.enson (to-s-tI{) of Lowe Fanm, Manitoba. Thís field had been sown dur.ing the second week of May, and the sampling.prot was set up on June 3. plant "t.r.á *u" approximately fíve sunflowens per meten of now. Since the field had been sown in nows, the plot design used was identical to that of the plot at Letellien, in 1976 (Section g.4.2), that Ís, 30 adjaeent rows, each 36.6 m long divided into fou:: Ranges to make a totar of r2o sttbplots each 9.14 m long. on each sarnpling date two subpJ_ots wene selected and sampred. New subplots $¡ene selected on successive 7! sampling dates. Sampling commenced June 3 and tenminated August 23. The Monnis l{eathen Station was appuoxinately 10 km fuom the population monitoning plot at Lowe Fanm. 72 4. RESULTS AND D]SCUSSTON 4.1 Biono¡nics of the sunflowen beetle in },lanitoba 4.1.1 Overwintening soíl sampling, fier-d obsenvations, and. cage studies were conducted to detenmÍne the over:wintening stage, the ovenwinter.ing site, and nepnoductive conditÍon of the sunflowen beetle. A tnial was also set up to detenmine the effect of snow coven on the sunvÍvar of ovenwintening beetles . 4.1.1,! Ovenwintering stage and site cage studies wene set up in and anound fields in which sunflower"s had grown been the pnevious yean, hereafter^ nefer.ned to as vorunteen fierds, to dete'rnÍne ovenwintening sites. In the finst study on overry,¡inter.íng sites (fiet¿ 1), emengence cages wene set up on May 14, tg74, in a field (11_Z_51{) owned by Mn. sandulak of canman, Manitoba. The cages wene galvanized metal cones 35 cm in diameten, topped wíth a glass corlecting jan; two circur-ar opposÍng side ventso 10 cm in diameter, covened with 54 mesh sararr screen wene pnovided fon ventílation. The cages wene íd.entical_ to those used by Kellehen (1960). Twenty-seven cages wene placed nandomly in the centen of a volunteen sunflowen field and 1g in a summe::fallowed mangÍn. The cages wene checked and. cleaned of beetles peniodicalry until June 3. A second study to detenmÍne ovenwintening sites (rier¿ 2) 'ms set up on May 2, 1976, in a volunteen sunflowen field (2_g_1W) ovrned by 73 ¡'tr'. A. Heínních of Rosenfeld, Manitoba. rn thís study, conicar cages with a hexagonal metar base, 46 cm in diameten, and scneened sídes topped with a netal collecting can (Figune 3c) we::e used to check emengence of sunfl0wen beetles. Twenty-nine cages we:e placed within a volunteer" sunflowen field and !2 Ln a gnassed mangin adjacent to a sheltenbelt. Cages wene checked and cleaned twice a week untíl the terrnination of the study on June g. fn the 1974 study, thnee sr¡rfl-owen beetles wene collected in t]ne 27 cages placed within the field, while no beetles r.rere collected Ín the 19 cages set up in the summenfallowed nangin (fa¡fe 4). The finst beetre was colrected fnom the cages on May 31, foun days later than beetles wene finst obsenved. in volunteer fieLds dunÍng the spr:ing of 1974 (Section 4.I.2.1). In the L976 study, 11 sunflowen beetles were collected in the 29 emengence cages wÍthin the vorunteen fietd,, wheneas none was collected in cages placed in the gnassed. anea. These studies indicate that the sunflowen beetle overwintens in the soil- within fields whene sunflowens were gllolrn. These nesults ane supponted by the obsenvation that pnehibennation adults wene not noted to dÍspense (SectÍon 4.I.g.2). The sunflowen beetle, thenefone, likely overwintens in the fierd in which it developed as a lanva To determine the ovenwÍntening stage and. ovenr¡inteníng site of the sunflowen beetle, soil exeavations were made in thnee voluntee¡. sur¡flowen fields duning the eanry spning of 1924 and 1975, and in one field containing matu¡e sunfrowens in the farl_ of !g7s. Arl fields 74 Table 4. Numben of adurts of the sunfrowen beetre, Zygognamma exclamationis, collected in emengence cageGE=Eõ-- ïõcaTlãfE-;outh-centnar r,fanitoba, 1924 and 1926 e location Date Field 13 May í-974 17, 0 0 l[ay 1974 27, 0 0 May 31, !974 0 2 .Iune 3 , 1974 0 t Field 2a l(ay 2, !976 0 0 May 7, 1976 0 0 May 10, !9V6 0 0 May 13, 1976 0 0 May 18, 1976 0 l(ay 0 21, 1976 0 t May 1976 25, 0 0 May 1976 28, 0 5 June 1976 1, 0 5 June 4, 1976 0 June 0 B, !976 0 0 , 19 emengence cages-posïI one a suÍlff¡enta mangin on May 14, 1974. ln fietd 2, t2 emengence cages posítioned Ín a gnassed margin on Apr.iL 30, 1976. =?7 29 enengence cages positioned withÍn a vor-unteer sunfrowe:r field"\d at Fields 1 and 2, nespectively. sFietd 1 Sandulak fanm, 4Field = laná locatiãn 11-7-5W, Canman. 2 = Heinnick fanrn, land rocation 2-3-1Ír, Rosenfeld. 75 vrene located within the sunflowen gnowing negíon of south_centnal Manitoba. Samplíng sites within each field wene located at nand.om. At each site, the soil was nemoved in fíve cm layens over a sunface a::ea of eÍthen 0.42 on 0.84 m2, to a depth of up to 60 cm. The soil was passed thnough two sieves, 2.s and 5.6 mesh pen cm2, respectivery, to collect any beetres pnesent. specimens found were prese::ved. in 70 pencent alcohol or an aqueous solution of chJ.onal hydnate, formaldehyde and acetic acid (Wgaven and Thomas 1956) and. Iaten dissected to determine the nepnoductive condition of ovenwÍntening females ( Section 4 .7 .1.2) . Exeavations in volunteer sunflowen fields nevealed that most beetles over:wj.ntened within the top 15 cm of soil, although one beetle was found at the 2s-90 cm depth (ra¡te s). Fonty-four percent of the beetles collected wene fnom the 0-5 cm depth. 0n1y adults of the sunflowen beet.Le we:re collected fuom soil_ samples taken in fields in south-central- Manitoba ín the spning of each of 1975 and 1976 (ta¡te s). This ag:rees with raboratony and fierd obsenvations that neÌ^r_genenation ad.urts collected late in the fal1 fed fon a shont peniod then r"eadiry ovenwintened in field cages on in nefrígenated stonage. The lanval 0n pupal stage was not suspected. to be the ovenwintering stage in I'fanitoba since l_anvae collected thncughout the season continued development and showed no evidence of diapause even when held at nelatively low tempenatures (section 4.1.7.2). No:r was the egg stage suspected to be an ove::wi.ntening stage since eggs wene not obsenved in the field aften míd_.Iuty (Section 4.1.4.6). These 76 Table 5 Nunben of sunflowe:r beetles, Zygogr.amma e xclamatÍonis - collected r at diffenent depths in soil at ïoun excavation sites in southenn Manitoba mple sunface area Numben collected at soil depth (cm) Fie1d2 Excavatíon date (mz ) t May 8, 7974 0. 84 01200000 7 May 8, 1974 0. 84 341- t May 14, 7974 0. 84 000001 t NIay 77, 1974 0.84 3030 2 May 28, 1974 0. 84 !1 4600 3 May 15, 1975 0.42 0000000_ 3 May 15, t97S 0.42 0000000_ 4 Sept. 16, 1975 0.84 00 ronly Its zField t = Canman, Sandulak fanm, land locatÍon 11_7_5Í1. Field 2 = Monden, Casey fa::m, land l-ocation 7_3_5Vf. FieId 3 = Rosebank, Thomson fanm, J_and location 30_4_5V1. 4 Field = Rosenfeld, Heinnick far:rn, land l_ocation 2_0_11,1 77 results agree with observations of llestdal and Barnett (fSSS), and with studies on othen membens of the TnÍbe Doryphonini (Gibson et al_ 1925; Daviault t94t; Eickwont t97I; pipen 1978). Wat-ken (1936) noted that in l(ansas sunf,lowen the beetre ovenwÍnt_ened in the pupal stage, howeven, thene was no evidence in this stud.y to indicate that the beetre ovenwintened a_s a pupa. ïn the farl 0f 7976' a cage study was initiated to supplement infonmation the on the depth in soil at which the sunflower" beetle ovenwíntens. On Septembe:: B, tg76, two cages wene set up in a s'nflowen fierd (rand rocation 30-4-sr^¡) owned. by Mn. G. Thompson of Rosebank, Manitoba, and anothen cage was set up in a srnall sunflowen plot on the gnounds of the Agnicultu¡e canada Reseanch station, wÍnnipeg, Manitoba. The soirs at both locations wene high in clay content whích is common fon the Red Riven varley ar:ea. The cages used wene simil_an to those descnÍbed by Nícholls (1970). They measu:red 122 cm hígh x 91.4 cm x 91.4 cm and wene constnucted of 32-mesh saran screen wÍth a 5 cm alumínum stnip attached to the bottom edge (Figune 3d). Each cage covened a sunface anea of 0.g4 m2. The cages wene placed so that each covened. tr^ro or3 thnee lange sunflowen plants. one hundned pnehibennation adul-ts collected fnom plants in a sunfl-owen field at ste. Jean, Manitoba, on septemben 7, 1976, $¡ere praeed inside each of the thnee cages. The beetles fed on the encrosed plants fon a shont time, then bunrowed ínto the soil. The soil was nemoved and sifted in 5 cm layens to a depth of 15 cm, on octoben B, 1976, at Rpsebank and on 0ctober 19, 1976, at WÍnnipeg. 78 cf 300 beetles placed in the ovenwintening cages, 294 (gg.o pencent) welre recovened following excavation of the top 15 cm of soi1. of the 294 necovened, (82.1 256 pencent) were fncm the 0-5 cm rayen, 36 (rr.s pencent) fnom the 5-10 cm laye:r, and one (0.3 pencent) fnom the 10-15 cm layen (Tab1e 6). rt should be noted, howeven, that the soil r'lEts ver^y compact below the 10 cm depth at both sites and that excavation past the 15 cm depth was not possible. The natr¡re of the soil at both sites may have affected. the overwintening depth. The effect of vanious soil t¡pes on overwintening depth shour-d be evaluated in futu¡e studies. Mail- and Gibson (1933) noted that the depth of hibennation of the coronado potato beetle varied dependíng on the texture of the soiI, and that the beetle wourd not penetnate the handpan. 4.7.7-2 Reproductive condítion of ovenwintening females The repnoductÍve status of overwintening fernales of the sunflowen beetle was determined by dissectíon and, sectioníng of thnee gnoups of beetles. The finst gnoup was made up of pr:ehibernation females collected fuom the field, the second gnoup r^ras ove¡wintening females taken fnom nefnigenated stonage and the thind goup was taken dÍnectly from ovenwintening sites in the field. Most specimens wene fixed in Bouínrs aqueous picr"ofonmor, dehydnated in ethanol, cleaned in xylene, enbedded in panaplast (mp 56-57oC), 10 "ectioned at ¡rm, and stained with Eh::lichrs hematoxylin and eosin. rn addition, some ovanies wene fixed in l(annovskyrs fixative (l(annovsky 1965) containing two to thnee percent glutenaldehyde and one pencent panafonmald.ehyde in 0.1 m cacodylate buffen pH at 7.4, washed in four changes of 0.1 m 79 Table 6. Number of overwintening adurts of the sunfr_owen beetle, ZyFggo"ryg, exclamationis, necovened. f::om soil in cages at Rosebank and Winnlpeg, Manitoba, Octoben 1976 botl_ depth (cm). Sunfacecì...^3- - - 0-5 5-10 locationl 10-15 Total- -cage #1 Rosebank-cage #2 00833730I wignlegs;casg 97 #1_ _0_ 100 Total o 2-- zsT --5--37 --s---o---1-- zgl % of total 0 0.7 85.4 7.7 10.9 1.0 1100 0.3 100 sunflowen l-e a ts pl each cage Septe Each cage covered a soí1 surface anea of 0.84 m2. eUnable to sift soil past the 15 cm depth due to soil compaetion. 80 cacodylate buffen, dehyd:rated in ethanol, cleaned in acetone, embedded Ín Analdite-Epon mixture (Anderson and Ellís 1965), sectioned at 2 Um, ar¡d stained with one percent toLuidÍne blue zeno Ín a one pencent borax solution on with two pencent azu¡e Ir Ín a one pencent bonax solution. ovanies wer:e classified to thein stage of dever_opment acconding to a system pnoposed fon the sunfl0wen beetle by Genben et aI (rgzg). They pnoposed two pnevitellOgenic stages and foun vitellogenic stages distinguíshabre by the size of the ultimate oocyte (Appendix 1). spennnthecae were also extnacted fi:om the specimens and e> The finst group of females examined were collected during the month August of ín the years tg7g, 1974 and 1975, to detenmine thre condition of the ovanies of new-genenation beetres pnion to hibennation. A total of 26 new-genenatÍon females wene coll-ected from commencial sunfl0wer fields and the stage of ovanian devel0pment d.etennined. 41L 46 p::ehibennation females cotlected had ovaries classified as Pnevitellogenesis Stage I (Table 7), that is, oocyEes T.rere not distinguÍshable in whore rþr:r¡ts, but one on two smarl ooc5rtes couLd be seen in histological sections of some ovaníores. Thene üras no evídence of spenmatozoa in the spenmathecae. These p::ehibennation adults wene, thenefone, sexuarly immatu'e. These nesultsr wene supponted by the fierd obsenvation that new-genenation adults wene neven noted nating nor laying eggs pnion to hibernation (section 4.1.g.1). Table Date 7, of collection, numben of females and. oocyte devel0pment wintening females of in pnehibennation and over- the sunflower. beetle, . Zygog::amma excl_amationis, tgTg_!g77 Date of Number- col-lection of fernles August 17, 79734 20 (0)2 1003( 0 0 aa ) 0 0 0 August 19 ) 1-9744 5 (o) 0 1oo (o) 0 0 August 23, 1975 4 (0) 0 0 0 2t 1oo (o) U 0 0 0 0 Septemben3, tg765 6(O) 0 1OO,(O) 0 O 0 s May19,ts769 s(o) o 1oo(o) o o Ì'ay 2t, 1e76þ 1 (o) o 1oo (o) o o õ o o o 2Number:s in parenthesis nefen to the ie::centág"-;;-f"Ë1Ë 1fr; had copulated. largest ultimate oocvte ":il:T:iå;r:i.tiÏã1::.:::"e was classified as being in the panticulan stage killed, and pnesenved on the same date. -ÞÏolledi9:11.:a:d, rn refnigenated bHibennating storage fon ten weeks then killed and pnesenved. beetJ-es sifted fiom soit, kírted po"""r"ved "rra on the same date. Þ@ 82 The second gnoup of beetles consisted of a sampre of síx overwintening females that were in nefnigenated stonage fon labonatony cultuning pul?poses (Section 3.1.1). These beetles had been collected at Letellien, Manitoba on septenber: 3, tg76, then plaeed in nefnígenated stonage fon 10 weeks (two weeks at fO t toC, six weeks at 2 ! !oC, followed by two weeks at 10 1 foC). The beetles were then taken dinectly f;nom stonage and assessments mad.e on ovanian development as descníbed above The ovar"ies of all- six females taken fnom nefnigerated storage wene classified as pnevitellogenesis Stage II (Tabte 7), that is, oocytes wene distinguishable in whote mounts of the ova::ies, and the ultimate oocytes were 0.4 rnm rong. Also, in examining the spenmathecae, thene was no evidence of mating. These beetres, thenefone, had shown sright ovanian development Ín compar:ison to new-gener.ation adurts collected and pnesenved in August, but they wer.e stÍ11 sexually immatune. The thÍr"d group compnised sÍx femar-es corlected duníng soil sanpling of ovenwintening site at Rosenfeld, Manitoba on May 19 and 23, 1976 These beetres ' wene examined fon stage of ovanian development and fon evidence of mating. The ovaníes of alr síx fenares co*ected dinectly fuom ovenwintening sites were classified. as pnevitellogenÍc stage ïr (ta¡te 7), which is the sarne classification as deter.mined. fon femal-es taken fnom nefnigenated stonage. All e: Ïn September of 1976' an expeníment was initiated to detenmine the effect of snow cover on ove::wintening sunvival, the stant of posthiSernation emengence und.er caged conditions in the fierd, emergence nate of males vs. fernales, and the state of ovanian development of newry-ernenged posthiSennation females. only the first point pnesented will be in thÍs section while the othens will be discrrssed, Ín sections 4.1.2.!, 4.1 .2.3, and 4.1.g.1, nespectívery. On September 15. !976, 50 pnehibennation adults collected fuom a sunflowen field at Rosenfeld the previous day wene put into each of 20 conical metal emergence cages (4.f.1.1) positioned in a foun by fíve gnid on a 3 m spacing in a summer-falrowed pJ-ot at the Agnicultune canada Resea::ch station, ffinnipeg, Manitoba. The cages wene modifÍed plugging by the emergence hole in the glass cor-lecting jan, thus pneventing beetles from being tnapped in the collecting jar. The beetl-es wene arlowed to enter the soíL beneath the eages as ín ovenwintening. on octoben 1g, !976, the cages were removed and the 20 sítes rnnked with 1.25 m metar poles. on the nronning of Januany 6, 1977 the snoür (appnoxÍmatery coven 10 to 15 cm) ïras re¡noved fron ever.y altennate site (i.e. 10 sÍtes whích contained 10 x 50 = 500 beetLes) and the snow on the nemaÍning 10 sites was undisturbed. on the night of Januar"y 6, the minimum tempenature was -g2oc and the avenage daily tempenatune fon the week of .Ianuary 6 to 12 was -2goc. snow coven was not removed at any othen time. on Apr"Ír 1g, tg77, scneened, emengence 84 cages (rigpt'" 3c.), wene placed oven the 20 ovenwíntening sÍtes. since the scneened cages had a rangen diameten than the metal cages (46 cn vs. 35 cn) eaeh site was furly cove::ed. The cages wene checked dairy until June 20 and the nu¡nben of sunfrowen beetles and panasites (Myiophanus sp.) cotlected and neconãed. Most of the emenging beetles wene ÍmmedÍatery pnesenved, in 70 percent alcohor_. The sex was laten detenmined (Section 4.1.2.A) and samples of females d.issected to dete::mine the stage of ovanian developnent (Section 4.1.3.1). snow coven affected sr.rvívar of ovenwinteníng adurts. A mean of 10'2 beetres (20.4 pencent sunvival) emenged fi:om each site that had snow nernoved on Jar¡uany 6, wheneas a mean of 25.6 beetles (st.z pencent su:lvÍval ) emenged fnom sites where the natunar snow cove' r^ras left (Table 8)' Fewen beetJ-es emenged fnom tneated sites thnoughout the May 1to l'{ay 24 ernengence períod (Figune 4). Since pnevÍ.ous ovenwintening studies had shown that 87.1 peneent of the ovenwintening adults wene found wíthin the top S cm of soíl (Section 4.1.1.1), it r^¡as not su:rpnisíng that snow nemoval dur,ing mid winten significantry incr:eased mortaríty. This indicates the Ímpontance of an insulating layen snow of to insects which ovenwinten in the soil. sunflowen fields tend to hoJ-d snow du:ring the winten d.ue to the tnash cover pnovided by sunfJ-owen stalks and their. cultune has been necommended fon this punPose (Putt 7972). Added snow coven would, thenefone, tend to favour" beetre sunvival. A neconmendation to decnease snow coven in ondern to increase montality of ovenwintening beetles wourd not be acceptabre because it would conflict wÍth cr:¡rent curtu::al pnactices. 85 Table 8. Effect of snow nemoval- on the ovenwÍntening sur.vival of adults of the sunfrower beetle, Zygognamma excramationis, Vlinnípeg, 7976-77 Numben of adults RePl-icate ffi snow nemoved2 1349 2293 322L7 4 1t 524tt 7 628:7s013 B2g7 926 10256 10 Ã-vãnãgã --ãslo- -ToJr.;,-- ?_guryiyal 51.2 20.4 r50 adults placed in é on Septemben 15, 1926. 2Snow cover r:emoved (fO - 15 cm) on Januany :t:l¡r{s¿¡s 6, 1977, on]y. significantJ-y diffenent (P=0.01, stúdeát t-test fon unpaired data). 86 Figrlre 4 ' Effect of snow eover on sunvir¡al of ovenwíntened. adults of the sunflowen beetle, Zygognamma excla¡Lqtionis Solid column -natural snow cover Broken column - snow removed ÎD =f t rl- o lto E zt May - 1977 B7 4.1.2 posthiben¡ation emergence su:rveys wene conducted to detenmíne the finst emengence of over"wintening adults, and a TU accumulation system using ain on soil tempellatunes was tested to pnedict finst emengence. Tnfonmation on the dr::ration ana paiter.n of posthibennation emengence was obtained fnom field surveys and f¡"om the 1976 to tg77 snor,¡ removal stud.y (section 4.1.1.3). 4.1.2.7 Date of flnst e¡nengence !g74 to tg77 Sunveys fon signs of fínst emeltgence of ovenwintening adults wene conducted in voh¡lteen sunflowen fields of south-centnal Manitoba du::ing the eanly spning of 1974, tg7s, ],976 and 1977. usua[y twice pen week, app::oxÍnately five to eight nandoinly selected fields wene examined by scanning volunteen plants for signs of feeding and/on pnesence posthibennation of adults. plants wene bnushed gently by hand dislodge to any beetres feedÍng on the undensides of leaves. Beetl-es obsenved were collected and pnesenved. fon laten examination. The stant of nating and egg-laying in these vorunteen fields was arso noted in each of foun the years. 0n every sunvey, at least 0.5 man hours wene spent seanching in each fÍeld. Signs of emengence by ovenwintenÍng adults wene finst noted in volunteen sunflowen fields of south-centnar Manitoba on May 27, llay 22, I4ay 2t, and May 11 fon the yeans 1974 to rg77, nespectÍvely. The mean date of finst emengence was, thenefone, May 20. rt shourd be noted that in 1975, evidence of feeding by posthíbennation adults was obser.ved on 8B l{ay 22, but it was not until May 27 that the finst adult was found. The ea::lien date was used ín subsequent analysis (section 4.r.2.2). În 7977, t¡. first beetle fnom the snow coven study (section 4.1.1.3) emenged on May 1 (Figune 4) but examination of volr¡rteen fields failed to show evidence of emengence until May 11. rn this caser May 11 was used as the finst emer:gence d.ate because it was based. on field surveys of volunteen fields as were the 1974 to 1976 dates. 4.1.2.2 connelation of accumulated TUrs to date of finst emengence to !977 .7974 A thenmal unit (TU) accumulation system was tested for use in pnedicting finst emengence of ovenwinteníng adults in south-centnal Manitoba during the yeans 1974 to tg77. Daily maximum and rninimum ain temperaatunes and soil temperatures (5 and 10 cm depth) denived fnom the Envinonment Canada !üeathen Station at the !Íinnipeg Inter.national Ainpont wene util-ized in carcurating the TUrs. The winnÍpeg Station was chosen because it was the closest one to the sunflower gnowing negion that neponted daily AM and pM soil ternpenatures. soil tenpenatur:es fnom the 5 and 10 cm depths r4rene used in calculating TUrs and tested fon pnedictíng emergence because these temperatunes would nost closely simulate cond.itions encountered by overwintening beetles since most beetl-es wene found at depths of 10 cm or? less (section 4.1.1.1). Because the lowen thneshold temper"atu:ne (tolo) for the overwintening stage lras not known, a numben of ar"bitnany ToLOts wer.e tested including 50 and 10oc fon ain TU accumul-ations, and 0o, oo and 89 soc fon soit ru accumur-ations. TUrs fuom Apnir 1of each yean to the date of finst emergence wene calcurated using the chmiel-lfir_son nodification of, the Sevachenian method (Sectíon 2.5.1.2). The finst of Apnil was used as a startÍng date fon TU accumulations because soil temperatur^es above 0o or ain tempeoutrro." above 5oc nanely occurned pnion to date that during the yeans 1924 to tg77. The avenage TU accumulation to first emergence fo:: the nespective ToLOrs for the yean 1974 to 1977 waç used to pnedict fÍnst emengence fon 1974 to 1977. The ToLO and tem¡leratu:re source combination with the snnlrest deviation of pnediction (in days) was chosen as the best fit The mean TU accumul-atíon to finst emergence varied aeconding to the tempenature sounce used (Air, Soil) and the ToLO used (fa¡fe g). Fon exampre, in 19740 first emergence was obsenved on lray 27, by which time 139 TUts wene accumulated based on ain tempenatu:r,e data (Ai::) and calculated using ê SoC thneshold tempenatune (5oC ToLO). Usíng the same system, TUts accumurated at finst emengence fon 1975, 1976 and 1977 wene 189, 205 and 241, respectivery, fon a mean of 1g4 TUrs (Air., soc rolo). simÍIanry, as shown ín Table 9, the mean numben of TUrs accumulated to finst eme¡gence fon the yeans 1g74 to !g77 was: g2 fon Ain, 10oc rolo; 235 fon soi1, 5 cm dgpth, Ooc roLO; t2B for soir, 5 cm depth, 3oc rolo; 75 fon soir, 5 cm depth, soc ToLo; 196 fon soir, 10 cm depth, Ooc roLO; 94 fon soil, 10 cm depth, 3oc rolo; and 49 fon soiI, 10 cm depth, SoC ToLO The mean TU accumur-ation fon each temperature sounce-Tolo combinatíon was tested fo:: accunacy in predicting finst emengence fon 90 Table 9. Date of finst emergence and. thenmar unít accumurations (ru ecc.) at fir"st emergence of ovenwintening .¿"ii"--or the sunflowen beetre, Zygognamma excramaËonis, in vorunteer sunflower" fields of so 4 to 1977 TU 4"..1 at fÍnst emênãG calcurated usm soil te tunes Finst emengence at ain tempenatures 5 cm dept 10 cm obsenved depth and ToLO (oc)z and tol,O (oc) and ToLo (oC) year date 0o 30 5o iõ-3tr-rõ 1974 t"Iay 27 139 40 -244 130 69 2t0 101 46 1975 Î{ay 223 189 79 239 139 91 192 101 61 1976 NIay 2! 20s 82 244 119 66 204 83 39 - 1977 May 11 247 727 213 722 73 !76 92 so Av. May 20 194 82 235 !28 75 196 94 49 Station. 2ToLO - lowen thneshold 3Finst tempenatune. emengence determined by evidence of feeding d.amage. 91 yeans the 1974 to í-977. Fon example, usÍng 194 TUrs (Ain, 5oC ToLO) pnedict to emengence in 1974, the pnedicted emengence date was .Ipne 2, six days laten than obsenved fírst emengence (May 27). The deviation of pnedictlon the r4ras, thenefone, six days. similanly, using 1g4 TU,s fon 1975' 1976 and 1977, the p::edicted emer"gence dates were {ay 20, l'{ay 20, and May gi ê deviation of one, one and two d.ays, r"espectively, fnom observed finst enengence. The total devíation of pnediction (in days) fonAinr 5ocToLo, was, ther^efoner 6 r t+L+2=!0. Figure 5 depicts the obsenved and pnedicted emergence dates for all combÍnations tested fon the yealas 1g74 to 1977 and also shows the amount of deviatíon, that is, the accunacy of each combination; In reviewing Figune 5, obsenve that the nost accurate combínation $ias soil, 5 cm, Ooc rolo (TUts accumurated = 235), since it pnedicted the obsenved. emeugence date fon thnee of fogn yeans (Ig74, 1975 and 1976) and ovenestÍmated the emengence d.ate by two days fon one yeån (1977). The total deviation of pnedíction was, thenefone, only (i.e.0 two days + 0 + 0 + 2). This combination (Soit, 5 em depth, ooc ToLo) iso thenefone, ::ecommended fon funthen testíng in pnedicting finst emengence of ove::wintening sunflower beetles in south-centra.l- Manitoba. Mone wonk is nequined to venífy and/on nodify the system to nake the pnediction more accurate. A spning sampling program fo:r posthibennation adults based on a TU accumulation system wouLd be mone accr::rate than a system based solely on carendan dates since the fonmen takes into account deviations in tenpenature. 92 Pigune 5' Deviations (days) of predicted fnom obsenved. emengence fon ovenwintening sunfl0wen beetles, zygog:ramma exclamationis, using mean emengence date and vaníous trreonnt unit accumulation methods as pnedíctons, tg74_!977 Predictor Value (Mean Emergence)= May20 (A¡r, s'C T'LO) =194TUs ---> (A¡r, to'c rlo) = 82 TUs ----> (Soi 1,5 cm, O'C t'to) TUs =23S -> (So¡l, g'C s cm, TLO ) = 12g TUs ...-> (so¡l,5cm,s'c t'to)=75 TUs --+ (Soil,tOcm,O'C T'LO) = 196 TUs -> (Soil,tocm,g'C T'LO) = 94 TUs -> (SoillOcm,s'C T'LO) = 49TUs -> May May 1974 1976 93 4 -1.2 -3 Dr::ration and pattern of posthi-bennation emergence The study on the effeet of snow cover on ovenwinteníng survival (Section 4.1.1.3) pnovided infonmation on the emergence pattern and the dunation of the emergence peniod fon ovenwintening adults. Since these beetles were sexed when they emenged, infonmation was also obtained on the nelatÍve time of emengence for males vs. femar-es. Ovenwintering adults emenged oven a 24-day peniod in the cages of the snov¡ coven study, wÍth peak emengence occunning 13 days aften first emergence (rigune 4, p.g6), and 50 pencent cumulatÍve emengence occunníng 12 days aften finst emergence. In orden to sex the beetles emenging fnom the snow nemoval and natural srrow ooven sites, a sear:ch was made for an extennal sex chanacten. Earlien reports on chrysomelids indicated that the shape of the fifth abdominal stennite could be used to dístinguish the sexes (weben 1976). upon examination, it was found. that the fífth abdominal stennite of the sunfrower: beetle female is ovate, ín view, along the postenior nangin, wheneas ín the mare, the posteníon margin is somewhat concave at the distal- pontion of the stennite (Figune o). This sexing chanactenÍstic was found to be 100 pencent accunate as venified by dissections. Most necentry Goed.en and Ricken (1929) used the shape of the fifth stennite as a sexing cha::acten for Zygognamma tontuosa Ovenwintening males ernenged one to foun days eanl-íer than femares thnough the initial emer:gence peníod but by May 13 the Propontions wene almost equal such that 50 per.cent cumul-ative emergence 94 Figu:re 6. ventnar view of abdominal stennites of female and male Zygognamma excrarnationis adurts. The a*row indícates the fífth stennite which is used as a sexing chanacten. Fema le Ma le 95 by both sexes oecun:red on the same d.ate (Figune 7). Collections of posthiber:natíon adults fuom vorunteen swrflowens d.u::íng the spnÍng of 1976 supponted the obsenvation that males tended to emenge befone females and that the sex ratio eventually appnoached 1:1 (nnle:female) ( ra¡re to ) . 4'1'3 rnitíation of posthj-bennation ovanian development and matíng Ovarian development was followed th:rough examinatíon of ovanies dissected fnom specimens collected at intenvals aften emengence in the spning. rnítíatio¡r of rnating was determined by the presence of sperm in the spenmatheca of females corrected in the spning since Ít was known that mating does not occur: befone hibennation in the falr (section 4.t-r-2). Thnee gr:oups of adults wene used fon this pr*pose. The finst glroup consisted of posthibennation adults coll_ected during May and June of 1974, 1975 and 1976. The fínst collection in 1974 wàs made May 27 and was mad.e up of the finst beetles seen on sunflowen plants Ín that yea:'. No beetles wene found duning a sunvey on May 25' so it was assumed that most, if not all, of the beetres collected on May 27 had emenged d,ning the p'evious two days. rn 1975, the finst corlection was made on May 30, eight days aften the finst signs of emengence of overwintening adults. Beetles wene also taken on May 25, 1976' foun days aften the finst beetres Ì¡ere seen on sunflowens. rn each of the three years, additional samples of sunflower: beetles wene collected fou:: to 22 days aften the finst evidence of beetle emengence. All females collected vüere examined to 96 Figune 7. Cumulative emengence of ovenwintened female and male adults of the sunfl0wen beetle, Zygognamma exclamationís, fuom the !976-77 snow coven study Cumulotive Percent Emergence o)o o o oo () (,| \ \.\. \. \. llq,t'..\..\j =oo I (o {o \,-_'\ \¡{ . :r=\. .\. (,l ,\. :\\ " \\!a \ l\) I o l¡ I¡a Irl I l\¡ CIl 97 Table Numben 10. and sex ratio of posthibennation adults of the sunflower beetle, Zygognamma exeÌamationis, coffe.ieã in the fierd in soffiãGlEìiEEa at inter vars fnom May 25 to June 6, tg76 tion date female Ratio (a: ç) May 25 85 51 1.6:1.0 May 28 59 49 7 .2:7 .0 June 1 86 61 June 1.4:1.0 4 13 15 0.9:1.0 June 6 62 Total 62 1.0:1.0 305 238 r.s:rl- 98 detenrnÍne the stage of oocyte development acconding to a systen suggested by Genben .t al (1979). They pnoposed two previtellogenic stages and fou:: vitellogenÍc stages distinguishabre by the size of the ultimate ooc5rte (Appendix 1). In addÍtion, the spenmatheca of each female was exarnÍned fon the pnesence or absence of spenmatazoa. Histologícal pnepanations we::e the same as descnibed in section 4.1 .1.2. The seco¡d gnoup consisted of adul-ts which had been corLected fuom the tg76/Ig77 snow coven study (Section 4.1.1.3). The collectíon consisted of 24 fema.r-es which had emenged between midday May 10 and nidday May 11, !977 ) and an additional 23 fernles which eme::ged between midday May 11 and mídday May 12, 1977. These newly_emenged females vrene presenved and subsequently examined to detenmine the stage of oocyte development and the pnesence or absence of spenmatazoa in the spenmathecae. The thínd Bsoup was also fnom the [g76/tg77 snoh¡ coven study (sectíon 4'1'1'3) and consisted of 40 females col-l-ected fr^om emengence cages at 24 h intenvars between midday May 13 and midday l,fay 16, rg77. six of fenrales the from this colrectíon wene kir-red and presenved. inmediately' whire the nenaind.en wene divided into four. gnoups and caged on sunflower plants with an equal numben of nnles. Thr.ee of the fou:: g::oups were praced in gr:owth cabinets at 13.s t 1oc, 20 t 1oc and 28 t 1oC, nespectÍvely, and a photopeniod of 1BL:6D. The for¡::th glroup was caged outdoons on sunfl0wen plants. A sample of three to five females was taken fuom each tneatment at two day intervars until the fírst eggs were noted 1n the nespective treatments. Femal_es wene subsequently examÍned to determine the stage of oocyte development. 99 4.1.3.1 Initiation of ovanian development in posthibernation femal-es vitetlogenesis (yolk pnoduction) was ÍnÍtiated eithen befone on shontly aften emefgence fuom híbe::nation (fa¡le tt). Vitellogenesis was obsenved in 15 pencent of the fernales collected and pnesernved. or¡ the finst day beetles were found ín the'fierd. in 1974 (r¡iay 27). By June 3, 1974, the ovaries of 97 pencent of the females e> the finst evidence of beetle emengence, all females collected wene in one of the fínst thnee stages of vitellogenesis. on May 25, !976, foun days aften finst emergence, 93 pencent of the fen,ales had ovanies cl-assed. Ín one of the Vitellogenic stages. Daily collections of fennles fnom the tg76/Lg77 sno$/ coven study supponted the obsenvation that Vitellogenesis was initiated veny close to the time of emergence. Fifty-foun and 57 pencent of the ferales collected fnom emengence cages on May 11 and 12, nespectively, we:re classed as fuevitell0genic, wheneas 46 and 43 pencent, nespectively, wene classed as Vitellogenic (Table 11). Food. was not pnovided fo'n these females; VÍtellogenesis was thus inÍtiated without feedÍng. vitellogenesis appeaned to pnoceed napidly at arl tempenatu::e ::egimes tested; rEture oocytes wene evident two to four days following emergence by the beetles (ta¡re rz). tn tt¡ese tempenatune tníals, food. was pnovided fon the females. Field obsenvatÍons fnom 1924 to r9?7 ft;rr.then suggested. that ovanian matunation was compreted and egg-laying stanted within one week Table t1" Date, number of females and oocyte dêvelopment in posthibei"hation females of the sunffower" beetle o Zygogramma exclamationis , tg74_tS7l Numben Date of females Nlay 27 , !974 26 (72)2 03 8s (e) 1s (2s) June 1974 (100) 0 0 0 3, 38 0 3 (100) 10 (100) (100) (1oo) B1 10o ) May 30' ts75 5 (1OO) o 0 +0 (100) 4O (100) 20 (10Ò) 'Jr:ne3'1975 11 (1oo) o 9(1oo) g(1ooi 9(100) g(100) o June 13, 1975 19 (roo) o 0 (1ooi 64 100 ) 5 0 5 (100) 90 100 ) Mav 250 1976 30 (97) o 7 (roo) 10 (67) 0 o (100) Mav 28, 1976 15 (100) o 13 (100) o 83 June 4' 1976 16 (100) o 0 87 (100) o 6 (100) o o 0 94 (100) Mav 11' !977 2a (n) o 54 (rs) +2 (to) + (100) 0 o ì*ay 12, 1977 2a (s) o 57 (o) ss (zz) 4 (0) 0 o 2Numbens in panenthesis refen to the iercentåg" ";-;"r"1""'ì;;; had ¡¿1s¿. '::ï:":?r;"i5r:;i:i:"rîå?::.1ã:r"". urtimate oocvte was classified ;;-ili"s in the particular Þ o 101 Table 12. Number" of females of the sunfr-owen beetle, Zygognamma with oocytes at a panti""rá"ffiË d'evel.pmentçIl1it*.i"li"=, when her-d at dj-ffenent tempenatunes fon 0_6 days after emengence fnom híbennation. Stage devé r of Time Numben Pnevitellogenesis Vitel.logenesrs ( davs ) of femal-es +ITIIIff t 13.50C 2 3 0 0 7 â T_ 0 0 4 0 0 0 2 0 6 e t 0 0 0 t t 7 200c 2 3 0 0 t 0 0 4 4 0 0 -- 2 t 0 t 6 5 0 0 2 t 0 2 2BoC -T- 0ut-of-doors 2 4 0 0 4 220 4 0 0 100 rNurnben of days since emergence fuom hibennation ovanies. till examÍnations of zClassified accondíng to a system pnoposed by Genben et al (lg7g). 3Numbens given as the number^ of females whose langestìtdmate ooeyte was classified as being in a pa::ticulan stage of devãtopment. t02 aften posthibernation emengence. rn 1974, 1g7s, 1976 and !977, eggs were fi:rst noted sevenr eight, fo':: and six days, respectively after the finst posthibennation adults r^rere notea (ta¡fe f S). (1977), Rogens in Te> 4 .1.3 .2 fnitiation of mating Males and females mated within the finst two days aften emengence fnom hibennation. on rray 27, 1974, the day the finst posthibennation adul-ts wene founð,, !2 pencent of the females examined wene found to have spenm in the spenmatheca and, thus wene known to have mated (Table 11). Resarnpling of the same site seven days later, on June 3, nevealed that of 39 females examined, all had mated. rn 1975, arr posthibennation femaLes had mated when collected eight to 22 days afte¡- emergence, whire in 1926, gg pencent of the posthibennation females had mated when colrected fnom prants foun to 14 days aften emengence. rn two gnoups that emenged in outdoon cages on May 11 and !2, !9771 13 pencent of the femares had mated withín 24 nof emergence. Rogens (1977) found that in a non-diapausÍng labo::atony cuJ-tu:re, neaned at 27 zoc and ! 14L:10D, mating usualry began approxinater_y one 103 Table 13. Dates of appeanance of adults and eggs of the sunflowen beetle, Zygognamma south-ceñffiîfrffiiexclamatíonis - in sunflowen fields ín Days to Last adults Days eggs finst e e esent t974 l(ay 27 June 3 7 1975 l{ay 22'r May 30 B July 18 50 1976 May 21 May 25 4 July 9 46 1977 May 11 tlay 17 6 ¿uly B 5g plants. " 104 rraften week after emergence. By emergencerr, he meant aften pupar eclosion, I'aften as distinct f;nom posthibennation emergence, as used. in this disser"tatÍon. rn Manitoba, posthibennation emengence is the most impontant refenence point since thene-is onry one generation pen yean and mating and oviposition are initiâted aften hibennation. rn the pnesent study a non-diapausing labonatony cultu::e was established (section 4.1.9.5) in which mating was initiated seven to 11 days aften pupal eclosion; this agnees with the wonk of Rogens (1977). 4.1.4 Mating and egg-layÍng Thnee þnoups of adurts wene used to detennine ¡nating fnequency, natíng behavioun, ovipositíon fuequency and behavÍoun, ovíposition penÍod, and fecundíty of the sunflowen beetl-e in the 1abonatony and in the fieLd. The finst gnoup consísted of 13 pains of adults which oniginated fnom lanvae that had been neaned individually on sr¡nflowen plants in a contnolled envir"onment chamber" in 1974, whene the tenpenatune vras 25 zoc ! and the light cycle was 16L:gD. These adults wene in diapause fon 10 weeks (two weeks at 10 t 1oc, six weeks at 2 t 1oc, and two weeks at 10 t 1oc), aften which they wene exposed. to a hígh tempenatune (30 t zoc) to bneak dÍapause. This method of bneaking diapause !Ías ,,.{Fi similan to that descnibed by De llilde (1957) for the Col_onado potato beetle. Foltowing the tenmination of d.iapause, the beetres v¡ene tnansfenned to each of sevenar grass cultune dishes, 5 cm in height x 10 cm in diameten, pnovÍded with leaves of sunflower. (cv. penedovik) 105 fon food and oviposition, and uraíntained in a contr.olled envinonment chamben at 25 2oc ! and 1gL:6D photope::iod. Each day the reaves wene neplaced, the numben of eggs counted, and a necond rnade of the pains in eopula. The second gnoup consisted o'f 20 pains of beetles collected on May 25. 7976, and placed sepanately on sunflowen plants (cv. penedovik) 15 to 30 cm high, outd.oons at Glenlea, Manitoba, in aluminum scneen cages measuníng 15 cm in diameten x 35 cm in height (figune 3b, p.57). These beetles were corrected foun days aften the first beetres wene seen in the field. They we¡,e tnansfenned. to new prants every second. day, and a necond rade of the numben of eggs on the plants and of the pai^r"s in copula. small- succul-ent sunfl-owen plants wene avaiiabLe continuously since seedÍng was canr.ied out at seven to 10 day intenvals th:roughout the expeniment. DaÍly weather data wene obtaíned fuom weathen neconds naíntained at Glenlea, I'{anitoba. At the termination of this expeniment continuous neconds had been obtained fon only foun fenales' most of the othen females had escaped when cages wene toppred dur.ing a sevene nainstonm. The thind gnoup consisted of 20 pains corlected on May 24, !g77, about 13 days aften the finst beetles emenged in the field. They wene nraintained outdoons at Glen1ea, Manitoba, in the same cages and handled in same the nannen as those of the second group. Mating and ovÍposition neconds wene obtained fnom 12 females du:ring the cou:rse of this expeniment. 106 In addítion to these expeniments, sunflowen fields wene examined fon eggs duning May to August to d.eter.mine the penÍod du:ring which eggs r^rene pnesent in the fíeId. 4.1.4.1 Mating behaviou¡ Mating behavioru: appeaned to be símple. The male mo,nted the female donsally imnediately upon contact (Figune Ba)r gtrasped the elytna of the fenrale along the late::al edge, and. insented the aedeagus. pairs nemained in this position for peniods of o.s h on longen while the female continued to feed on seedlíng sunflower". rntnuding males wer"e often noted to disnupt mating pains. The "intnud.err? used his mandibles gnasp to and pull the regs and antennae of the rrin copurarr male (Figune 8b). often the intnuden and the in copula male woul-d continue to battl-e even aften the female had left (Figune gc). A veny simple mating behavioun has also been d.escnibed fon Zygogramma sutunaris (ripen 1975) and. Z. disnupta (pipen 1978). 4 .t .4 .2 Mating fnequency . Males and females mated mor-e than once. rn a labonatony study Ín 1974, whene caged pains were obsenved fon about one houn pen day a mean period of 63.2 days, the avenage number of observed copulations pen pair was 33.4 with a nange of zeno to 57 (ta¡te f+). Matings were noted on 50.8 pencent of the obser.vation peniods when both male and femare wene alíve. rn fÍeld studies in 1976 and 1977, where obsenvations wene rnade every second day oven a per.iod of 62.5 and 42.5 days, respec- tively, the aver"age numben of obsenved copulatíons pen pain was g.g with a nange of eÍght to 12, and 3.4 with a range of zeno to nine, nespectively to7 Figune B. Mating behavioun of the sunflower beetle, Zygognamna exclanationis_ (A) Male on female in nating position ( x 2 ) (B) "Intnud.ing" male pulling at the appendages of an trín copura?r n're while the rrin copura, male continues to mate with a female ( x 2 ) (C) Two nnles fighting aften fenoale has gone ( x 2 ) Table 14. Pneovipositionr and ovipositÍon peniodsr egg pnoduction, number fnequency rnating2, of obsenved matings, of and egg_fayings fon 13 pai::s (te + 1¿) of the sr¡nflowen ZJ¡gogra¡nma exclamationis, beetle, caged on sr:nflowens in a contr.olled envinonment cabinet at @er.iod of 1BL:6D n1 o s Matings obsenve of days numben ÞFeõçï S TT ]. on1 0vi sitlon Tota Numben %2 Laids t2 89 3587 40. 3 1.3 57 62 .6 100.0 2t 39 7421 36 .4 3.9 5 18. 5 89 .7 3q 70 2598 37.1 t.7 57 78. t 100.0 42 48 1081 22.5 1.6 36 76. 6 .0 59 67 22!8 1oo 33 .1 1.5 50 75. e 100.0 6Z 15 303 20.2 co 7Z 94 3 37 .5 100.0 2959 31. 5 r. t 36 32.4 8t 65 2l84 98.9 Qr óó.b 2.7 40 59 .7 oe o rJ 73 1798 24.6 1.5 58.9 98.6 103 58 1869 32,2 2.4 30 50 .9 96.6 tt2 106 3365 t24 31.8 1.4 57 56.4 97.2 51 ]-897 37 .2 ¿.ó 135 14 10 52 .6 100.0 260 18.6 3.9 0 0,0 92.9 Meqn 2.s 60.7 40 -ã-3;4 196s 30.7 5õ;8-- õi;5-- ,l:i::l:_:I_u:lllobsenvations:i:::::i':'.'::T.,3":^t:1-:-t?:Ilto:l3ti3n .emels:n:e-r¡rtil the start or egg-rayínf calculatíon , .each .i J;;;-i"r,-a"".ii.ni=oi';;i";'n:iå"1iållt".."u in copula. based on the peniod dur.ing whích rnar-e was ar_ive. 3Pencent of days, thnoughout th. oviposftion f"oioa, o., eggs wene "hi"h-.ee" laÍd. oF @ 109 (Tables 15 and 16). Matíngs were noted on 30.2 and 13.4 pencent of the obsenvation peniods when both the male and female wene alive. 4.1.4.3 Oviposition behaviour rn the fieldo eggs r4rere usua.lly laid on the stems and on the ventral sulface of the reaves: they lrene rarery noted on the donsal sunface. Eggs wene often rocated. in depnessions such as along the veins on the ventral sunface of leaves, the donsar sunface of the l-eaf petiole, and folds in spent cotyledons. rn a composite sampre of 150 plants taken fnom a commencial field at Lowe Fanm, Manitoba on June 7 and 14r 79771 46.8 pencent of the 498 eggs examined, wene found on the stem whíle 47.7 and 5.5 pencent wene found on the leaves and eotyred.ons, respectively. Eggs wene usually positioned at an angle of appnoximately 45o to the sunface on whÍch they wene deposited and wene firmly fixed to the plant by.a crean secnetion. Although eggs vrere raid singry, innegulan línes on groups of eggs we::e often noted. 4.1.4.4 Fnequency and pattenn of egg_laying Once oviposition was initiated, females laid eggs alnost eveny day duríng the oviposition peniod. In studies ín 1974 , 1976 and 1977 eggs were found gg on 97, 95 and pe:rcento nespectively, of the days on whích counts wene made (Table 14, 15 and 16). The pattenn of egg-Iayíng r\ras obsenved. fon 13 femares caged. on sunflowens in a contnolled environment chamben at 2s ! 2oc and. a photopeniod of 1BL:6D. Egg-laying neached a maxirnum of 30 to 40 eggs pen ferare pen day duning the fÍnst two weeks and nemained at that Table 15. Pneovipositionl and oviposition periods¡ egg pnoduction, numben of obsenved fiequency or mating2 , egg_rayinf -iJ"-i-pï;" -a -;'f matings, Zygognanrna "r,d ie ñi- th" ;;;ioiJo.^îà"tru exclanationis, cãfea on sunfrowenå out-of-doors , at GLenlea, l4anitoba in 1926 Pain peniod gg pnoduction . lqdysl(davs)ys _ Two-day petiod =-:Ys_ 5 8 9!2 31.5 ùo 2 4u çtttrr, ::"-cE- :.-': 3. Iö 15''/tsL¿' .7 t t2rz72 3'l.537.5 100.0 54 65 7 24.9 ó.3. - 3 õ3 t272Lz '¿.2 10Lu 3+.534. s o0 62aic.. ::,1904oat, ::.29.2 : 3.5o'c 100.0 4 o n^ .:.:: ::': 14.61+.b I 25. B e8.1 70 1400i+uu "40 .0 4.6 .,'I'X : 1:.9 15 .9 9,.8 30.r----98.8 lBeetl-es collected 4 days aften finst beetles missed, noted in fier-d; pant of preoviposítion peniod likely 2Percent of obsenvations, each of about t h duration every second copuJ-a. carculatíon based d.ay, on which pains wene noted in 3Pencent on tJre period dur-ing which mare was a'ive. of 2-day egg-raying peniodã on which .[g" "ãr. Iai¿. F oÞ Table 16. PneovíposiiÍon1 and oviposition peniodsr egg pnoduction, numben of observed fr.equency of mating2, matings, and egg-tayíngs fon i2 pains (te + 1o) of the sr¡:rflowen beeile, Zygogr.am¡na exclarntionis, caged on sunflower:s out-of-doons at Glenleà, Manitoba in tgZZ Pain p."lgq ttú"o Gqy" ) _ to..t Ëã-.-..---.--.G- ,.".r/¿-:, ffi %, .rr" ruru" ! - 58 742 25.6 3.1 12.8 4 7.3 100.0 2 - g2 459 28.7 3.6 14.3 4 3 - 58 23.5 100.0 541 !8.7 2.8 9.3 5 18ì5 92.6 4 - 62 7!3 2g.o 3.0 11.5 s - 58 I 29.0 100.0 1554 53.6 5.0 26.8 5 .,7.2 100.0 6 - 58 78,- 26 ,s 7 3.0 13.5 5 t6 .7 100 .0 - 16 rg2 16.5 4.0 8.3 t tt.t B - 30 493 100.0 9 32.9 3.9 16.4 t 6.7 100.0 - 34 470 27.7 3.7 13.8 o 0.0 10 - t6 248 31.0 100.0 tt 4.2 15.5 0 0.0 100.0 - 46 830 36.1 4.8 18.0 4 17,4 t2 - 4 666 o1:Z_____g:, 100.0 tsea:: ------: -----+2;5------60-o'---ãõ;O--- --ãi------iãis.g 3 10.6 100.0 . õ------ã;¡-----îã;4------nn:4-- 2Percent of obsenr¡ations, each of about t h duration ever:y d.ay, on which pairs copula. calculation based on peniod ""ãorra wene noted. ín 3Pencent the dunÍng which maie alive. of 2-day egg-raying peniod-s or, "nià .!g" *""" Iaid. F F lr ) 7!2 level- for sunvíving femares duning most of the nemainden of the ovÍposition peniod (Figune s). The avenage daily egg pnoduction fon the 13 individuar fernres nanged fnorn 18.6 to 40.3, whire the ovenarr avenage was 30'7 (Table The gneatest .14) ' 24 h egg pnoduction :recor.ded, fon an indívidual female was 7g. Mean dairy egg pnoduction fon sur"viving femares dnopped aften the 84th day; only three fernal_es wene al-ive (rÍgu'e g). These thnee femares appeaned to be near^ the end of thein r:epnoductive life. Fon the g:r,oup as a whore, thene was a gnadual decnease in the rate of egg-IayÍng aften the thind week because of montality of females. rn a field study in 1g76, egg-layÍng also neached. maximum cunÍng the finst two weeks of ovÍposítion and appeared to decnease gnadually aften the founth (Fígure week 1O). The pattern r^ras not as wel1 defined as ín the pnevious study because of gneaten vaniability in daily egg-raying. This was appanentJ-y caused by vaniation ín outd.oon tempenatu:res. Genenalry, high nates such as those obsenved. on days 10, 26, 44 and 46 coincÍded with above avenage temperatures, and the row Ilates on days 20r 22r 24r 32 and 34 with below average tempenatunes. The avenage daíry egg pnoduction fon four: females in the fierd study nanged fnom t2'2 to 20.0 with an ovenar-l avenage of 15.g eggs pen femal-e pen day (Tab1e 15). In a field study, Ln 1977, it was not possÍble to dnaw conclusions on the pattern of egg-laying because the finst pant of the ovÍposition pe'iod (penhaps the fÍnst nine to 11 days) was missed (Figune 11) The ' avenage daily egg pnoduction fon the 12 individuat_s tt3 Figr::ne 9. Egg-laying pattern fnom the tíme diapause ended untÍr the end of the oviposition per.iod for. 13 females of the sunfLowen beetl_e, Zygogramma exclamationis Eggq/Fema le/Day ool\'O) c, o Ø Ll4 Figune 10. Ëgg-raying pattenn fon fo'n fe¡rnres of the sunfrower beetl-e, Zygognamma exclamationisn kept outd.oons at Grenlea, Manitoba, Lg76 25^ o 20J. ct E 15(,t- I ôo 5 c oTU = an o based on initial o number of females ol --Pattern ò o E o lÀ ) 40 cn ct) l¡¡ Days tL5 Figune 11. Egg-rayíng pattern fon twelve females of the sunflowen beetle, Zygognanma exclamatíoniso kept outdoons at GrenJ-ea, Manitoba, !977 25 .o cü 20 E o l- t5 à o o Pattqrn based on initial c number of females o o u, -- = o ô ôl ò'o $ E l¡o )ro o) o) l¡J Days 116 followed in the 1977 study, nanged. f::om g.3 to 26.8 with an ovenar_r_ average of 14.2 eggs pen fernale per day (tabte 16). " Fenales usuarly died within a few days of termínation of oviposítÍon' Twenty-foun of the 29 fernares in the thnee ovipositíon studíes died. within fíve days of compreting oviposítion. rn the contnolled study (Table 14), thnee femares of pain nunbens seven, nine and 11 wene still arive when the expeniment was'tenminated on the 116th day; none had oviposited d'ning the pnevious 15, 3g and seven days, nespectively. one fe¡nal-e of pain number: fou:r in each of the 1976 and. 1977 studies went into the soil a few days aften taying the rast eggs and did not neemenge. rt is not known whethen these five females had eompleted ovipositíon' or whethen they had entened a second diapause and woul-d have inÍtiated oviposition again at a r_aten date. (1937) Dick descnibed foun types of ovÍposition cycres in coleoptena. The sunfr-owen beetre cyere apparently Ís typical of his second type whenein femates rive fon a rerativel-y rong peníod of time and produce eggs continuously dwing most of the time. rn a founth typer fenares lay more on less continuously in two or more seasons sepanated by a peniod du:ning whÍch ovíposition ceases. The fate of the fÍve femares in the thnee oviposition studies noted above is unknown, but had they entered diapause fon a second. time and subsequentry laid e88sr the oviposition cycle would be typical of the founth type. Both types of oviposition cycres have been observed in chrysomeridae (¡íc¡< 1937; waloff and Richands 1958; Balachowsky 1963; lIellso et al 1973i ushatinskaya 1976). Moneoven, both types ar.e found. wíthin some 777 chnysomelid specÍes. ïn the Colonado potato beetl-e, fon example, some fernales only 1ay dr::ring one yearô and othens lay in two on more years with a diapause phase occunning each yean (Ushatinskaya 1976). 4.1.4.5 Fecundity The avenage numbe:: of eggs per fen'nle pnod.uced in the controlred envínonment study was 11965 þ¡ith a nange of 260 to 3r5g7 (Tab1e 14). In the fíeld study, in 1976, femares raid an avenage of g6g eggs with a nange of 657 to 11400 (Table 15). In 1977, females lai.d an avenage of 636 eggs with a range of 132 to 11554 (Tabre 16). Females kept in the controlled environm.ent chamben thus pnoduced two to thnee times as many eggs as those in the field studÍes. However, since ovíposition pnobably was Ínitiated in the 1977 gnoup pnion to the time of cor_lection, the numben of eggs ]aíd likely was somewhat greaten than indicated. (1922) criddle found that, in captivity, one femare sunflowen beetle laid 116 eggsr but he believed that she had laid a number: of eggs befone being caPtuned. on the basis of this datao he stated that it was pnobable that the sunflowen beetle deposÍts at r-east 200 eggs pen female. The pnesent wonk shows that the beetle has the potential to lay êD êvê,,- age c10se to 2,000 eggs pen female and that some individuals may ray as many as 3'000 to 41000 eggs. However:, nesurts of field exper:iments suggest that this potential ís not nealized in the field; neventheress, the sunflowen pnobably beetle lays a rangen numben of eggs than suggested by cniddle. (tgzz Roge:rs ) arso showed that fenrares of the sunfrowen beetle have the potentíal to lay a range numben of eggs. rn captivíty, in Texaso the avenage numben of eggs pen femare fon 30 females v¡as rro27, and the langest number: of eggs deposited by a fenale was 41131. t7B 4.1.4.6 Dunatíon of the oviposition peniod The dr:ration of the oviposition peniod in captivity was rongen than that in the field. rn the contnorled envir:onment study, the average dunation of the oviposition peniod was 60.7 days with a range of 14 106 (ra¡re to t+). The dr:¡atibn of the oviposition peniod fon the gnoup was 106 days. The avenage dunation of the oviposition peniod in the field studies, in 1976 anð.1g77, was SB.5 (nange 52 to 70) and. 42.5 (nange 16 to 58) days, nespectivety (Tabt_es j_5 and 16). The du::ation of the ovipositíon peniods fon each of the two gnoups was 70 and 58 days, nespectively. rn surrfrower" fields, eggs were finst obsenved on May 30 in 1975, on May 25 in 1976 and on May 17 in 1977 (rable tg). The rast eggs wene seen on July 1g, g and B,:respectívery, in those yeans. Thus: egBS were pnesent in the fier_d fon appnoximately 50 days in 1975, 46 days Ín 1976, and 53 days in !977. Howeven, the dr:¡atíon of the ovíposition peniod fon each of the thnee yeans r.¡as sevenal days shor:ten than the data suggests because the eggs do not hatch until about one week aften they are laid (Section 4.1.5.3). Neventheless, it is cr-ean that the oviposition peniod in the fietd nonmally ís of six to seven weeks du::ation. Acconding to cniddle (tszz), ad.ults of the sunflowen beetl_e emerlge fnom hiber"nation in June and lay eggs fon two on more weeks in l-ate June and July in Manitoba. rn the pnesent study, beetres wer.e found to emenge eanlÍen and to lay for. a longen peniod of time than wene those'epor:ted by cniddle, but a July tenmination date for oviposition is Ín agneement. Adult emergence occu:rned. in the last half 779 of May in 1974 1976 to and the finst har_f of May in rg77. The dunation of the oviposition pe::iod as noted. was six to seven weeks, and the avenage du::ation of the oviposition peniod. in the thr"ee oviposition studies was between one and. one-har-f. and two months. ït appears that cnÍddre may have missed the eanly appeanance of the over"wintened adults and the inÍtiation of egg-laying on erse he may have been dearing with a population that emenged several- weeks laten than those in the present study. (1936), Ualken in Kansas, stated that eggs of the finst gene::ation r.rere laid fi:om June 20 to July 15 (ZO days) while Rogers (7977), in Texas, reponted that the average dr::ration of the oviposition peníod for'30 su¡flowen beetle females in captivity was 75.6 days Thís companes with 60.7 days in the contr-olled. environment stud.y neponted above. 4.1.5 Egg stage 4.1 .5 .1 DescnÍption Eggs laíd duning the fir.st two to thnee days of the post- híbe'nation pe'iod r^rere oraange, but ther.eafter wene cream, and. wer.e oblong to oval with slightly tapered ends (Figune tb, p.2). The eggs had no obvious extennar mankings but hexagonal-shaped cerls wene obsenved on the sunface of the eggs when viewed thnough a low-powen dissecting micnoscope. The mean length (t Se) of a sample of 100 eggs was 1.33 t 0.01 mm (nange 1.1g to 1.59 mm) and the mean wid.th vras 0.61 J 0.01 nm (nange 0.54 to 0.67 mm)., These measurements are cl_ose to the value of 1.5 to 2.0 mm long neponted by Westdal (fgZS), but ane less than the estimate of 2 to B mm long reponted by Wal-ken (1906). 120 4.!.5.2 Rate of development at vanious constant temperatur:es The incubation period of the eggs was determined at each of four constant tempenatu:res. A total of 391 eBBSr 12 hou:rs oJ-d, wene removed fuom a stock culture of the sunflowen beetle (Section 3.1.1) and 30-35 eggs were placed into each of !2 glass vials (fZ mI) stoppened with cotton-batting. Thnee vials with a total of about 100 eggs, were placed in each of fou:: chambers (Convi::or:@) treta at 16 t toC, 20 ! LoC, ZS t toC, 28 ! 1oC, nespeetively, with a photopeniod of 16L:BD and a RH of appnoximately 70 pencent. The contents of the vials were examined at 12-hou:: intenvals; newly-hatched l-arvae wene removed and neconded. Iühen no lanvae had emenged fon five consecutive days in the respective chambers, âDy renainíng eggs lrere examined to determine the number: without embnyos, and the nunber. that contained embr:yos that had failed to emerge Reaning temperaturse had a significant effect on the egg incubation rate (ta¡le tZ). Eggs maintained at 16,20r 25 and 2BoC nequined a mean of 13.5, 7.9, 5.6 and 4.5 days, respectíve1y, to hatch. Rogens (tg77) found that the incubation peniod fo:: a Texas sotrce of the sunflowe:: beetle requined 5.4 t O.f days (mean t Sf) when rea:red at 27 ! 2oc Of the 391 eggs used in the incubation studyo 74.2 percent hatched, 10.5 percent contained developed embnyos that failed to emerge, and 15.3 pencent showed no embr:yonic devel-opment (fa¡fe fe). The greatest percentage hatch (gO.+ pencent) occu:rned at 25oC, wheneas the lowest G7.7 pencent) was at 16oC. The numben of non-viable embnyos t27 Table 17. fncubation peníod fo:r eggs of the sunflowen beetl-e, Zygog:ramma exclamationis, at four tempenatures Tempenatu::e Du:ration ( days ) (+ 1oc) Numben of eggs 16 69 13.5 + 0.1 12 . 5-15. 5 20 77 7.9 + 0.1 7.5- 9.0 25 74 5.6 + 0.1 5.0- 6.0 28 70 4.5 + 0.1 4.0- 6.0 !22 Table 18. Pencent hatehing in eggs of the sunflowe:: beetle, Zygognamma exclamationis, at foun tempenatunes. Temperatune eo 9o not hatched (t toC) numben of eggs hatched 16 702 67 .7 14.7 t7 .6 20 101 76 .2 8.9 14 .9 25 92 80.4 4.4 75.2 ---39 -- -- 99------29:9------19.1-.------19:l----- Total 391 74 .2 1 0.5 15 . 3 123 was about the same at 16 and 28oC, but substantially greater than at 20 on 25oC, penhaps indicating the tempenatu¡e limits for: optimal emb::yonic development. 4.1.5.3 Estimated ToLO and TU nequí::ements Results fr.om the constant tempenatune tnial (Section 4.1.5.2) wene used to estimate the lowen threshold tempenatur"e (folO) and the theonetical thermal r:¡rit (Theon. TU) nequínements fon the egg stage of the sunflowen beetle. The ToLO was detenmined because it ís requíned fon the forrnula used to calcul-ate TU accumulations in the field (Section 2.5.1.2). As discussed, (Section 2.5), TU accumul-ations have a numben of p:ractical uses, such as piedícting the time of hatch in the field. The ToLO was estjmated acconding to the X-intercept method of Annold (fgSg) (Section 2.5.1.1). Using the data presented in Table 16, a linean ::eg:ression equation r^ras calcul-ated with X=temperature in oC, and Y=1/Days (i.e. nate of development) such that: X ,l 16 0 .07386 20 0 .12595 25 0.17953 2B 0.22321 Thus Y=a+b(X) (1) Y = -0.1203 + 0.0121X , 12 = 0.997 Using Annoldrs method, ToLO was estimated by determining the X-intercept of equation (1), that ís, fon Y=0, X=ToLO= -1. The::efore, fon the egg stage of the sunflower beetle: rolo -3= 9'1?9? s.eoc = b o -0727 = t24 In Figune 12, the linean negnessíon line fon the nate of development fon the egg stage is plotted (curve B), and the ToLO (X-intencept) shown. Curve A (Figune 12), which is a plot of the estinated development time, in days, fon the egg stage at vanious constant tempenatures, r^ras calculated using equation (1). Fon example, at x = 17oCo Y = -0.1203 + o.0t2t (tl¡ = 0.0854. Thenefone, the developmental time in days at 17oC = t/0.0854 = 7!,7. An estimate of the Theoretical thenmal units (Theor.. TUrs) nequired to complete egg development was calculated usíng equation (1) and solving fo:r: r= ! b O.OtlT = 83 TUrs In the labonator"yr eggs of the sunflowen beetle, thenefore, requined 83 TUts above a threshold tempenature of 9.goc to complete the incubatíon peniod. Sunflowen beetle eggs were usually present Ín the fiel-d fnom the end of May tiIl mid Ju.].y (table 13, p.103) with the nrajo:rity of eggs being laíd in conrnencial fiel-ds duning June. The mean daily ain tempenature in south-central Manitoba during the month of June is nor"mally between 16.5 and 17.0oC. Thenefor"e, using equation (1)o the mean developmental time fon the eggs would be between 12.6 and 11.7 days. Howeven, the actual temperature that eggs would be subjected to within the microclimate of a seedlíng sunflowen cnop could be somewhat highen than that r.econded at local meteonological statio¡:s. Buchen et al (1981) neponted a 1 to 2oC incnease in mean temperature necondings 10 cm above the soil sunface in a napeseed cr.op in comparison to ain tempenatune 125 Figure 12. Days tí1I hatchíng and nate of developnent of eggs of the sunflower beetle, Zygognanrma exclamationis, at constant temperatunes EGG STAGE I \ T"= 9.9'C \ T.U.'s = 83 Y \ r26 necondings from a local meteorological station. Such diffenences could be expected Ín othen such as sunflolrel?s, but detailed studies ",oop", wourd be r:equined to determine the nagnitude of these diffe::ences at vanious times duning the gnowing season. An estirnate of l8oc thus may be a mone nealistic mean tempenature anound sunflowen beetle eggs in June in south-central Manitoba. The estimated incubation peniod at 18oC was 10.3 days. Ïüestdal (1975), estimated the incr:bation peniod to be about one week in Manitoba wheneas lüalken (fgSO) estirnated foun to five days fon the incubation peniod in Kansas. Both estimates a::e possibte depending on the pr:evailing temperatunes at the time of obsenvation. 4.1 .6 La:rval stage 4.1.6.1 Descniption Newly-hatched sunflowen beetle larvae ane about 1.50 to 1.75 urn long. The head capsule is bnown while the body is a light yellor^r to cream wíth no dístinctive mankings. The body fonm is slightly cyphosomatic (hump-backed) and somewhat fusiforn (tapered at the ends). Thene are thnee pains of well-developed legs on the thorax and a bifid process (suckiág disc) on the ventor of the last abdominal segment. This bífíd pnocess is used as an aíd in locomotion. The young lanva appears gneenish-yellow after feedíng stants because the green food material within the digestive traet of the larva ís visíble through the thin íntegument (figure 7c, p.2). Because thene is no food in the digestive tract at molting, the lanva appears yellowish just befone and aften nolting. Arso, aften each rnolt the head capsule is yellow for a t27 short peniod until pigmentation ís eomplete. These colou:r cues ar.e of aid in detenminíng when molts have taken place. Ful1y developed larvae are similar to first-insta:: lanvae except that they measure appr"oxÍmately eight to 10 mm in length and ane mone cyphosomatic. Matune lanvae attain a yellowish appeanance just befone the subtet?ranean pnepupal stage due to an accumulation of fat tissues beneath the integument. 4.1.6.2 Lanval- behaviour and feeding Sunflowen beetl-e lanvae ane noctunnal feedens. Duning the day they nemain relatively inactive and congregate anong the leaves of the te::minal bud, while at night they move onto the leaves to feed. During laten stages of development lanvae continue to exhibit this appanent negative phototactic response and duning dayÌíght the head is di::ected away fnom light. During the day the larvae ane found among the bnacts of the developing flowen bud (Figune 1c) on in the leaf axils. This behaviou:: has been noted by llestdal (1975) and Rogens (!977). While feeding, the lanvae chew a hole thnough the leaf. With continued feedíng and expansion of the leaves, the leaves take on a shot-hole appearance (Fígune 2b, p.4). This differs fnom danage caused. by adults which feed on leaf rnngins (Figure 2a). Vlith lar:ge populations of lanvaeo feeding can be so extensive that plants may be completely defoliated with only the stalk, petioles, leaf veins and terminal bud nemaining intact (Figure 2c). Death of the plant due to defòliation by the sunflowen bêetle was not noted duning thís study. t28 As noted, although leaf damage may be sevene, damage to the. terrninal bud is usually l-ess severe and seldom pnevents head development, flowering and seed pnoduction. This appanent sunvival techníque of the sunflowen beetle to ensure a continuing food supply has been noted pneviously by Bnísley ( 1925) 4.1.6.3 Numben of instans The numben of l-anval instans r^ras detenmined finstly, by head capsule measunements of 400 fÍeld collected lanvae, and secondly, by nearing over 100 lanvae individually in the laboratouy and noting the nunben of molts. Dtr::ing lanval development the sunflower: beetle passes through four instans which can be distinguished by the hrÍdth of the head capsule (tabte 19 and Figune 13). The avenage head capsule width for each of the fou:: instans was 0.478,0.678, 0.980 and 1.448 mm, nespectively. The head capsule gr"owth nate between molts was, thenefone, !.42, 1.45 and 1.48, respectively between each mo1t. These r"ates agllee with Dyarts nute (Dyan 1890) which states that the gnowth nate of successive instans of some lanvae is nepnesented by a geometnic pr:og::ession, appl3oximately by a factor" of 1.4, assuming that no head expansion occuns duning each stadÍa. Rogens (1977) neponted that thene r^reue fou:: lanval instans with head capsule widths of 0.45, 0.80,. t.!6, and 1.58 mm, nespectively. The means diffen fnom those neponted henein, but Rogens was measuning head casts of a labonatony cul-tune of a Texas populatíon whíle in this dissentation measur"ements wene based on head capsules of pneser:ved 729 Table 19. Mean, standand ernon and r.ange fon head capsule widths of the four: lanval insta::s of the sunflower beetle, Zygogramma exclamationis . Head capsule width (mm) fon larval instàr'È1 - Ln L. L. Lr. Mean 0.478 0.678 0.980 1.448 s.E. o.oo1 0.002 o.oos 0.010 Range 0.459-0.514 0.627-0.724 0.892-1.097 1.216-1.665 N 100 100 100 100 tLr, Lr, L3, L.¡ = first to founth lanval instar 130 Figune 13. Head capsule widths of the four larval insta¡s of the sunflowen beetle, Zygognamma exclamationís 50 30 o Ê o C' o L IJ. 20' 10 .t. .ss .+a .st .68 .ia .Be r.óo rh u Head Capsule W¡dth (mm) 131 specimens fnom a field population collected in Manitoba. T.he d.iffenences o ther:efore, nray be due to diffenÍng geognaphic populations and/on different handling and measu::ing techniques. AIso, the rate of growth of head capsules as neponted by Rogens (tglZ ) vanies considenably fnom Dyants factor: of 1.4 4.1.6.4 La::val development during labonatony neaning 4.1.6.4.1 Rate of development at var"ious constant tempenatures The dur"ation of the la::¡¡al stage of the sunflowen beetle was determíned at each of thnee constant tempenatures. Lar:vae less than 12 houns old wene ::emoved fnom a stock cultune and placed one to a plant on sunflowen seedl-ings, cv. Penedovik, in gr:owth chambens (Convinon@) at each of 15 J toc, 20 ! 1oC, and 25 t 1oC with a photope::iod of 16L:8D and a RH of appnoximately 70 pencent. A totaL of 42, 40 and 40 finst-instar lar"vae were initially Íntnoduced to the respective tempenatune negimes. The sunflowers on which the lanvae were neaned wene g::own in a fl-at in a gneenhouse. Seedlings, in the t!ío to foun leaf stage, wel?e nemoved fnom the flat, and aften removal of soil fnom the noots, !,rere placed one to a flask in 50 mI Enlenmyen fl-asks containing tap water'. The mouth of the fl-ask was stoppened with cotton-batting to keep the seedling secure. The seedlings wene positioned on a metal tnay in a mannen such that thene was no contact between plants (Figur:e 14a). The lanvae wene placed on f::esh plants every four" to eight days dependíng on the amount of feeding damage and/or the genenal conditÍon of the t32 Figure 14. Mate::ials used in neaning the sunflowen beetLe, zygogramma exclamatíonis, fon the constant tempenatune tnials (A) Seedling sunflowens used to nean 1anvae (B) Pl-astic containens with noist ,r"oriå,¿ite used to rean pupae 133 plants. Duning most of the larval peniod the Ia::vae vlene not caged on the plants because they seldom moved fuom the plant on which they wene placed. Sunflowens were seeded each week in the gneenhouse to maintain a supply of suitable plants. Each larva was examined at 24 h inter"vals and r^econd.s were taken of the numben of molts. A cast skin, usually attached to the plant, r.¡as tÏ¡e rnain cniteníon fon detenmining that a molt had taken place. Changes in head capsule and body colou:r wene used as evidence of molting. La:rvae ín the cabinets at 15 and 20oC were tnansfenned to cages two days afte:: the thind molt while those in the 25o cabinet wene tnansfenned to cages one day after the thind molt. Circular" plastic cages, measuning 7 cm high by 10 cm wide with a scrìeened Iid, wene used to contain the maturing lanvae. In each cage a single two to for::r leaf sunflowen seedling þras transplanted into moist sifted sand. The sand pnovided a pupation site for. the beetles. The mean du::ation of the lanval peniod was based only on those índividuals sunvivíng to the adult stage. The dunatíon of each of the four. l-ar.val instars was affected by neaning tempenatune. At 15, 20 and 25oC, the sunflowen beetle requined an avenage of 36.6, 19.7, and 1-5.4 days, respectively, to complete Ianval development (Table 20). At 15, 20 and 25oC, the fir"st instar was eornpleted in 11.3,6.0 and 4.5 days, the second in 8.61 4.3 and 3.2 days, the thind in 8.6,4.8 and 3.6 days, and the founth in 8.1r 4.6 and 4.1 days, r:espectively. The finst-instan lanva thus nequined a mean of 30.2 pencent of the lanval developmental peniod whereas the second-, 134 Table 20. Developmental time (days) of larvae of the sunflowen beetle, Zygogramma exclamationis, at thnee temperatures. Tempenatune Dunation of lanval itr"l.o" l-dãj¡Ð,_ (J 1oC) 15 Mean 11. 3 8.6 8.6 8.1 36 .6 S.E. 0.4 o.2 0.2 0.2 0.6 Range 9-20 7-!2 7 -1-0 7-tt 32-45 N3030 30 30 30 20 Mean 6.0 4.3 4.8 4.6 1,9.7 0.1 0.1 0.1 0.1 0.2 Range 5-7 3-6 4-6 4-6 t8-22 N 33 33 33 33 25 Mean 4.5 J.Z 3.6 4.1 15.4 S.E'. 0.1 0.1 0.1 0.2 0.3 Range 4-6 2-5 3-4 3-8 73-2í- N 34 34 34 34 34 1Lt, Lz, L3, Lq = fir"st to fou::th larval instar, nespectively 135 thir"d-, and founth-insta:: lanvae requined 22,0, 23.8.and 24..0 per"cent, nespectívely (Table 21). Rogens (tgll) neponted that at 27 ! 2oC, the foun la::val instars of the sunflowen beetle were completed in 4.5, 3.5, 3.3 and 3.8 days, respectively, which repnesented 29.8, 23.2r 21.9, and 25.2 pencent of the total Iar.va1 period (15.1 days), nespeetively. The results reponted in Tables 20 and 21 a::e thus close to those ::eponted by Rogens (1977). Pencent montality fon the complete Lanval stage was 23.8, 15.0 and 12.5 fon the 15,20 and 25oC treatments, nespectively (tabte ZZ). Losses occu:rred during each instar., with the highest montality, 11.9 pencent, necorded for fou::th-instan lanvae at 15oC. Considening the mortality nates, the 20 and 25oc tneatments woul-d appearl to be in the optinal tempenatulre nange, while the 15oC t¡.eatment may be nea:r the lower critical tempenatur"e. Additional studies would be nequined fon verification. Rogens and Thompson (7978) neponted 22 pencent nortality dn:ring the larval stage when neaned at 26 ! 2oC on sunflowen Hybnid 896. In a laten papen Rogens and Thompson (1980) reported 20 percent montality duning the lanva1 stage when reared at 27 ! 2oC on the same hybnid. 4.1.6.4.2 Estímated ToLO and TU nequinements Results from the constant temperature ürial (Section 4.1.6.4.1, TabIe 20) wene used to estimate the lowen th:reshold temperatrre (folO) and the Theonetical thenmal unit (Theon. TU) nequinements fo:r the lanval stage of the sunflower beetle. An estimate of the ToLO was 136 Table 21. Total lanval development time and pencent of total Ia:rval developmental tine requined fon each of foun instar.s of the su¡rflowen beetle, Zygognamma exclamationis at thnee tempenatunes Total lanval Tempenatu::e developmental % totar developmental tíne by ínstanl (t 1oc) tíme (days) 15 36 .6 30 .9 23 .5 23.5 22 .t 20 t9 .7 30. s 27.8 24 .4 23 .4 25 15.4 29.2 20.8 23.4 26 .6 30 .2 22.0 23 .8 24 .0 'Lr, Lr, L3, L.¡ = finst to fourth lanval instan, r"çspectively l-J / Table 22. Pe::cent montalityr for each larval instan of the sunflower beetleo Zygognamma exclamationis, at thr"ee temperatur.es Tempenature Nurnber of Lanval instansz -a - (l 1-C)^ larvae Lr Lz Lo Lq Lr-L,. 15 42 7.r 2.4 2.4 11 .9 23.8 20 40 0 7.5 2.5 5.0 15 .0 25 40 2.3 0 1C ôc 12.5 r% r¡cntality based on initial numben of lar"vae 2Lt, Lt, Ls, L.. = finst to fourth lanval- instar", nespectively 138 requíl.ed fon the fonmula used to calculate TU accumulations. for the lanval stage in the field (Section 2.5.1.2). Theon. TUrs we::e calculated for" each lanval insta:: so that TU r"equirements in the labonatony could be companed to TU nequinements in the fíel-d (SectÍons 4.1.6.5.2 and 4.1.6.6.5). With a knowledge of the ToLO and TU nequinements, development of the lanval stage in the field can be descníhed and pnedicted. This has pnactÍeal applications, especially in improving the accuracy of the timing for insecticide applications ( Section 4 .1 .6 .7 .t) . An estimate of the ToLO for. each lanval- instan, and combinations of instans was calcul-ated using Annoldrs X-intercept method (fu:nold 1959) as outlíned in Sections 2.5.I.1 and 4.1.5.3. The estimate fon the Theon. TU nequinernents fon each instar" was calculated using the neg::ession equation for r.ate of development (Section 4.1.5.3). The estimated ToLOrs for the first-, second*, thir.d-, and j.nstar founth- lanvae wene B .1 , I .9 , 7 .5 and 3 .8oC, respectivel-y (fa¡te Z0). The estinated ToLO fon the finst- and second-instar periods combined was 8.4oC, a¡rd the TOLO fon the finst-, second- and thind-instan penÍods combined was 8.2oC. The estimated ToLO fon the complete lanval peniod was 7.3oC. The linear regression line (Cunve B) fon the ::ate of development for each lanval instan, as shown in Table 23, was plotted (Figune 15). The X-intercepts of Cur"ve B indicate the ToLOrs fon the respective stages. Cunve A of Figu::e 15 was calculated using the negression equations fr.om Tab1e 22 and solving fon Y (days nequir:ed fon 139 Table 23. Regnession equations, coqfficients of dete:rminationo estimated thneshotd temperatures (ToLO), and theonetical thenrnl unit (Theor. TU's) nequirements for development of lanvae of the sunflower beetle, Zygognamma exclamationis in dífferent instans and conbinatio CoefficÍent of Regnession equation 1 r 2 detenmination ToLO Theon .3 Instan (Y=a+bX) (n2) (oc) TUts L1 Y -0 .10670 + 0.01325X 0 .990 8.1 76 Lz Y -0,1762.3 + 0.01986X 0. 990 QO 50 L3 Y -0 . 1189 7 + 0.01596X 0 .994 7,5 63 La Y -0 . 0461 7 + 0.01210x 0. 896 3.8 83 LrLz Y -0.06700 + 0.00796x 0.990 8.4 126 L r-Lg Y -0 .04331 + 0.00532x 0 .991 oô 188 L r -L,* I -0.02746 + 0.00376x 0.980 7.3 266 1411 values rounded to five places. 2Y of number of days, X tempenatune oC. 3values=::eciprocal = in ane fnom the r"egnession equation r"ãunded to the neaï-est r¡rit. 140 Figure 15. Days nequired to complete development and nate of development of fí:nst-, second-, thind- and fourth-Ínstan ranvae of the sunflowen beetle, Zygograrrna excraniationis at constant ternpenatunes SECOND INSTAR 14 2 T'= 8.1'G .25 10 T'= 8.9'C Io T.U.'s = 76 T.U.'s 50 an o = o.laa i(t o 'å t'o (û \.,u 6ô à.rs ô .1 4.1 .05 THIRD INSTAR \ f'= 7.5"C T'= 3.8"C \ o T.U.'s = 63 r.u.'s =83 tt à.zo ô \.t .1 ï 28 74]- development) at each X (r"ea::ing tempenatu:re). Cu:rve A thus. is an estimate of the mean development time, in days, fon the respective lar"val instans at vanious constant tempenatunes. The estimated Theon. TU requinements for" the fir.st-, second-, third- and for::rth-instar larvae wene 76,50, 63 and 83, nespectíve1y, using TolOts of.8.1, 8.9, 7.5 and 3.8oC (ta¡fe Zg). The Theor-. TU nequi::ements fon the finst- and second-instar: peniods combined was 126 (e.+ toLO), and the Theon. TUts fon the finst-, second- and thind-instan periods combined was 188 (8.2 ToLO). The Theon. TUts requined fon the complete lanva1 stage was 266 using a ToLO of 7.3oC. 4.1.6.5 Lanval development duning field nearing During the summer"s of 1975 and !976, a total of thnee groups of sunflowen beetle lanvae wene t:eared outdoons in cages at Glenlea, Manitoba. The objectives of these neanings were finstly, to detenmine the duration of each of the four lanval- instans under outdoon conditions, and secondly, to estimate the TU requinements fon each instan. 0n JuIy 7, 1975, five newly-enenged l-anvae wene placed in sleeve cages on each of 10 sunflowen plants (cv. PenedovÍk). The cages wene tubes (cylindens) of fíne mesh screen about 30 cm long with a cloth sleeve attached to each end. The cloth at one end was gathened and tied around the sunflower" stalk while that on the other end was gathened and tied a-bove the gnowing point of the plant and suspended fuom a supponting stning. Usually, eveny second day, fi:om July 7 to July 27, 1975, the lanvae v¡ene r"emoved fi:orn the cageso reconds taken on sunvival , L42 and head capsu-l-e measu¡aements taken to deter.mine the instar. distnibution (Section 4.1.6.3). The lanvae wene netunned to the sleeve cages following exarn-ination. No substnate r^ras provided for the pnepupal on pupal stages. In 1976, 50 newly-hatched Ia::vae vrerle caged on seedling sunflowens (cv. Penedovik), at Glenlea, Manitoba, on each of June 10 and 11. Procedures l^iene similan to those descnibed fon the 1975 study except that the lanvae wene transfenned to lange scrleen cages (tZZ cn hígh x 91.4 cm x 91.4 cm) (figure 3d, p.57) within two days after: molting to the founth instan. Within these cages the lanvae had access to the soil and fo::med pupation chambens. TU accumulations wene calcul-ated oven the peniod of development of each of the thnee groups of field-near:ed lar"vae. The ToLO chosen to carculate the TUts was 8.4oc. This ToLo was serected because ít was the ToLO fon devel-opment of the fínst two instar"s combined (Table 22). The development of these finst two instar.s is most ímpontant firom a pnactícal víew because if this eanly development can be pnedicted, ínsecticide applications fon contr.ol of the lar-vae can be mone precisely timed (Section 4.1.6.7). The TUts fon each field-rea::ed gnoup were cal-culated cornmencing the day the lanvae ernenged fnorn the eggs in the respectíve groups. The method used to calculate the TUrs was the Chmiel-lIilson modification of the sevacherian et al method (section 2,5.r.2). Maximum and minimum daily ain temper-atune data wene obtained fnom weathen neconds taken at Glenlea by Agnicultr¡:re Canada. 143 4.1.6.5.1 Duration of the lar.val stage The duration of the first thnee lar"val instars of the sunflower" beet.l-e was estimated using data denÍved fnom the fietd-rea::ing study in 1975. Larvae in the second , third and founth instans were first noted in the field cages seven, 11 and 13 days, respectively, afte:: the group had hatched, while lanvae in the finst , second , and thind instars v¡ene Iast noted after seven, 13 and 15 days, respectively (ta¡te Zt+). The estirnted time nequined to eomplete development to the end of the finst , second and thind instans was thus in the range of six to eight, 10 to 14, and 72 to 16 days, nespectively. One day was added to each end of the r"ange because the lanvae weue cheeked only eveny second day. In the field study, in 1975, the dunatíon of the fou:nth instar could not be estÍmated because the initiation of the pnepupal stage was not accunately deter.mined for. atl individual-s. Since thene is no rnolt to the pnepupal stage, behaviounal changeso such as cessation of feeding and enter:ing soil to fo::m a pupation chamben, have to used to irrdicate the beginning of the pnepupal stage. Howeven, soil on any othen suítable mater"ial- was not pnovided in the cages used in 1975, thus a change in feedíng behavioun llas the only indicator that could be used to detenmine when the larvae had completed the founth instan. on day 21, seven of 30 l-ar-vae were noted at the bottom of the sleeve cage, appanently having completed feeding pr"ion to pupation (Table 2t+). The day on which alr rar-vae had changed feedÍng behavioun (i.e. the last day a founth-instan lanva was pnesent) i^ras not known. Development was appanently affected by the lack of a pupation site. A few individuals 144 Table 24. Developrnent of lanvae of the sunflowen beetle, Zygognamma exclamationis, in cages at Glenlea, Manitoba, Jilffi-77, 19 75 Expeniment Numben of 9o in instar"3 dayl TUrsz lanvae E Lz Ls L¿r 1, 16 L00 .0 0.0 0.0 0.0 2 25 'j e 34 4 39 5 45 4ì rão.o ã.0 ã.0 ã.0 6 54 7 67 3B 26.3 73.7 0.0 0.0 I B3 I 100 ; 0.0 roã.0 ã.0 o.o 10 119 tt 137 37 0.0 13.s 86 .5 0.0 t2 151 13 163 3; 0.0 ,.n g+. s i.n 14 174 15 185 32 0.0 0.0 34 .4 65.6 16 195 77 207 ; 0.0 ã.0 ã.0 roo.o 1B 276 19 228 ; 0.0 0.0 0.0 100.0 20 242 27 253 304 0.0 ã.0 ã.0 roã .0 llanvae hatched on the aftennoon of July 6 (Day 0) and wene caged outdoons on the monning of rluly 7, 1975 (Day 1). 2Ther"mal units carculated using a B.4oc lowe:: thneshold tempenatune. t", L3 and L,+ finst- to fou:rth-insta:: nespeciívety. ?L.t,aseven = larvae, of 30 lanvae noted. Ín bottom of cage, appanently ieanching for" a pupation site. 145 molted to the pupar stage and subsequently died on became deformed adults. The majonity of the indivíduals failed to molt to the pupat stage and eventually died. The du:ration of the finst thnee lanva1 ínstans was estímated. using data fuom the two gnoups of Iár"vae near:ed in f iel-d cages in 1976. rn the finst field study in 1976, rar.vae ín the second , thind and founth j.nstans wene finst noted six, 13 and 19 days, ::espectíve1y, aften the gnoup had hatched, whire lanvae in the finst , second and thind instans wene last noted aften nine, 13 and 21 days, nespectívely (fa¡te ZS ). The estimated time nequined to complete development to the end of the finst , second and thi¡.d insta:rs was thus in the nange of five to 10, t2 to 14 and 18 to 22 days, nespectively. similanly Ín the second field study in 1976, the estÍmated time ::equíned to complete development to the end of the finst , second and third instans was in the nange of nine to 11, 13 to 15 and 19 to 21 days, nespectively (ra¡te zo). The dunation of the founth larval instar" was difficul-t to estimate for" the 1976 field studies because the initiation of the prepupal- stage was not definítery known. Although soÍl was pnovided fon pupatíon, Ít was dÍfficult to determine when the fír.st founth-instan lanva had left the plant and entered the soil-. Reductions in the numben of lanvae on the plants four on mone days aften for:::th-instan lar:vae wene first noted, were assumed to be due to 1anvae leaving to fonm pupation chambens. Reductions, howeven, may have been due to pnedation o:: othen causes. I^lith the above assumption, development 146 Table 25. Developmqnt of lanvae of the sunflowen beette , zygo+rawna exclamationis, in cages at Gl_enlea, Manitoba, Junõ-10 to July B, 1976 Expeniment Numben of % in instar3 day 1 TUr s2 lanvae L1 Lz Le La t 13 25 100 .0 0.0 0.0 0.0 2 25 ,: 100 .0 0.0 0.0 0.0 o 3B 4 47 5 54 6 57 ; ãu.u i.u 0.0 ã.0 60 2t 85 .7 14.3 0.0 0.0 I 65 I 69 77 sB.9 b1 c 0.0 0.0 10 76 tt B9 ; 0.0 roã .0 ã.0 ã.0 t2 1-02 13 ttt 13 0.0 92 .3 7.7 0.0 14 t2B 15 138 ; 0.0 ã.0 roã. o o.o 16 147 t7 154 T2 0.0 0.0 100 .0 0.0 18 161 19 t67 * 0.0 o.o zi.o zs.o 20 175 2t 184 12 0.0 0.0 i.6.7 83.3 22 194 23 206 ;" 0.0 ã.0 o.o roo.o 24 219 25 23! 4a 0.0 0.0 0 .0 100 .0 26 246 '!4 27 259 0.0 ã.0 0.0 100.0 28 271 29 284 04 0.0 0.0 ã.0 ã .0 llanvae hatched on the aftennoon of June 9 (Day 0) and wene caged. outdoor"s on the monning of June 10, 1976 (Day zThe¡mal 1). units calculated using a 8.4oc rowen threshold temperature. nr, L3 and L¿+ finst- to founth-instan ?L,r,4Reduction = lanvae, respeciivety. in numben of lanvae on plants assumed to have been d.ue to pupation. 147 Table 26. Development of la:rr¡ae of the sunflowen beetle, Zygognarum ffi.exclanrationis, in cages at Glenlea, Manitoba, June 11 to .Hxperr-ment Numben of 9o in Ínstan3 dav 1 ! 72 ,: 100 .0 0.0 0.0 0.0 2 25 õ J 34 4 41 5 44 It 100. 0 ã.0 ã.0 ã.0 6 47 20 100.0 0.0 0.0 0.0 7 52 I 56 13 100 .0 0.0 0.0 0.0 I 64 10 76 t uo.o oo.o ã.0 ã.0 77 B9 t2 98 I 0.0 100 .0 0.0 0.0 13 tt2 -7 14 t2s 0.0 ze.a ti.+ ã.0 15 134 16 141 6 0.0 0.0 100 .0 0.0 t7 148 1B 155 ; 0.0 ã.0 1-oo.o o.o 19 t62 20 t7t 5 0.0 0.0 40.0 60 .0 2t L81 22 193 ;* 0.0 o.o 0 .0 100 .0 23 206 24 2tB 25 0.0 0.0 0.0 1_00.0 25 233 q 26 246 7- 0.0 ã.0 ã.0 .oã.0 27 258 -t 28 27t 0.0 0.0 0.0 100.0 29 286 E 30 300 0' 0.0 ã.0 o.o o.o 1l,"orr." hatched on the afternoon of June 10 (Day 0) and were caged ^outdoor"s on the morning of, June 11 (Day 1). lrrrenrnar units calculated using a B.4oc-towår thneshold temperature. i,Lr, L", L3 and L,+ = finst- to fou:rth-instan Lanvaer l?espectively. lReduction in numben of lanvae on plants may have been due to pupation. "Reduction in nu¡nben of lanvae on plants assumed to have been d.ue to pupation. 148 time to the end of the founth instar was in the nange of 22.to 28 and 23 to 29 days, nespectÍvely, for the first and second field studies in 1976. Using the results fnom all thnee field studies, the mean time requi::ed to complete development to the end of the finst , second and thirnd instar"s was in the nange of 6. 7 to g .7 , 71.7 to 14. 3 and 16 .3 to 19.7 days, nespectívely. using data fr"om the 1976 studíes, the number of days requined to complete all foun instans was less confiderrtly estimated to be in the nange of 22.5 to 28.5. 4.1.6.5.2 Estimated TU nequinements Estimates of the TU nequinements (4.+oC ToLO) to complete each of the foun larval instans of the sunflowen beetle wer:e mad.e using data fnom the 1975 and 1976 field tr"ials (Sectíon 4.1.6.5"1). In the 1975 field tnial, the estimated numben of days nequined to complete development to the end of the fi.nst , second and thind instars was in the::ange of six to eight, 10 to 14 and 72 to 16, r"espectively, which was 54 to 83, 119 to 174 and 151 to 195 TUrs, nespectivery (Table 24). similar'lyo fon the finst field tr"ial, in 1g76, the estimated number of TUrs nequired to complete development to the end of the first , second and thind instans was 54 to 76' !02 to 125, and 154 to 194, nespectively (tabte 25), whíle the TU r.equinements irr the second field ü:ial in 1g76 was 64 to 89 , 772 to 134 and 162 to 18i-, respectively (ta¡te ZO). Using the estimates from all th::ee tniaLs, the mean range of TU nequinements to the completion of the first , second and thind instar.s 149 was 57 to 83, ltt to 144 and 156 to 190, nespectively. rn.labonatory studies (Section 4.1.6.4.2) the mean TU r.equirement fon the completíon of the finst two, and finst thnee lanval- instans was 126 and 1BB, respectívely. These laten values are very close to or within the nanges shown above. 4.1.6.6 Lanval development in sampling plots in commencial sunflowen fields 1975 to 1977 The develoPment of lanvae of the sunflower beetle in the field was followed by noutine sampling in commercial sr:nflowen fields du:ring the summens of tg75, 1976 and tg77 . One site was selected at Ste. ,Jean in 1975, one at Letellien ín !976, and one each at ste. Jean and. Lowe Farm in !977. Twice pen week lanvae v,rere nemoved fnom plants in subplots taken at nandom. The larvae were pnesenved, and later:, the head capsules wene measuned to detenmíne the pnoportion of the lanvae in the r"espective instans. Details on natenials and method.s are found ín Section 3.4. 4.1.6.6.1 Ste. Jean, tg75 The first commercial sunflor¿en field to be sampled routÍne1y was at Ste. Jean, Munitobu, in 1975. Sunftowen beetle l-anvae wene finst noted in the samplíng plot on June 17, 797s, all lanvae being in the finst-insta:r (Table 27). Lanvae in the second. , thind and for::rth instans wene finst noted in the plot on June 24, June 27 anð. Jury 1, nespectÍvery, which was seven, 10 and 14 days, nespectively, after. the finst larvae wer.e found. Table 27. Nunber of eggs, lanvae and adults of the sunflowen beetle, Zygog:ramrna exclamationis, necorded on sunfl-ower plants in a sampling plot in a comerciar tietã-ãffi.rean;-M-ánffi'ba-, tgTs Numben of Number of _ Numben of lanr¡ae/p1ant3 Nurber. of Sanpling plants eggs/plant L r Lz tg t¿+ L r:L+ adults/plant date TUts1 sampled2 meaffi; Mean Mean Mean Mean Meãã-S.E. -ïú'ean- Jure 13 259 119 6.48 0 .47 0 0 0 0 0 0 .18 June 17 286 t22 10.86 0.75 0 .29 0 0 0 0.29 o.oe 0 .18 Jtme 20 320 122 10.59 0 .66 1.28 0 0 0 1,28 0.19 0.29 June 24 373 t24 3.20 0 .32 1.98 0.27 0 0 2.19 0.21 0.72 June 27 415 66 3.59 0.52 3. 38 I.72 0.06 0 4 .56 0 .38 0. 15 July 7 468 t02 !.27 0 . 19 2,86 1 .68 0.26 0.01 4 .81 0.42 0 .09 JuJ-y 4 508 tt6 0.74 0.09 1.92 1.64 0 .57 0 .10 4.22 0.27 0 .08 JuJ-y I 564 103 0 .91 0 .19 2.34 2.tt 1.52 0.40 6.37 0.44 0 .04 JuIy 11 586 103 0 .54 0 .12 1 .84 1.92 I OC 0.93 6 .54 0.46 0.03 July 15 641 tt2 0.29 0.r2 0.37 1 .83 1.98 1 .99 6 .16 0.43 0.02 Juty 18 692 t29 0.08 0.02 0.33 1.01 2.!0 2.16 5 .60 0.35 0 .01 JuIy 22 739 t2t 0- 0.12 0 .44 ñoo 1.65 3.20 0.24 0.01 lThenmal units (TUts) calculated using B.4oC as the lower thr"eshol-d tempenatulîe, starting on Ap::il t) 1975, and using daily ain tempenature data f::om the Moruis Vleather Station. 2Sunflowen cv. lÕ:asnodanets. 3Lrr'Le, Lg, and Lq = first-, second-, thir"d- and founth-instan larvae, ltespectivel¡,. Þ oCN 151 Lanval populatíons ín the ste. Jean plots peaked at.6.5 lanvae pen plant on July 11, 1975 (taUre zz). The maximum numben of fir.st-, second-, thind- and founth-instan lanvae per prant was recorded on June 27' Jury 8, July 18 and July 18, nespectively, with values of 3.4, 2.7,2.1 and 2.2. The mean numben of first-, second-, thind- and fourth-insta:: lanvae per prant on each samplíng date is pnesented gnaphically in Figune 16. The mean numben of lanvae pen plant was divíded in half and plotted on eithen side of zero to pnod.uce a tballoontr-type figune . Sampling at the Ste. Jean plot was prematurely tenrninated on Jt:ry 22 due to an accidental application of insecticide by the cooperaton on July 23. The date when lanval devel_opment wou]_d have been completed was thus not detenmined. 4 .t .6 .6 .2 Letellien, 19 76 rn 1976, a sampling plot was set up at LeteLlie:r, Manitoba. Lanvae wene finst noted in the plot on June 1s, 1976, all ranvae being in the fÍnst instan (ta¡fe ZS). Lanvae in the second , thind and fou:rth instans were first noted Ín the plot on June 19, Jrme 22 anð. July 29, nespectively, which was thnee, seven and 14 days, respectivery, aften the finst lanvae wene found. The lanval popuration in the Letelrien plot peãt.d at 3.7 Ia::vae pen plant on July 16, 1976 (Table 28). The maximum numben of finst-, second-, thind- and fourth-instan lar"vae pen plant was neconded on June 29, July 6, Jury 13 and July 16, nespectively, with ]-52 Figune 16. Development of lanvae of the sunflowen beetl-e, Zygograrnma exclamationis, Ste. Jean, Manitoba, I1TS qt!-e_r- oJ !,1-q _ -L-a-r_v_a-e_ lst lnsta r,/plant 2nd Instar./Plant 3rd Instay'Plant ¿th lnstarr/Plant o Ol\)O Þ L o tr o t c o 3 õ= o CL { :t ort J o- CN c c Ø=. @ 5. o {" t- o Table 28. Nrrmben of eggs, Iarvae and adul-ts of the sunflower beetle, Zygogramr¡a exclanationís, recorded onsunf1oweiPiantsinasamplingptotinacomrnercÍa1fiel@,tgzo l3 Sampling plants eggs/plant adults/ptant date TUr sr ga lGan S.E. Mean Jure 4 266 109 2.1.9 0.30 0 0 00 0- 0.03 Jrne B 319 79 1.63 0.20 0 0 o0 0- 0 .05 Jrme 11 360 72 2.33 o.27 0 0 00 0- o.t7 .Iune 15 39q 55 3 .89 0.46 0.11 0 00 0.11 0.05 0 .11 .Iure 18 410 62 3 .79 0 .38 0.05 0.08 00 0.13 0.07 0..16 Jtme 2-2 453 58 5 .47 0.54 0.32 0.28 0.08 0 c .69 0.14 0.03 Jurre 25 490 62 4.32 0.51 0.76 0.10 0 .05 0 0.92 0 .27 0.13 Jur¡e 29 520 67 2.58 0.41 1.26 0 .13 o.2i 0.05 t.72 0.23 0.19 July 2 552 68 !,74 o.29 1.1r+ o.23 0.11 0.02 1.50 0,2tr 0. 16 .Iuly 6 607 65 . 0.25 0.0? o.6q 7.28 0.42 0.08 2.42 0.30 0.1.2 .Ittly I 648 67 0.10 0.05 0.60 0.61 0. 75 0.15 2 .72 0 .30 0.03 July 13 695 63 0 - o,29 0.. lr2 1.23 I .08 3.02 0.39 0 JuIy 16 722 80 0 - 0.06 0. 7lt t.2t 1.67 3.68 0 .38 0 July 20 772 56 0 -o 0.19 0.38 1. s1 2.09 0.28 0 .Iuly 23 808 7\ o -0 0.01 0 .20 0.37 0.58 0 .72 0 ,Iuly 27 860 53 0 -0 0 0 ,0r+ 0 .26 0.30 0.09 0 .Iuly 30 891 59 0 -0 0 0.02 0.20 0 .22 0.06 0.034 Aug. 3 931 tl4 0 -0 r) 0 0.07 0.07 0.0r+ 0.02 Âug. 6 961 89 0 -0 0 0 0. 04 0.0r+ 0.03 0 .01 Aug. 10 1010 56 0 -0 0 0 0 0- 0. 04 Aug. 13 104r+ 78 0 -0 0 0 0 0- 0, 09 Aug. 17 1092 58 0 -0 o 0 0 0- 0 .09 Aug. 20 1143 52 0 -0000 0- 0.10 Aug. 2¡+ 1200 67 0 -0000 0- 0.08 Aug. 27 7247 54 0 -0000 0- 0 .07 Aug. 31 1264 63 0 -0000 0- 0 .03 Sept. 3 1285 6q 0 -0000 0- 0.05 Sept. 7 1334 65 0 -000c 0- 0.03 Sept.10 1351 68 0 -0000 0- 0.01 Sept.14 1383 63 0 -0000 0- 0.03 Sept.17 14C6 67 0 -o000 0- 0 lThermal units (TU's) calculated usi¡g 8.4oC as the loù'er threshold temperature, starting on Âpril 1, 1976, and using daily air ternperatu¡e Cata fro¡n the üorris Heather Stãtion. zSunfLower cv. Krasnodar.ets 3Lt, Lz, L3, ãnd to = fÍrstr seeond, thírd and fourth instar larvae, respectively, qAIl adul,ts collected on,July 30 and laten were ¡qç-gpner'ation beetles. F U1 C¡) 154 varues of 1.3r !.3, t.2 and !.7. The mean numbe:: of finst-., second-, thind- and founth-instan lar.vae pen plant on each sampling date is pnesented graphically in Figune 17. The last lar"r¡ae were neconded in the Letellien plot on August 6, 1976.. which was 52 days on 567 TUts (g.4oc ToLO) aften the finst la:rvae wenê noted. 4.1.6.6.3 Ste. Jean,' 1977 fn 1977, a sarnpling p10t was set up at ste. Jeano Manitoba to follow the development of lanvae of the sunflowen beetre. The spning of 1977 had been war"men than usual, thus the sunflor^rers ín this field had been seeded eanlien and emenged at an eanlien date than did those in the 1975 and 1976 sarnpling plots. The fÍnst lanvae wene noted in the plot on May 31, 1977, both finst-, and second-instan ra::vae being necovened (ta¡te zs ). Lar:vae in the thínd and for:rth instans wene finst noted in the plot on June 7 and June 17, nespectively, which was seven and 17 days, nespectively, aften the fínst l-anvae were found. rn 7977 o the lanval popuration in the ste. Jean plot peaked at 7.2 l.anvae perl plant on both June 21 and 24 (ta¡te Zg). The maximum nr¡nben of fínst-, second-, thÍnd- and founth-insta:: ranvae pen plant was necol3ded on June 10, ilune 21, June 24 and June 28, nespectively, with values of 4.4, 3.0r 2.4 and 1.s. The mean numben of fi::st-, second-, thind- and founth-instan lanvae pen plant on each sampling date is pnesented gr:aphically ín Figune 18. he last lanvae wene reco::ded in the ste. Jean plot on Jury 19, !977, which was 49 days on 479 TUts (9.4o ToLO) aften the finst lanvae wene noted. 155 Figu::e 17. Development of lanvae of the sunflowen beetle, Z,ygograrma exclgnationis, Lete1lier, Manitoba, Lg76 o.75 c G o- ìo (t 5 til o,75 c s À \o or G :i 5laD Ì¡l ji r,l I ol o.751 Ll c S! o f' õ zi=! \o o cU, !t ta.r g o õ \ o o c g, I o. 600 700 90 Accumulated Thermal Units (e.¿C T'LO, Table 29. Numbe:: of eggs, larvae and adults of the sunflowq: beetle, Zygognannn exclamationis, neconded 'onsunf1owenp1antsinasamp1ingp1otinacommencia1rier,1'g77 Numben o Sampling plants eggs/P1a¡rt adu].ts/plant date TUrsl sampled2 Mean S.E. Mean Mean Mean Mean Mean May 25 342 50 7 .28 0 .7s 0 0 0 0 0 0 .38 I'[ay 27 369 50 7 .24 0 .96 0 0 0 0 0 0 .34 May 31 402 100 4 .20 0.44 0. 31 0.05 0 0 0.36 0.12 0 .10 June 3 424 100 4 .27 0 .39 0 .15 0 .09 0 0 0 .24 0. 11 0.10 June 7 453 100 2.68 0.30 2.72 0.23 0.01 0 2.37 0.28 0.09 June 10 469 75 3.19 0.34 4.38 0.72 0 .15 0 5 .25 0.49 ,June 14 493 101 7.tt 0 .23 2.62 1.83 0.tt 0 4.56 0.3s 0 .03 June 17 522 45 0.67 0 .15 1.98 1.98 0.62 0 .05 4 .62 0 .51 June 21 555 100 0 .20 0.11 1. 90 3.02 2,14 0 .18 7 .23 0.57 o.or June 24 590 100 0.22 0.09 1. 63 2.53 2.39 0.68 7 .23 0 .52 0.02 'June 28 638 100 0- 0.88 ¿.!l 2.tt 7.47 6.64 0.44 0 Jufy L 659 100 0.08 0.08 0 .25 1.69 2.27 1.41 5.56 0.40 0 July 5 710 100 0- 0.07 0.36 0 .80 1.18 2.41 0.23 0.01 JuJ-y I 747 100 0- 0 0 .05 0.74 1 .31 2 .10 0 .18 0 July 12 790 100 0- 0 0 .01 0.08 0.44 0.53 0.09 0 ,JuIy 15 82t 100 0- 0 0 0.01 0 .11 0.!2 0.04 0 July 19 881 100 0- 0 0 .02 0 0.02 0.03 0 .02 0.044 JuIy 22 913 100 0- 0 0 0 0 0- 0.02 JuJ-y 26 957 100 0- 0 0 0 0 0- 0,02 July 29 988 100 0- 0 n 0 0 0- 0 Aug. 2 to28 100 0- 0 0 0 0 0- 0 Aug. 5 10s1 100 0- 0 0 0 0 0- 0 lThennal units (TUts) calcul-ated using a g.4oC 1ower thneshold tempenatu:re, starting on Apnil 1, 7977, and using daily ain tempenature data fnorn the Monnis lleathe:: Station. 2sunflowen cv. Sundak. tLt, Lr, L3 and L4 finst-r second-, third- and fomth-instan 4A11 = lar.vae, t:espectively. adutts collected on July 19 and later brere new-gener.ation beetles. (,Þ o) 157 Figune 18. Development of larvae of the sunfrowe:: beetle, Zygogranna exclamat_ionis, Ste. Jean, Manitoba, !977 2 E o o.- \ Ëo 1H (t, s s -st c o d \ o Ëi (t, >r s ä: t, J¡ CÐ I Or L¡ si c Ft o 5r À \ zi (U Dt-. +. sØ It c(\l Fc o À \^ (ú (, ù. v, s +.6 400 500 600 o Accumulated Thermal Units (4.¿'C T=LO) 158 4.1.6.6.4 Lowe Fanm, tg77 The second sanpling plot set up, in tgi7, was at Lowe Fanm, Manitoba. This fierd had been seeded laten than the ste. Jean plot, thus, the development of the cnop and the sunflowen beetle was somewhat behind that of the Ste. Jean ptot. The fínst Ia:rvae wer.e noted. in the plot on June 7, 1977, a1l lanvae being Ín the finst instan (fa¡te gO). Lanvae in the second , thind and founth instan wene finst noted on 'June 17' June 24 and.Tuly 1, r.espectivery, which was 10, 17 and 24 days, nespectively, aften the finst lanvae wene found in the prot. The larval populatiorr in the Lowe Fanm plot peaked at 13.4 lanvae pen prant on June 28. 1977. The maximum numben of first-, second-, third- and founth-instan lan¡ae per plant was rlecorded on June 28, June 28, July 5 and July 12, nespectivelyo with values of 6.2, 5.0,4.0 and 3.3 (Table 30). The mean numben of finst-, second-, thind- and fourth-instan lar"vae on each sampring date is pnesented gnaphically in Figune 19. The last lanvae wene recor"ded in the Lowe Fanm plot on July 2g, 1977, which was 52 days on 535 TUts (8.4o ToLO) aften the finst l_anvae wene noted. 4.1.6.6.5 Dunation of the lanval stage and estimated TU nequir.ements The peniod between fÍnst and rast appeanance of lanvae vras estimated using data fuom the 1976 and.1977 sampling prots (Tables 28 to 30). The mean date of fir"st obsenvation of lanvae in the sampling plots was Jr:ne 7I^¡íth a corresponding ¡nean TU accumulatíon (B.4oC ToLO) Table 30' Numbe:: of eggsr larvae and adults of the sunflowe:r beetle, Zygog¡anrna onsunf1owerp1antSinasamp1ingpI.otinacommencia1fie1,rcll exclarnationis, neeonded umben o of lar:vae Sampling plants eggs/plant 1 2 3 L4 adults/plant date TUtsl led2 Mean S.E. Mean Mean Mean Mean Mean Jr¡re 3 424 100 5 .88 0.43 0 0 0 0 0 0.41 June 7 453 100 6.17 0. 51 0 .01 0 0 0 0. 01 olor 0 .13 Jr:r¡e 10 469 tot 5.34 0.59 0 .16 0 0 0 0. 16 0 .05 June 14 493 92 7 .71 0.72 0.93 U 0 0 0.93 0. 13 0.2! June 17 522 76 5.20 0.66 1.78 0.04 0 0 1,.82 0.21 June 21 555 96 3. 65 0.40 3. 56 0. 48 0 0 4 .04 0.36 olos lTune 24 590 tt2 2.68 0.32 4.7! 2.12 0.13 0 6.96 0.44 0. 06 June 28 638 77 2.19 0 .33 6. 18 4 .98 2.28 0 13.44 t.2t 0 .05 .Iuty ! 659 96 1.04 0 .21 3 .96 3. 59 3 .06 0.14 10. 75 0.68 0.06 July 5 710 89 0- 1.34 2.92 4.63 1 .58 10. 46 0.80 0 JuJ-y A 747 104 0. 14 0. 06 1. 08 1 .49 3.08 2.!2 7 .77 0 .59 0.03 .Tuly 12 790 116 0- 0. 30 1.02 2.03 3 .28 6,62 0.41 0 tluty 15 827 104 0- 0 .10 0 .64 1.47 2.80 5 .01 0.37 0 19 881_ 62 'July U- 0. 02 0 .11 7.26 2.44 3.82 0 .37 0 July 22 913 B7 0- 0 0 .07 0 .51 0 .86 1.44 0 .18 0 ,JuJ-y 26 9s7 69 0- 0 0 0 .10 0.77 0. 87 0 .14 0 July 29 988 94 0- 0 0 0 0. 18 0 .18 0 .0s 0.034 Aug. 2 1028 84 0- 0 0 0 0 0 0.!7 Aug. 5 10 s1 59 0- 0 0 0 0 0 0.51 Aug. I 10 86 110 0- 0 0 0 0 0 0.71 Aug. t2 1105 75 0- 0 0 0 0 0 0. 76 Aug. 16 M7 89 U- 0 0 0 0 0 0. 11 Aug. 19 1144 79 0- 0 U 0 0 0 0.27 Aug. 23 1 166 116 0- 0 0 0 0 0 0.12 rTherTnal (TUts) units calculated using B.4oc as the lower^ thr.eshold tempenatureo star:ting on ep*i, .!.'l?77, and using daily ain tempenatune data fuom the Monnis weather Station. -5unfl_or^rer cv. Knasnodanets L=' L3, and La fi::st, second, "L'r,aAll = thÍr.d and founth instar. lar:vae, respectívely. Þ adults collected on (n Juiy 29 and laten were new gener.ation beetles. (O L60 Figune 19. Development of lanvae of the su¡flower beetleo Zygognanrna excLamationis, Lowe Fanm, Manitoba, tg77 Ê o f, (!, s -.t 3 É ol o' o! añ i: E T'L. 5i c) o: L-l or gr (Itc E: q zifr go !t ÎN c ¡.-g \ g Ø 500 600 800 Accumulated Thermal Units (e.¿þ T.LO) June 161 of 416 (faUte gt). The mean date of last obsenvation was JuIy 28 vrith a mean TU accumulatíon of 943. Lanvae wene thus pr"esent in the sampling plots fon a mean of 51 days (nange, 49 to 52) on 527 TUrs (r:ange, 47g to 567). The 1975 plot at Ste. Jean was not used in estimating thÍs peniod because sarnpling had been pnematunery terminated (section 4.1.6.6.1). An estimate of the numben of days and TUrs nequired to complete each of the finst thnee lanval instans was made using d.ata fuom the four sampling plots (Tables 27 to 30). A modífication of the method of Taylon (fs3o) was used, wheneby an estimate of the du¡ratíon of a given stage was determined by calculating the peniod between the date when 50 pencent of the total obsenved population in a given stage !,Ias obser"ved to the date when 50 percent of the totar popuJ-ation was obse::ved in the next stage. This s0 percent val-ue will, heneafter, be nefenned to as the development time fo:: 50 pencent of the cohont or: the DTso. The DT56 fon each lanval instan was cal-cul-ated in the following manner. Finst, fon each sampling date, the mean numben of lanvae per plant r+as added to previous counts to establish a cumulative count. Fo:: example, ín 1977, at Lowe Fa:rm (Table 30), the cumulative count for fir"st-instan lar"vae on June 7 was 0.01, on June 10 was 0.01 + 0.16 = 0.r7, and so on untíl July 19 when the last fir.st-instar larva was collected (cumulative count = 24.13). The values calculated for each sampling d.ate wene convented. to a pencentage cumulative count. Fon exampre, on Jr:ne 7 the percentage cumuratíve count *as d#x 100 = 0.04 pencent; ñ 1'7 on June 10 was ãffi x 100 = 0.70 pencent; and so on untir Jury 19 when 762 Tabre 31. calenda:r date and accumulated therrnl units, (rurs) at finst and last obsenvation of l-ar"vae of the sunflowen beetre, Zygog::am¡rn exclamationis, ín thnee sarnplíng prots in s outhãET¡tanjGlS'7õ:i s z z Finst obse Last obsenved 0bsenvat rs. Samplin t TU Dãte -,mã Davs TUrs LetellÍen, 7976 June 15 394 Aug. 6 961 52 567 Ste. Jean, 1977 May 31 402 JuJ-y 19 881 +9 479 Lowe Fanm, 7977 June 7 453 July 29 9BB 52 535 Ju:e 7 416 July 28 943 51 527 lThennal uníts calculated usíng 8.4oC as the lowen thneshold tempenatu:ne, starting on Apníl 1 of the coruespondíng yean, and using daily air" tempenature data fuom the Monnis Weather Statíon. 163 the pencentage cumulatíve count *a" ## x 100 = 100 pencent. A linea¡ regnession l-ine was then calculated fon the centen pontion (709o < y < g0%) of the nesulting sigmoid curlve where x = accumulated TU's (B.4oc roLO) since Apnir'1, and Y = pencent cumulative count. The DT56 fon the first-instar popul-ation was then calculated by solving the equation for Y = 50. Fon examplê, the l-inean negnessíon equation fon the finst- Ínstan population in the 1977 plot at Lowe Fanm was Y = -277.90 + 0.552X with ne = 0.996. solving for y - 50, X = 59s. The DT5g for: the finst- instan lanvae in the Lowe Fanm plot uas thus 595 TUts which conr"esponded to June 25, 1577. The accumulated TUrs and connespondíng calendan date at DT5g fon each i¡:,stan in the foun sampling plots ís presented in Table 32. The DT59 fon the thírd- and fou::th-instar. lanvae in the 1975 pÌot was not calculated because samplíng had tenminated befone develop- ment was complete. The estimated nurnber of TUts and days nequi::ed to complete development of the fir"st thnee ]-anval instar.s of the sunflower beetle was calcurated fnom the data pnesented in Tabre 32. Fo:: example, the estimated numben of TUrs nequined to complete deveropment of the first instan in the !977 Lowe Fanm plot was the diffenence between the DT56 of the fÍnst-instan lar"vae and the DT5g of the second-instal: lanvae, that is, 650 - 595 = 55 TUrs. SimÍlar.ly the numben of days nequined was June 30 to 'June 25 = five days. The estimates fon each of the finst three instans is shown in Table 33. The r:equinements of ranvae in the founth instan could not be calcul-ated because the DT5g for the pnepupal stage was not known. Routine sampring fon prepupae 164 Table 32. Accumul-ated rutsl and cor^responding dates fo¡: the DT5g2 of the fou:r instans and the complete lanval peniod of the sunflower beetle, Zygognamma exclamationiq, at four sampling ptots in south-cenffioEæ:GÐ. TU?S Ste. Jean, 19 75 450 534 Letellien, 19 76 530 613 oáz 726 oão Ste. Jean, 1977 492 554 598 661 557 !gyg-Igtt¿ 1977 595 650 717 79i- 672 ------65 -- -116-- - -- Mean 517 s 6B 7------612- - Date Ste. Jean , 1975 June 30 July 6 Letellien,, 1976 JuIy 1 JuJ-y 7 Juty 10 July 17 Juty 9 Ste. Jean, 1977 June 14 June 21 June 25 July 2 Jvne 22 lgye_Iergz_!s_72______{gle_?I__{gle_99____{sly_q_Mean ---Jñe-ã5--Jü1t-i-----Jürt-[-----Jurt-if----j"li-f- _ ruly 13 ruJ_y 3 lTuts = thenmal units caLculated r,¡ith B.4oc as the lowe:: thneshold ^temperature, commencing Apnil 1 of the comespondíng year.. 'DT50 = development time fo:: 50% of cohont. "L'r, Lr, L3 and L.r = finst- to forrth-instar: lanvae, nespectively. 165 Tabl-e 33. Estimatedl nunùen of TUts2 a¡ld days nequir"ed to complete development of the fÍnst thnee lanval instans of the sunflowen beetle, 4ygggqnqna exclamationis, in fou:: sampling plots in g7S-Ig77. TUts Ste. Jean, 1975 B4 Letellien,- 1976 B3 49 64 1-32 196 Ste. Jean , 7977 62 44 63 106 169 !ere-Icrr ¿-!9ZZ___-_____t9______91______99______11q______199__ Mean 7 t --51------6-0------î18------Is7-- Days Ste. Jean , 1975 6 _ Letellien, 1976 6 916 Ste. rlean , 7977 7 4 7tt 18 lEstinated by DT59 DT5g method, modified from (1990). 2TUts - Taylo:: = thenmal units calculated with an B.4oC lowe:: threshold tempenature. 3Lt, Lz: Lg a¡¡d Lq = finst- to founth-instan lanvae, nespectively. . 166 had not been done in nrany of the sampling plots As presented in Table 33, the mean number" of TUts (B.4oC ToLO) r"equir:ed to comprete devel-opment of the first ínstan was 71 with a lrange of 55 to 84. The second and thir"d instans requíned 51 (range, 44 to 61) and 69 (nange, 64 to 80) TUfs, nespectively. The first two insta:rs combined nequined 118 (r"ange, 106 to 192) TUrs and. the finst thnee instar"s combined nequined 187 (nange, 169 to 196) TUts. As detenmined ín the labonatony (Section 4.1.6.4.2) the Theor.etical TUts requined fon development of the finst two, and finst thnee instans combined was 126 and 1B8o r:espectively (tabte z3), which is veny close to the estimates of 118 and 187 presented above. Using the DT56 to DT5g method pnesented above, the mean numben of days nequined to complete the fir"st instan Ín the sampling pl-ots was six with a range of five to seven (tabfe gg). The mean numben of days nequíned for: the second and thir"d instans was 5.3 (nange, thnee to síx) and seven days, nespectively. The number. of days nequined to complete the finst two instans and finst thnee instars combined was estimated. to be 10.3 (nange, nine to 11) and 17.3 (nange, 16 to 18) days, nespectively. 4.1.6.7 Timing of lanval control To obtaÍn maximum effectiveness fnom an insecticide application fon contr:oI of sunflowen beetle lanvae, the Ínsecticide shouLd be applied after: rnost on all of the eggs have hatched, but before lanvae have developed to the late instans. This is based on the assumption that a síngre applícation of insecticide is desir.able, that the 167 insecticide does not affect the eggsr and that most of the darnage by the sunflower" beetle is done by thir.d-, and mone panticulanty, founth- instar lanvae. The last assumption is based on wor:k by Latheef and Hancount ftg72) with larvae of the Colonado potato beetle where leaf consumption by lanvae in instans one to foun vras 2.3, 5.8, 13.8 and 78.2 pencent, ::espectively. This emphasizes the impontance of contnol befone lanvae r"each the founth instan when most of the damage is Iikely to occur. Data f::om the for:¡ fíeld plots wer:e analyzed (Tab1es 27 to 30) to pinpoint the optimal time fon lanval contnol nelative to potential damage to sunfl-owens by the lanvae. The cniteria fon selection of a ta::get date we::e that few eggs be on the plants and that the majonity of the larval population be in the finst and second instans with five peneent or: less in the fou:rth instar". Events in the development of the larvae, such as the finst appealrance of each instan and the DT56 of each instar were then companed with pnoposed tanget dates to find a biological basis fon the selectior¡. In companing potential tanget dates with events in larva1 development, suitable target dates wene found to be nean the date of the DT5g fon the second lanval instar" (L2-DT56). Cha::actenistics of the beetle population in each sampling plot fon this event (i.e. the L2-DT5g) wil-l be discussed in detail. In 1975, at Ste. Jeano the L2-DT5g occunned on JuJ-y 6, aften an accumulation of 534 TUrs (4.+ toLO) (fa¡fe SZ). The nr¡nben of eggs pen plant had peaked at 10.9 on June 17, but most had hatched by July 6 as 168 indicated by counts on July 4 and B which showed 0.7 and 0.9 eggs pen plant, nespectively (ta¡le ZZ). On July 4, thene were 4.2 larvae per plant viith first to for¡rth instans representing 45.5, 38.g, 13.5 and 2.4 pencent of the population, nespeetively, wheneas on July B there wene 6.4 larvae pen plant with the instan nepnesentation being 36.7, 33.1, 23.9 and 6.3 peneent, nespectively (ta¡te ZZ). Thus on July 6, the pnoposed ta::get date fon larval contnor, app::oxímately 75 pencent of the lanvae wene ín the finst and second insta¡.s, 20 pencent in the thínd instan and five pencent in the founth insta::; in addition an avelrage of less than one egg pen plant nemained. An application of insecticide on July 6 would have eliminated the larvae befone illany lrene able to advance to the destructíve fourth instan. Lanvae developing fuom eggs stíII pr"esent on July 6 would not cause significant damage. It is impontant'to note howeven, that the economic thneshold value of 10 larvae pen plant (Anonymous 1979a) was not neached in this fierd, thus, spnayÍng would not have been necommended. Howeven, the field was sprayed on July 23. rt shoul-d be noted that on JuLy 22, thene wene no eggs present, and thene wene only 3.2 la_nvae per plant with.the ínstan repnesentation being 3.8, 13.9, 30.g and s1.6 pencent, nespectively (ta¡te 27). The decnease in numben of la::vae pen plant fnom 6.4 on July 8 to 3.2 on Jury 22 due to the fact that many lar:vae had compreted developnent and entened the soil to pupate. Any benefits from contnol at such a late date would be questionable. Unfontunately, ttinsurancett delayed or contnor such as that noted is common. 169 rn 1976, at Letellie::o the L2-DT56 occunned on Ju1y.7 on at 613 TUrs (Tab1e 32). The numben of eggs pen plant had peaked on June 22 at. 5.5 pen plant, but by July 7 most had hatched as indicated by counts on Ju]-y 6 which showed 0.3 eggs pen pt_ant (fa¡te Ze). On July 6, there wene 2.4 larvae per plant with the fou:r instans repnesenting 26.4,52.g, 17.4 and 3.3 pencent of the sample, respectivery. Thus, on the tanget date of July 7, few eggs nemained and a very small pnoportion of the lanvar population was in the fou::th instan. Howeven, since thene wene less than 10 lanvae Pen plant, contnol would not have been necommended. Neventheless, the coopenaton decíded to spna5r and on July 20 all the field, except the sampling plot was tneated. Again, it shoul_d be noted that on July 20 thene wene no eggs on the plants and that thene wene onry 2.1 lanvae pen plant with the insta:r nepnesentation being 0.0, g.1, 18.3 and 72.6 percent, respectively. considening that at a population level of 2.1 lanvae pen plant, well below the established economic thneshold, contnol woul-d not be economical and funthen that it was cannied out when most of the lanvae wene in the for:¡th insta::, it is doubtful that the gllower neceived any economic netur.ns from contnolling the beetle. rn the 1977 prot at ste. Jean, the L2-DT50 occurned on June 21 or at 554 TUts (fable 3Z). The nurnben of eggs pen plant had peaked at 7.3 on May 25, but most had hatched by June 21 as indicated by counts of 0.2 eggs pen plant (faUte Zg). On June 21, thene wene 7.2 lanvae pen prant with the fÍnst to founth instans nepnesenting 26.3, 41.g, 29.6 and 2.5 pencent of the sample, nespectively. Thus on the pnoposed 170 tar"get date of June 21 , few eggs wene pnesent and the 1a::vâ:1 population was nelatively young. Howeven, the lanval count did not exceed the economic th::eshold value, and contr"ol was not necommend.ed non cannied out. rn the 1977 plot at Lowe Fanm, the L2-DT50 occumed on June 30 or at 650 TUts (Tabte 32). The nunber of eggs pen plant had peaked at 7.7 on 'June 17, but most had hatched by June 30, as indicated by counts of 1.1 eggs pen plant on July 1 (Table 30). on.Iuly 1, thene wqre 10.g larvae pen plant with the insta:: o"po."urrtation being s6.g, 33.4, 2g.5 and 1.3 pencent' nespectively. An application of insecticide on June 30 wouLd have eliminated the lanvae befone many reached the fou::th instan and the few lanvae that would have developed fnom the nemaining eggs would not cause significant darnage. Since the lanvaI density exceed.ed 10 pen plant, control woul-d have been in onde:: but was not cannied. out due to othen considenatíons. Howeve::, simulated rrcontrolsrt on vanious tanget d.ates wene cond.ucted in this field; r.esults will be pnesented in Section 4 . 1.6 .7 .t. Ïn summanyr the L2-DT59 is pr:oposed as a tanget date for contnol of la:rvae. rn the foun sampling plots studied, the L2-DT5g occu:rred, on avenage, on Ju]-y 1 on at 5gg TUts (Table 32). The population on the pnoposed tanget date was composed of about 75 pencent finst-, and second-instan lanvae, 20 pe::cent third-instan lanvae and five pencent fourth-instan Iar.vae. The numben of eggs pnesent on the tanget date was less than 15 pencent of the peak nunber of eggs reconded. Methods of pnedicting when the L2-DT50r or the tanget date occnrs wil-l be presented in Section 4.1 .6.7.2. t7t 4.1.6.7 .t Testing vanious tanget dates at Lowe Fa::m, tg77 rnsecticide tnials r^rene not conducted to test the pr.oposed target date in the field at Lowe Fanm, but the effect of marrual- nemoval of lanvae, simulating chemical contnor at va::ious times duning the l-anval peniod, was detenmined (ta¡te 34, Figune 20). Samplíng fon eggs, adults and lanvae of the sunflowen beetle was cannied out twice pen week at Lowe Far.m (Sections 3.4. t 3.4.4). counts wene nade on plants in plots nandomized according to sampring dates. Eggs and adults wene not distunbed, but arl larvae obsenved durÍng sarnpling vlere removed fnom the plants and pnesenved in 70 percent alcohol fon subsequent determination of instans. prants which had oniginally been sampled on June 21, 24, 28 and July 1, 5 and B fon the larval development study were resampred on Jury 13. The effect of lanval ::emoval at these diffenent times was assessed. A visual r"ating of defoliation was also cannied out on July 13. An indication of suitable target dates fon lar.val contnol was thus obtaíned.. ' June 21 was not suitabl-e as a ta.rget date fo:: lanval- contnol because a lange pnopontion of the sunflower: beetle population was in the egg stage and was not affected by lanval ¡emoval. On June 21, an average of four rar"vae per plant vrere collected and 3.7 eggs pen plant were left undistu:rbed (Table 30, Figu::e 20). OnJuly 13 an additional 5.1 lanvae pen plant wene collected (table 340 Fígure 20). Larvae collected duning resampling on July 13 would have oniginated fuom eggs that were Pnesent on June 2t or fr.om eggs that wene laid aften June 21. Some of the lanvae present on July 13 may have oniginated from adjacent Tab1e 34. Numbe:: of la::vae of the sur¡flower beetle, Zygogramrna exclamationis, necovened on July 18, !g77 fnom plants at Lowe Fanm, Manitoba, following m"n.il"emffiFF\rae on va::ious dates fnom June 2t to July 8, L977 s 1 since Tneatment Fírst Days s].nce plants Number of lanvae Iant on J date Apr:il t hatch finst tch s t02 L4 1.6 Ju:e 24 590 187 t7 98 0 .18 0 .88 1. B0 1.08 3.94abc Jur¡e 28 638 18s 2t 68 0 .29 1 .09 0.68 0. 51 2.57 be JuJ-y t 659 206 24 B9 0. 33 0 .89 0.53 0. 36 2.tt bc Ju.l-y 5 7t0 257 28 88 0.tt 0.47 0 .33 0.41 1.32 c July I 747 294 31 101 0. 04 0.24 0 .14 0 .40 0.82 c ( ,Ju1y 13 check ) 802 349 óÞ 220 0.21 0 .85 1.79 3. 09 5.94a lThennnl r¡níts (TUts) catculated using 8.4oc as the lowen thr.eshold temper.ature, and using daíly ai:r data from the Monnis Ïleathen Station. zLt, Lz¡ L3 and L¿+ = finst, second, thind and fourth instan la::vae, respectively. 3Means followed by the same letter ane not significantly different at the Seo lelel acconding to the Student- Newman-Keul test \¡F l\) t73 Figure 20. Eggs and lanvae of the sunflower beetle, Zygognamma exclamationis, colrected dur"ing finst sampling and later" nesampling of plots at Lowe Fanm, Manitoba ) 1977. E = eggs) tr 2, 3 and 4 = finst- to fourth-instan larvae. Original Sampling Resampling P¿y Day ( Juty 13 ) J u n e ffi 21 w J u n e 24 ffit J u n 9 -r¡r+> 2A tr J u I v -Ð> I fll J u I v -r€> 5 fl'l J u I v 13 tu 404 o Number/Plan t Number/Plant 174 plants fi:om whích Ia::vae had not been nemoved, but the numb.en woul_d be insignificant because of the sed.entany behavÍou:r of the lar-vae. Thene was some foliage darnage on July 13 on plants f::om which lanvae had been nemoved on June 21, especially on the uppenmost leaves (figure 2Ia), but thene was rþre danrage on plants which had no lanvae ::emoved, (Figune 2td). Thus, arthough the effect of larval nemovar on June 21 was evÍdent, a laterl target date would have been advantageous. Removal of lanvae on June 24 was also not suitable as a target date because eggs wene still pnevalent. on June 24, an average of seven lanvae pen plant wene coll-ected and 2.7 eggs per: plant were left undistunbed (Table 30, Figune 20). On nesampling on July 10 an additional 3.9 lar:vae wene collected (fabte 34, Figu:re 2O). A somewhat laten tanget date would have been npne effective. June 28 ütas a rnone suitable tanget date fon Ia::val contnol . On that date, thene wer:e 13.4 lanvae and 2.2 eggs pen plant (Table 30, Figune 20), while on July 13, the::e were an additional 2.6 lanvae pen plant (table 34, Figure 20). 0n June 28 the lanvae were all in instans one to three; none had neached the fou::th instar. plants fnom whích l-arvae had been nemoved on June 29, exhibited little danage by July 13 (Figure 21b) and the few lanvae that nemained had not caused significant damage. July 1 was also a suitabre tanget date fon ranval control because the najonity of the eggs had hatched and the Ia:rvae ,nrere sti1l reratively young. on July 1, 10.8 ranvae pe:: plant wene collected and one egg pen plant was left undisturbed (Table 30, Fígune 20); only an 1.75 Figure 21. Leaf damage on sunflowens, Heliånthus annuus, at Lowe Farm, Manitoba on July rg. rg77 following manual_ nemoval of farvae of the sunflower" beetl-e, Zygqglamrna ..--exclamationis, on: (A) June 21, 7977 (B) June 28, Ig77 (c) July 5, rg77 (D) July 13'- tg77 176 additÍonal 2.! la::vae per plant r¡jene pnesent on July 13 (Table 3+, Figune 20). July 5 was not considened suitable as a tanget date because by that time the 1àr"va1 population was rnatuníng napidly; of the 10.S l-anvae pen plant collected, 1.6 on about 15 pencent wene in the founth instar. Near'ly all the eggs had hatched by this time and on-ly an additiorral 1.3 Iarvae pen pJ-ant wene collected on July 13. Thus although few lanvae were Pnesent aften July 5, considenable damage fuom.ear"Iien feeding was evident as indicated by a companison wíth untneated. plants and plants tneated on June 28 (Figures 21d and 21c). Jury B was not suitabre as a tanget date eithen because the lanvar popuÌation was alneady well advanced in age. on JuJ_y g, of the 7.8 lanvae pen prant collectedr 2.r or. about 27 pencent were in the founth insta:: (fa¡le SO). Some larvae, ín facto would have completed deveropment by July 8, and left the plant to pupate in the soiJ_. on July 13' an average of less than one ranva pen prant was pr.esent. Tf controls had been left until JuJ-y 13, the l_anval populatÍon would have been mainly Ín the late instans (Tabte 34, Figur"e 20). Of the 5.9 lanvae pen plant collected on Jury 13, 3.1 on about s3 pereent wene a.Lready in the for:::th instar. The population had decl_ined because many la::vae had dnopped to the g::ound to pupate. Extensive defoli-ation $ras noted on plants which had no lar"vae removed pnevious to JuIy 13 (rigune 27d). considening the nesults on l-anval- d.evelopment (Tables 30, 34 and Figune 20) and damage (rig:u:nes 2!a to 21d), the best tneatment d.ates 177 were June 28 and July 1. At this time, lanvae wene stil-I mainly in the finst three instans, most of the eggs had hatched, few founth-instan lanvae wene Present, and nelatively few lanvae developed aften these tneatment dates. June 21 and 24 wene not suitab]e because too lange a propontion of the population was in the egg stage and, as noted pneviousry, would not be affected. July s and B wene also not suitabl-e because the lanval- populatíon was too fan advanced with most lanvae in the thind and founth instans; mueh damage had a¡"eady been done. Fnom these nesul-ts, thene would appear to be a penÍod of appr:oximately one week duning which spnaying would be r.ecommend.ed fon optimal contnol. rt ís ímpontant to note that the tanget date suggested on the basis of the L2-DT50 was June g0 (Table 32) which coincídes with the best tneatment dates estabrished above. This supponts the use of the L2-DT5o as a tanget date fon applications of insecticides fon contnol of the l_anvae. 4.7,6.7.2 PnedÍction of date of L2-DT59 Assumíng that the L2-DT56 is a suitable tanget date fon larval contnol' a practical method of pnedíctíng the date is desinable. Foun methods ane proposed, all of which ane based. on data collected over a pe:riod of thnee year.s fr"om the fou:r sampling p1ots. The finst method is simply to use the mean calendar date of the L2-DT50. Fon the foun samplÍng protso the obse::ved date fon the L2-DT50 nanged fnom Jr:ne 27 to July z with a mean of July 1 (Table B2). .Tuly 1 couLd thus be used as the tanget date fon la:rval contnol. The method L78 has the advantage of being veny simple but the disadvantage. of not compensatíng fon year to yean or fÍel-d to field vaniations. The second method pnoposed is to use the mean numben of TUrs accumulated (8.4oc rolo) fuom Apnil 1 to the date of the L2-DT59. This nanged fuom 534 to 650 with a mean of 5BB (Tabl_e 32). Fon this method, the ta:r'get date fon lanval- contnol would be the date coinciding with the accumulatÍon of 588 TUts fnom Apnil 1. changes in tempenature conditions fnom yean to year at?e taken into account wíth this method, but field to field differences ane not. The thind method pnoposed is to use the mean numben of days fnom the date of finst hatch to the date of the L2-DT56. For the four sanpling plots, the obsenved number: of days fnom first hatch to the L2-DT59 nanged fnom 19 to 23 with a mean of 21.3 days (ta¡fe OS). The tanget date for lanval contnol would thus be 21 days fnom the date of first hatch in the commer"cial sunflower" fiel-d beíng considened.. This method has the advantage of alrowing fon fíeld to field vaniation by pnovidíng a stantíng point fon the pnediction which is linked to the life histony of the beetle. The method, howeven, d.oes not compensate fon vaniations in tempenatr¡:re duning the pnoposed 21 day peniod. The founth method pþoposed is to use the mean numben of TUrs (8.4oc rolo) fnom the date of finst hatch to the L2-DT59. Fon the four sampling plots, the obsenved number" of TUrs fo:: this peniod. nanged fuom 152 to 248 with a mean of 204 (Tab]e 35). Thus, the fou:rth pnoposal is to use 204 TUts fnom finst hatch as a predicton of the tanget date for. contnol of the lanvae. ThÍs method has the same ad.vantages as Method 3 779 Table 35. Accumulated the::mal units (tU's)1 and days from the date of finst hatch to the DT5Ot fo:: second-ínstán lanvae of the sunflowen beetle, Zygognamma exclamationis, at fou:: sampling p1o ts ín south -cenFal-ffiEoÐrcZS-- tg'ZZ Ste. Jean, 1975 248 19 Letellíen, 7976 2t9 22 Ste. Jean, 7977 lJZ 2t Lowe Fanm, !977 t97 23 Mean 204 21.3 lThenmal units (TUts) calcu]ated using B.4oC as the lowen thneshold tempenatu:re, and using daily ain tempenatu::e data fnom the weathen statíon at l,lonnís, Manitoba. 'lT5O = development time fo:: 50% of cohont. 180 excePt that Method 4 can compensate fon temperature vaniatíons dunÍng the peniod aften finst hatch. The foun methods pnoposed wene tested as pr"edicto::s of the date of L2-DT59 ín each of the fou:: sampling plots. llíth July 1 (Method 1) as the predicted date, thene was an erllor of one to 10 days oven the fou:r plotso while with the use of the mean accumul-ated TUts fnom Apnil 1 (¡lethod 2) the enron nanged fnom two to six days (Table 36). Using 21 days aften fi::st hatch (Method 3) as a pnedicted date of the L2-DT56, the er':ror nanged fnom zeno to two days oven the four plots, wher:eas using the mean accumul-ated TUrs from finst hatch (Method 4) to pnedict the date, the enron r:anged f::om one to five days. Thus, Method 3 was the rnost accunate and pr:obably is the nost pnactical and sinple method at pnesent sínce it does not nequir"e the calculation of a TU accumulation. Howeven, it does nequi::e that g:rowers check their fields veny canefully at least twice pen week to detenmine the date of fir"st hatch. G¡'owens shoul-d also make counts to d.etenmine whethen contnors are necessany at all. cu:::rent necommendations indicate that lanval cont:'ol- should be undentaken at population Levels of 10 o'morle lanvae per" prant (Anonynrous 1g7ga, 1g7gb). The validity of the fou:: methods pnoposed stitl nequínes pnactical testing using insectícid.es since all recommendations ar:e based solely on biological obsenvations. The valid,ity of the pnedictons duníng sevelle outb::eaks of the sunflowen beetle also should be examíned. The necommendations pnesented hene shoul-d pr:ovide an accunate basis fon timing of insecticide tníals. 181 Tabl-e 36. Fnedicted date and ernor in pnedíction fon the DT56 1 of the second lanva1 insta:r of the sunflower beetle, Zygognamma-åxclamationis. at foun sampling plots in south-centnat ¡lan-ÏtõEãllõ-2il1r-fr, usfi'f;; methodse Obser"ved samptine plot date Dffilã EEEîõî 5ã5_*ffi ¡ffiæ," Ste. Jean , !g75 July 6 July 1- Letellien, 1976 July 7 Juty 1 6 July s 2 J"li 6 i_ .Iuty 6 1 ste. Jean, 1977 June 21 July ,Ju¡re 1 10 24 3 June 21 0 June 26 S rune 30 rury ::l:_:::i,__:::r__ 1 1 rune 24 6 ru¡re.2e 2 ruly r t Tota1 22 t7 10 tlT50 = development time for 50% 2Method of the cohont. 1 - Avenage caJ_endan date (Uufy 1) to the Lc_DTqn. Method 2 - Average number of thenmal units (sBB) rráirrg-ö.4oc as the lowen thneshold tempenatu:re fnom Apníl 1.of.the :respective yean to the L2-DT!6. Method 3 - Avenage numben of days (Zt) fnom tire date of fir.st tatcñíng"io the L2-DT5g. Method 4 - Avenage number" of thenmal units (ZO+) using g.4oc as the lower. thneshord tempenatune fnom the date of finst hatching to the L2-DT5o. t82 4.1.7 Pr"epupal and pupal stages 4 .L.7 .! Desc::iption The matr¡¡e for::rth-instan la:rva entens the soil near the base of the plant and fonms an eanthen cell at a depth of two to 10 cm. Wíthin this cell the lanva becomes almost globuJ.an and without nol-ting entens the pnepupal stage; a1l the mor:phological features of the lanva ane retained (figu::e 1d, p.2) The pupa nesembles the adult in size and shape. rt ís exanate and pale yellow at fÍrst with a gnadual dankening of the eyes, mandibles and tansi as it matunes (Figune 1e). 4.7.7.2 Pnepupal and pupar development dunÍng labonatony neaníng 4.7.7.2.1 Rate of develgpment at varíous constant tempenatunes The dunatíon of the pnepupal and pupal stages of the sunflower. beetle was detenmined at each of 15 t tog, 20 t 1oC, an¿ 25 ! IoC. Pnepupae wene obtained from la::vae neaned in the constant tempenatune tnial descnÍbed ín section 4.1.6.4.1. Matu::e for¡rth-instan ranvae wene plaeed in nound plastic containens (7 cm high, 10 cm wid.e, and covened with scneen) which contaÍned. about 3 cm of ¡noist sand. The initial number of lanvae at each tempenature was 32, 34 and 3s, nespectively. The pnepupal stage was assumed to have begun when the beetle entened the sand to fonm a pupation chamber". At 15oc, pnepupae were sifted fnom the sand five days afte:: the lanvae had entened. the sand while at 20 and 25o the pnepupae hrene sifted out of the sand thnee days aften lar"var entr"y. Following r:emovar fr"om the sand., the pnepupae 183 welle placed in container:s sÍmilan to those used fon the matpr"e larvae, except that moist venmiculite was used ín place of moist sand (Fígune 14b, p.13î). Daí1y obsenvations lrene nade to necord morts to the pupal and adult stages. Following the pupal molto exeised sunflowen l-eaves were placed in the moist vermículite to determine when feedÍng by the tenenal adult began. The dunation of the pnepupal and pupal stages was affected by temperatune. At 15, 20 and 2soc, the pnepupal peniod lasted an avenage of 10-8, 6.7 and 4.7 days, nespectively, and the pupal peniod lasted 16.4, 10.1 and 7.2 days, nespectively (fa¡te aZ). The conbined pr.epupal pupal and pe::iods at the thnee tempenatur"es $ras t:nus 27.2, 16.9 and 11.9 days, r.espectively. Rogens (tgZZ) repo::ted that at 27 ! 2oC, the pnepupal and pupal stages of the sunflowen beetl_e lasted 4.8 and 6.7 days, respectively. This is similan to the values obtained at 2SoC. 0n completion of the pupar stage, the s'nflower" beetle goes thr"ough its final molt and changes to an adult. The tenenal adul-t nemains inactive and does not feed fon one to four days forlowing ecdysis. This pnefeeding peniod of the tenera] adul-t lasted an average of 2.7r 2.0 and 1.3 days, nespectÍvely, at tempenatures of 15, 20 and 25oc. rn the field, this pnefeeding peniod pnobably takes place in the soíl within the pupation chamben. The total subtennanean peniod, that is, the pnepupal and pupar peníods, and the pnefeeding adurt stage combined, was 29.9, 18.9 and 13.2 days at 15, 20 and 25oc, nespectívery. At 15oc, two of 32 pnepupae died while at 20 and 25oc, one of 34 and one of 35 died, nespectively. Based on the initiar numben of 184 Tab]e 37. Developmental- time (days) of prepupae and pupae, and times fon vanious combinations of immatu::e stages of the sunflowen beetle, Zygognamma exclamationis, at three temperatures. Tempenatu::e Dunat mmature sta (t roc) PP-P Lr-P 15 Mean 10 .8 16.4 27.2 63.8 66 .6 S.E; 0.2 0.2 0.4 0.5 0.5 Range 9- 13 14-18 24-30 60-71 62-74 N 30 30 30 30 29 20 Mean 6.7 10.2 16 .9 36 .6 3B .6 S.E. 0.1 0.1 0.2 0.3 0.3 Range 6-B 9-1 1 15-19 34-40 36-43 N J.l \) .) 33 JJ 25 Mean 4.7 7.2 11 .9 zt.,) 28.6 S .8. 0.1 0.1 0.1 0.3 0.3 Range 4-5 6-B 11-1 3 25-33 27 -3s N 34 34 34 34 34 1PP = prepupal P = pupa; Lr = fínst-instan lanvar A = teneral adult stanted feeding. 2lnfonn¡ation on lar"vae fnom Tabl_e 20. 1Bs finst-instan la¡vae at each temperature, the pencent montality in the pnepupal stage was 4.8, 2.5 and 2.5 for the 15, 20 and 25o treatments, nespectively (Tabte 38). No montality was noted among pupae at any of the thnee tempenatures tested. 4.1.7.2.2 Estimated ToLO and TU nequinements Results fnom the constant tempenatune tnial (Sectíon 4.1.7.2.!, Ta-ble 37) were used to estimate the l-owen thneshold tempenatune (folO) and the Theoneticar thennral unit (Theon. TUrs) nequinements fpn the pnepupal ar¡d pupal stages of the sunflowen beetle. With a knowledge of the ToLO and the TU requinements fon each stage, the nate of development can be pnedicted fon any tempenatune negime. An estimate of the ToLo was carcurated using the X-intercept method of Annold (1959) (Sections 2.S.1.1 and 4.1.5.3), and an estimate of the TU nequinements was calculated using equations fon regnession on rate of development (Section 4.1.5.3). The estinrated ToLO fon the pnepupar and pupal peniods was 7.3 and 7.4oC, nespectively (Tabfe SS). The estir¡ated ToLO fon the pnepupal and pupat peniods combined was 7.4oc cornpaned. to 9.9o fo:: the egg stage (Section 4.1.5.3) and 7.3oC fon the complete 1anval stage (Section 4.1.6.4.2). The linea]ô negnession line (Curve B) for the rate of development fon the p::epupar and pupal stages, as shown in Tabre 39, is depicted in Figu:re 22. The x-intencept of curve B indicates the ToLo fon the nespective stages. curve A of Figune 22 was calculated using the regnession equations fron Tab1e 39 and solving for" y (days requined 186 Table 38. Pencent montalityl fon prepupae, pupae, and combinatÍons of immatune stages of the sunflower: beetle, Zygog::amma exclamationis, at thnee temperatunes. empenature Nurnben o Pencent montality of_immature stages ( t 10C) l-ar:vae L r -L,. 15 42 23 .8 4.8 28.6 20 40 15 .0 2.5 t7 .s 25 40 12.5 2.5 15 .0 19o montal-ity based on 2PP=prepupa;p= initial number of Ianvae. pupa; Lr-L,* = finst- to founth-instan lanvae. 787 Tab]e 39. Regnession equatÍons, coefficients of determination, estimated thr"eshol-d tempenatures (ToLO), and theoneiical_ ther"mar unit (Theor. TUrs) nequinements fon development of pnepupae, pupae and combinations of immatu::e stages of the sunfl-owen beetle, Zygognamma exclanntionis. Coefficíent of 3 Regnession equation2 r determination TOLO Theor". q Stage 1 (y=a+bX) (rz) (oc ) TUrs PP Y -0.08664 + 0 .01186X 0 .999 t.ó 84 P Y -0:0s834 + 0.00790x 0 .999 7.4 127 PP_P Y -0.03502 + 0.00475X 0. 999 7.4 27t L r-P Y -0 .01545 + 0.00210x 0.996 7.4 476 Lr -A Y -0.01469 + 0 .00200x 0.998 '1 L! 500 PP pr.epupae; = P = = finst-instatî larvat = teneral adu-l_t star.ted feeding. 2411 values nounded five places 3Y to = neciþnocal of number oC. aval-ues of days, X = temperatune in are fnom the negression equation r"åunded to the nearest unit. 188 Figr:¿"e 22. Days nequined to comprete development and r:ate of development of plrepupae and pupae of the sunfrowen beetle, Zygognarnma exclamationis, at constant tempenatunes PUPA 12 T'= 7.3'G T'= 7.4'C lo T.U.'s = 84 T.U.'s -- 127 8ø (E ô o 20 24 2A 189 fon devetopment) fon each value of X (neaning tempenatune).. Cur"ve A thus is an estímate of the mean developmentar time, in days, fon the prnepupal 0n pupal stages at vanious constant tempenatures. The estimated Theo:r. TU nequínements fon the p::epupal and pupat stages wer:e 84 and 727, respectively, using ToLO rs of 7 .3 and 7 .4oc gg). (ta¡re The Theon. TU nequinement fon the pnepupal and pupal stages conbined was 211 using a ToLO of 7.4oC. 4.1.8 Development in the laboratony fnom hatching to adult emergence 4.1.8.1 Rate of deveropment at var"ious constant tempenatt¡nes An estímate of the peniod fnom hatching to adul-t emengence þras made usÍng data fnom lanr¡al, pnepupal and pupal development studies (Tables 20 and 37). The numben of days nequined to complete development fnom the beginning of the fÍr-st instan to adutt was 63.8, 36.6 and 27.3 at 15, 20 and 25oC, nespectÍvely (fa¡le 37). Rogens (tg77) nepo::ted. that the same developmental pe::iod nequined 26.6 days at 27 ! zoc. An avenage of 66.6, 38.6 and 28.6 days at 15, 20 and 2soc, nespectivery, was nequined to comprete development from the beginning of the finst instan to the day the tenenal adu-t-t stanted feedÍng (ta¡re gz). The influence of temper:ature on the nate of devel-opment of the sunflower beetle is thus evident. Fo¡ example, the developmental peniod at 15oc is mone than double the developmentar peniod at 2soc. Thus, pnevailÍng temperatures must be considered when estímating the numbe:: of days nequined to complete a gÍven stage in the field. Based on the initial numben of finst-insta:: lanvae, the pe::eent montality in the labor.atony tr.ial fon al-l stages combined was 2g .6, 17 .s 190 and 15.0 fon the 15r 20 and 25o tneatments, respectively (ra¡te gg). Rogens (1978) and Thompson noted 35 pencent montality duning the same developrnental peniod when the beetle vlas ::eaned in the labonatony at 26 t 2oc on the sunflowen Hybnid g96. rn a later. study Rogens and Thompson (rsgo) noted 24 pencent mortality when the beetle gras reaned. on the same cultivan at 27 ! 2oC. 4.1.8.2 Estimated ToLO and TU requínements An estimate of the ToLO and Theon. TU r"equinements for development of the sunfl-ower beetle from the fí::st instan to the adult stage was estimated usíng the data fon the nate of development pnesented in Tabres 20 and 07. A ToLO of 7.4o was d.etenmined fon the developmentar per"iod fnom the finst Ínstar" to completion of the pupar stage (ra¡te sg). The same ToLO was detenmined fon the per:iod fnom the first instan to first feeding by the tenenal adul-t. The Theor. w nequinements for" the two above noted pe:.iods wene 476 an respeetÍvely (TabLe 39). The l-inear regression line (Cur"ve B) fon the nate of development fon the peniod, finst instan to feeding by the tenenal adult, is shown ín Fígune 23. The X-intencept of cunve B indícates the ToLo. cur"ve A of Figure 23 is an estinate of the rnean developmental tÍme, in days, fon the complete peníod at vaníous '.t+. constant tempenátunes . 4.1.9 The p::ehibennation adult The sunfr-owen beetle has only o*e genenation pen yean in Manitoba (Section 4.1.9.2), and it over"wíntens as an adult (Section L9T Figune 23. Days nequined to complete d.evelopment and rate of development fon the peníod fz'om enengence of first-instan lanvae to the start of feeding by adults of the sunflower beetle, Zygog::amma exclarnationis, at constant tempe::atures FIRST INSTAR TO ADULT \ \ \ T'= 7.4'C \ T.U.'s = 5OO \ T \ U' o \ ô U, \ o o B ao 26 28 L92 4.1.1.1). The new-genenatíon adurt which emerges fnom the pupal- chamben wíIr thus be nefenred to as the prehibennatíon adult. 4.1.9.1 Descniption, feeding, and behaviou:: Pnehibennation adur-ts ane identicar in appearance to posthibennation adults except that the elytra of the pnehÍ-bernation adults tend to be shinier and soften than the elytra of posthibennation adults. These visual diffenences along with behaviounal diffe¡ences were used to distínguish the two genenatíons of adu-l_ts. BehavÍor¡r: of pnehibennatíon adults diffened fnom posthibennation adults. PnehibennatÍon adults appeaned inactive and usually duning the day wene noted nesting amongst the bnacts of the developed flowen head on on the undensides of the uppeï'rnost leaves of the prant Pnehíbernation adults were not noted to fly or othenwise dispense. Mating and egg-Ìayíng by pr"ehibennation adults hras not noted. in the fÍe1d. Díssections of pr:ehibennation adul-ts neveal-ed. that females had immatu::e ovaries (stage r previtellogenesis) and that mating had not taken place sínce thene were no spermatazoa in the sperrnathecae (Section 4.1.1.2) (tabte 7, p.B1). Pnehibennation adults fed on the last fonmed leaves on the matuning sunfl-ower" plant. Ïlhen pnehibennation adults wene abundant, damage to the uppelr leaves was noticeable (figr:r,e 2d, p.4). Companed to the amount of damage caused the folrowing spr"ing by these adurts, as posthibennation adults, and the subsequent danage by thein lanr¡al pnogeny' defoliation by pnehibernation adul-ts appeaned insignificant. 193 4.1.9.2 FÍnst obsenvatíon of pnehiSennatíon adults and dunation of the pr:ehibennation peniod fnfo:rmation on the dates of occunr ence of pnehibernation adul_ts ín the field was obtained fnom the samplÍng plots at Letel-Lie::, in 1976, and at ste. Jean and Lowe Farm, in !g77. At Letellien, in 1g76, pnehibennation adults we::e first obsenved on Juty 30 and last obse¡ved on Septemben 14, a peníod of 46 days (Table 28, p.154). fn 1r977o at ste. Jean, pnehibernation adul-ts wer"e noted fnom July 1g to 26, a penio¿ of only seven (table days 29, p.156). Tn the late seeded plot at Lowe Fanm, pr"ehibernation adults wene finst noted on July 29 and last noted August 23, a peniod of 25 days (Table 80, p.159). The dur"ation of the pnehibennation peniod was estimated in the labonator"y by obsenving adutts which had been neaned fnom the constant tempenatu::e (Section tnial 4.1.6.4 and 4.1.7.2). Adults neaned at 15oC nemained above gnourrd an avenage of 13.4 (range, nine to 23) days pnion to entening the soil to hibernate. 4.1.9.3 Estimated numben of days and rurs nequined to complete development fnom hatching to emergence of pnehibennatíon adults An estimate of the numben of days and TUrs nequined to comprete development frorn hatching to emengence of pr-ehibennation adults was obtained fr"om fierd data fnom the 1976 sampling prot at Letelrien and the 1977 prots at ste. Jean and Lowe Fanm. rn these thnee tests, prehÍbennation adul-ts wene finst noted between Jury 19 and 30 (mean, July 26), a period of 45 to 52 d.ays (mean, 49 days) or. aften an 194 accumulation of 533 to 592 (mean, 555) thenmal units (Z.4oC ToLO) following finst hatch in the nespective fields (ta¡te +O). Forty_nine days and 562 TUts are, thenefone, estimates of the tíme and ru nequirements for" deveJ-opment thnough the rarval, pnepupal, pupal and tenenal adult stages in the field. In compar.ison, 500 TUrs (7.4oC ToLO) was the estimated nequinement fon the same combined. life stages ¿nden contnolled envinonment conditions in the labonator.y (Table 39 and. Figure 23). 4.1.9.4 Number of generations pen year All data gathened du::íng this study supponted the observations of Criddle (tgZZ) and Westdal (fgZS) that the sunflowen beetle has one genenation perl year ín Manitoba. rn the 1g76 and 1g77 sampling ptots, eggs l^rene pnesent while posthíbennation adults $reÌâe present, but not while pnehiber:nation adults wene present (Tables 28 to 30, pp.154,1s6, 159). All pnehibe::nation females examined wene found to be sexually ímmatune (Section 4.L.1.2), thus supponting the obsenvation of only one genenation pen yean. rn Manitoba, new-gene:ration adults feed fon app::oxirnately one to thnee weeks afte¡. whích they enter. the soir to hibernate without mating on laying eggs. wal-ken (rsso) noted two generations pen year in Kansas and Rogen s (1977) speculated that the sunflowen beetl-e coul-d have thnee generations per yea:: Ín Texas, but he had no field data to support his theony. 4.1.9.5 Facto¡.s affecting diapause induction Five combinations of photopeniod and temperature wene tested in the l-abonatory with the objective of obtainÍng a non-diapausíng cultune 195 Tabr-e 40. calendar date and accumulated thenmal unitsl (TU's) at finst obsenvation of ranvae and new-genenation adults of the sunflowen beetle, Zygognamma exclamationís, in thnee sampling plots in south-cenffiãEoF% Tg-ñ:IOfi w-genenat adults La::vae first obsenved fir"st oþe¡yed Ob"g-=lionlg$g sanprineprot æffiî.y" TU,s Letellien r 19T6 Ste. Jean, tg77 May 31 445 July 19 978 49 533 Lowe Fanm, 7977 June 7 503 July 29 1095 52 592 Mean June 7 464 JuJ.y 26 1019 49 555 lThe:rnar units calculated using 7.4oc as the lowen threshold tempenature, stanting on Ap'ir 1 of the cornesponding yean, and using daily ain temperature data fi:om the !'leathen station at Monnis, Ma¡rito¡a. 196 of the sunflower beetle whích would pnod.uce a ne]iable suppl-y of fertíle eggs. Resul-ts fnom these photope::iod-temperatune treatments also gave insight into possibre factons that control_ the sexual activíty and diapause ínductíon of pnehibennation adults in the fieId. The five líght-tempenatune combinations tested. grere: 15L:9D anð. 22oc; 16L:BD and 150C; 16L:BD and 200C; 16L:8D and 250c; and 18L:60 and 22ac. Adults used for" the tníal wene raised thr"oughout thein life cycle ulder the nespective photopeniod-tempenatune negimes. The larvae had been neaned uricaged on seedling sunflowens and. the pnepupae and pupae had developed in a moistened media such as silica sand, venmiculj.te or soil (Sections 4.1.6.4 and 4.1.7.2). Upon emengence, beetles were pair"ed (1g + td) and examined daily fo:: at least three weeks fon evídence of diapause induction on sexual aCtívity. Critenia for. a non-d.iapausíng individual wene that it ::emained above gnound following adult ec.l-osion an¿ became sexually active, that is, maJ-es a¡ld fenares wou]d mate and femal-es woul-d lay eggs. Diapausing individual-s were adults that fed fon a shont time, did not become sexually active, and subsequently entened the soil to hibernate. A completely non-diapausing population developed only und.er the photoper.iod-tempenatune r"egime of 15L:9D and 22oC (Table 41). Although this tnial was not extensíve, the tnend appeared to be that as day length incneased, the pencentage of individuals entering diapause increased. Tempenature also appeaned. to affect diapause induction since mone than half of the beetres neaned at 16L:BD and 25oc became sexuarly active while al-l beetles nea::ed at the same photope::iod, but 1,97 Tabl-e 41' Pencent d'iapause of male and fema.l-e adults of the sunflowen beetle, Zygogngmpa exclamationis, neaned fonm ranval emergence to adult at diffener:t combinations of photopeniod and tempenatÌr1e Numben o Tempenature beelles obsenvejl % --Photopeniod (t1oçl ffi ffi{iapausel 15L: 9D 22 16 tt 0 0 16L: 8D 1s t7 16L:8D tt 100 100 20 L3 4FS 100 100 16L : BD ôÊ ZJ t7 15 47 .7 40.0 18L :6D 22 _15 16 93.3 100 lDiapause d.etenmined by evidence of hibennatíon diapausÍng behavioun. Non_ individuals sexually active and/on show evidence of ovany rntunation and egg-laying. 198 at lower tempenatunes entened diapause without becoming sexually active. De wilde et al (1959) noted that photoperiod played a rnajon nole in the induction of díapause in the Color"ado potato beetle, whíle tempenature played a minon no1e. They also concluded that the newly-emenged ad.ult is the most sensitive stage, atthough treatment in the lanval stage had some infl-uence. They found, however., that photoper.íod ¿id not have an effect on posthÍ-bennation adults of the Col-onado potato beetle. Roger"s Gsll), in Texas, successfully reaned a non-d.iapausing cultune of the sunfl-owen beetle at 14L:10D and 27oC. 4.1.10 Sunveys fon natunal enemies Sunveys fon pnedatons and panasites of the sunflower beetle wene eonducted f¡nom 1974 to tg77. The majoníty of the obsenvatíons were made duning sampJ-ing of field plots used. to study the bionomics of the sunfl-ower" beetle (SectÍon 3.4). No attempts wene made to quantify the effects of pnedators on the sunflowen beetle population, howeven, the impact of panasítes vlas assessed by deter:miníng incidence of panasitism. 4.1.10.1 Pnedatons of the sunflowen beetle Eight insect species and one avian species we::e obsenved. feeding on one or mone than one life stage of the surrfrowe:: beetle (ra¡te +z). Two species of cocciner-lids of the genus Hippodamia were obser"ved feeding on immatune fonms of the sunfrower beetle. Adults and lanvae of H. convergens Guenin-Menevíl-l-e wene obsenved feeding on eggs and lanvae of the sunflowen beetle. one comprete genenation of Table 42. Pnedatons of various stages of the sr¡nfl-owen beetle, Z5¡gog:ramma exclanationis, in south-central }danitoba, Ig74-I977 COLEOPTERA CARABÏÐAE Lebia atrÍventr:is Say Adul-t Lar va COCCTNELLTDAE Hippodamja convergens Guenin-Menevill_e Lanva, Adu-lt EEg, Larva H. tredecÍmpu¡ctata tibial-is (Say) Adult Egg I'ÍELYRTDAE Collops vittatus Say Adult Egg HEMTPTERA PENTATOMTDAE Penill-iodes biocr:Iatus (Fab. ) Lanva, Adult Larva Podisus n@f:ant::ig (Say) --- - Adul-t Adul-t ,*roo, -- Nabis sp Adu]-t La:rvae NEUROPTERA CHRYSOPIDAE ChrT¡sopa carnea Stephens La:rva Egg, Lanvae AVES ICTERIDAE Agelaius phoeniceus phoeniceus @i;ÎFÐ- L. Adul-t H (O (o 200 H. convengens was reared on the sunflower. beetl-e, in the labo:ratory. Adults of H. tnedecimpunctata tibialis (Say) wene obser.ved feeding on eggs of the sunfl-ower" beetle. Hippodamia specíes wer"e the most common pnedatons noted at Ste. Jean, in 1975 (tabte 43) and at Letellien in 1976 (Table 44) but wene the second most common pnedator.s observed. at Ste. Jean (tabte 45) and Lowe Fanm (fabte a6) in Ig77. Anothen coccinellid, Coccinella tnansvensoguttata nichandsoni Bnown, was noted fnequently in each of the sampling plots, but was not observed. feedíng on the sunflower. beetle in the fierd on the rabonato::y. westdal (rgzs) had noted coccínelIid pr:edatons of the sunflower beetJ_e, but díd not indicate the species involved. The chnysopid, Ch¡ysopa carnea Stephens, hras the most abundant pnedaton at Ste. Jean (ta¡fe 45) and Lowe Fanm (faUte +O) in 1977, the second most abundant at Ste. Jean ín 1975 (table 43) and the thind most abundant at Letel-lien in 1,976 (Tab1e 44). Lanvae of C. ca:rnea wene fnequently observed feeding on lanvae of the sunflowen beetle and pnobably also fed on eggs. The ranvae of c. carnea wene most fnequentì-y obsenved in July when there þrene few sunflowen beetle eggs but when lanvae wene abundant. !{arken (rgao) and vlestdal (rgzs) noted a chnysopid pnedaton of the sunflower beetle, but did not indicate the specÍes Ínvolved. Rogens (fggO) obsenved C. carnea feeding on l-anvae of the sunflowen beetl-e in Texas. The melynÍd beetre, cor-r-ops víttatus say, was a pnedaton commonly encountened in the su:ftowen beetle sampÌing plots. rt fed neadily on sunflowen beetle eggs in the labonatory. c. vittatus was 201 Table 43. Number of pr"edator.s obsenved dr:ning samplÍng fon the sunflower beetle, Zygognamma exclamationis, at a plot at Ste. Jean, ManitobaFZl- Number o tons observe SamplÍng of plants Neu:roptena --HêmTþtffi- Coleoptera date - led u. c.- N-" -- L .a. H. June13 ttg 0 O 0 June17 !22 0 0 0 O O 0 5 June2O t22 0 O 0 June24 t24 0 I O O 0 0 7 June27 66 0 0 Julyt!0200000 0 O 7 Juty4 116 0 o Ju1y8xogoo7o1J.r O 2 5 JuIy11 103 4 O 3 0 1:r Ju1y15 tt2 4 O 1 0 0 Ju1y18 129 7 o 2 o in TotaI 013230 C. c. = Chnysopa calînea lar.vae N. sP. = ñãTFp-.-ã¿urts C.v. = F+õ, pg vittatug adutts L.a. = Lebia atniventnis adults H. sP. = HTÞF-aãiffiFEãurts; rc = tanvae 202 Table 44. Numben of pr"edatons obsenved dr:::ing sampling for the sunfl-owen beetle, Zygognamma exclamelionis, at a pJ-ot at Lete11íer, uanitobalTõ'7õ--- Numben Nurnber o to::s obsenved Sampling of plants U"r¿g!""g HemíÞtena Coleoptena date led c.c. N.so. L.a. H. June4109OOO00 ,Juneg79000O0 June11 72 0 O 1 O O June15 55 0 0 0 tlunelS 0 0 62 O 0 2 O 0 June22 SB 0 0 Jru¡e25 0 O 2ts 62 0 0 4 0 0 .June29 67 0 0 g Ju1y26800303rc 0 0 Ju1y66500100 Ju1y96790300 July 13 63 tt 0 1 0 1:t July16 B0 O 1 July2O O 1 0 56 2 0 0 O 0 JuIy23 74 0 0 0 J,aIy27 O 0 53 O 0 0 0 0 Ju1y30 59 1 O 0 Aug.3440I0O2 0 0 4u9.68910000 Aug.10 56 0 1 1 0 B Aug.13 7g O 2 0 Aug.t7 0 5 58 0 3 0 0 6 Aug.20 52 O 2 0 Aug.24 0 6 67 O 4 0 0 4 Aug.27 54 0 1 Aug.31 O O 4 63 0 0 O 0 3 !ge!:_!__6400004 Tota]. 1B 15 19 48 C.c. = Chnysopa carnea lanvae N.sp. = Nabis sp. adutts C.v. = Coll.ops vÍttatus adul_ts L.a. = Lebia atr.iveñtris adults H.sp. = HÏFÞõ¿ãmlã-Gp. ããurrs; fs = tanvae 203 Table 45. Number of p::edatons obser:ved du:¡íng sampling fon the sunflowen beetle, Zygognanma exclamatiolig, ãt , plot at Ste. Jean, I',tanitobalTsTl-- - r\urrlDer or pl?edatons o.bse::ved Sampling of plants date c.v.ffi H. May25500.0000 May27s0o0oo! May31 0 0 June3i000O7It4100 5 0 z JuneTtOO0OBOT Junelo 7s o June14 o o o B+2* 101 0 O 9 0 t2 45 0 ,June21'June17 0 0 0 0 100 0 0 1 0 t June24 100 1 ,June28 O 2 O 0 100 1 6 O O lrt Ju1y1 1OO 4 0 Julys100160000 0 0 1 .iu1y81O0 1,40000 Ju1y12 100 19 0 0 0 Ju1y15 100 0 5 6 0 0 0 Ju1y19 100 0 0 0 JuLy22 100 g O 1 1 0 L rïu1y26 100 0 0 O 0 O 2 July29 100 0 0 Aug.2tOO0000t 0 0 0 49tu-_!-______1q9______-___s______-_9______9______9______9__ Total 61 O g2 ! 54 C.c. 'l = $IYqq- carnea 3lr-rag N. sp. = Nabis ""sp. aduJ_ts C.v. = Collops vittatus adults L.a. = LèõE:tFiveffifs adul-ts H. sP. = HÏõFãaãñliiliãults; r, = ranvae 204 Table 46. Numben of pnedatons obsenved duning sampling fon the sunflower beetle, zygognanrna exclamationis, ãt p10t at Lowe Fanm, r"ranitobalTEm- - " Sanpling of plants Neunoptera date led C.c. N.s H.s June31000.0104 Jr¡re7t}O0O1O7 June10 101 0 O 0 O 0 Jr:ne14 92 0 0 June17 3 O 0 76 O 0 0 O 0 June21 96 0 O June24 3 O I !72 0 0 1 O 0 June28 77 3 6 Julyt96162O0 2 O 0 Julys89S00O0 Ju1y8104100000 Ju1y12 116 I 1 O rIu1yl5 104 0 0 I O O 0 1 ,-ïu1y19 62 O 1 0 JuIy22 87 0 0 0 g 0 0 0 July26 69 O O 0 O 0 July29 94 0 Aug.28420O0t 0 0 0 ! 4u9.55900000 4ug.91100000s Aug.12 75 0 0 0 O Aug.16 89 I 0 O 0 0 3 Aug.19 79 0 0 åge:-?!------11q_ooooo 0 0 0 Total 30 13 26 C.c. = Chnysopa carnea lanvae N.sp. = ñãÏffiÞ-.ããffiË C.v. = Col-]ops vittatus adults L.a. = Lebia atnívent::is adults H. sP. = EïÞpo-aãïã-EÞ-Eãì¿ts 205 second the most common pned.aton at Lete1lier in 1976 (Table.44) and the most thind common at Ste. Jean in 1975 (Table 43) and tg77 (Tab-le 45) and at Lowe Fanm in Ig77 (talte +O¡. C. vittatus has been reponted as a p::edaton of the fl-ea beetle, Phyllotneta crucifenae Goeze, in Manitoba (cenben 1975) The nabid, Nabis sp. was the four^th most common pned.ato:: observed at Letellien in 1976 (Table 44), but ít was rarely noted dr:ning obse::vations at the othen locatíons in othen yeans (Tabres 43, 45 and 46). Nabis sp. r\ras suspected. of feeding on sr:nflowe:: beetl-e lanvae, but it was not obsenved doing so in the field and. no feeding tnials wene conducted in the labo::atony. Nabis sp. was pnobably a pnedaton of minon impontance consid,ening that most of the individuals at the Letellien plot wene obsenved aften the ranvae of the sunflowen beetle had completed development. The canabid, Lebia atniventnis say, was nane with only foun specimens being obsenved in all- four sampling prots (Tables 43 to 46). Ït was not obsenved feeding on any stage of the sunflowen beetre in the field. (1975) westdal neponted L. atriventnis as a pnedaton of the sunflowen beetle. penilliodes The pentatonid, biocul_atus (faU.), was obsenved feeding on lanvae of the sunflowen beetle. ThÍs obsenvatíon was made in a sunflowen fíeld adjacent to the 1977 prot at ste. Jean. This pnedaton was not obsenved ín any othen field dr::ring the for:¡: yeans of thÍs study. rt has been nepo::ted, as a pnedaton of the sunfl0wen beetle (Anonymous 1923; Rogens 1980), as a pnedaton of the Colonado 206 potato (Bniand beetle 1936; Feytaud 1938; Harcorrt rgTr), a¡rd as a pnedaton of the milkweed l_eaf beetle (tickwart 1977). on one occasion only, the pentatomid., podisus maculiventnis (Say)' was obsenved. feeding on an adult of the sunflowen beetle. ït has also been neported as a pnedaton of the colonad.o potato beetle (Feytaud 1938) Tn 7977 o red-winged btackbinds, Agelaius phoeniceus phoeniceus L., wel:e obsenved feeding on prehíbennation adults of the sunfl_owen beetle ín a sunflowen field adjacent to the ste. Jean sampring pl_ot. Remnants of beetles v¡ene'found on the developed flowen heads. Al-so found llene negungítated pellets pnesunrably from ned.-wínged blackbinds. Dissection of the pellets nevealed numerous fr"agrnents of exoskeletons fnom surrflowen beetles. The impact of blackbinds on the population of pnehiSennatíon adults r^ras not measu:red, but they wene considened. a contnjbuting facton in neducing. the numbers of pnehibennation adults at least at Ste. Jean in 1977 (Table 30, p.159). Howeven, blackbind.s ane a majon pest of sunflowens because they feed on the seed as they matune (Besse:: 1978); the ovenall value of blackbinds would thus be questionable. 4.1.10.2 Panasites of the sunflowen beetle Eggsr lanvae arrd adults of the sunflowe:: beetre wer"e peniodically collected fnom the field wíth the objective of compiJ-ing an inventony of-species panasitÍc on the nespective life stages. Labo::atony pnocedtr::es fon neaning these field collections were as outlined in Sections 0.3 to 3.0.3. 207 Th'ee species of tachiníds ancl a species of ptenomar id. wene near"ed fnom the sunflowe:r beetl-e (Tabl-e 47), and ar"e the finst pa::asites neconded f-::om this host. The tachinid, ì4yiophanus sp., was near.ed fuom adults of the (Figur"e sunflowen beetle 24a). Ihene Ís no pnevious necond. of collection of this parasite. Resul-ts of studíes on the bionomics of Myiophar"us sp. ánd its impact on the sunflowen beetl-e population wíll be neponted in Section 4.2. The ptenomalid, Enixestus winnemana cnawfond., r^ras neared f'om eggs of the sunflowen beetle (Figune 24b). Resu-l_ts fuom studies on the bionomics of this parasític wasp wíIl be pnesented in Section 4.3. The two nemainÍng species of tachinÍd pa:nasites wene of the gênus Dor"yPhonophaga and wene r"eaned fnom lar.vae collected in the field. of 1'349 panasites reaned fi:om sunflowen beetre larvae duning the counse g9.B of this study, 11946 or pencent lrere D. macel_l_a (Figune 24c) whíle only 3 or'0.2 pencent belonged to the betten known D. do'yphor"ge. Resurts of studies on the life hístony of D. macell_a will be pnesented Ín Section 4.4; studies on D. donyphorae !,Ier.e not consid.ered since it appears to be of minon impontance as a panasite of the sr:::flower beetle and has been dealt r^rith by othens (Kell_ehen 1960; 1966). 208 Table 47 . Panasites reaned fnom various stages of the sunflowen beetle, Zygognamma exclamationis, in south-centnal_ I'tanitoba Panasite HYI'ENOPTERA PTEROMALIDAE Er"Íxestus winnemana Cnawfor"d Egg DÏPTERA TACHINIDAE Lanva Lanva Adult 209 Figune 24. Parasites of the sunfrowen beetl-e , zyg;ognamma excl-amationis (a) Myiophanussp.(x8) (B) Enixestus winnêmana Cnawfo::d ( x 1a ) (C) Dorypho:rophaga macêl]_a Reinhand ( x 10 ) 2!0 4.2 Bionomics of Myiophar"us sp.r ê tachinid panasite of adults of the sunfLowen beetle Myiophar"us sp. lras the only panasite near.ed fuom adurts of the sunflowe:: beetle duning this study. The bionomics of this bivoltine panasíte wilr be descnibed bniefly in the following sections. 4.2.1 Ovenwintening MyioPhanus sp. v¡as finst neaned. in Janua:ry, L976 fnom ad.ul_ts of the sunflowen beetre collected on August 23, 1975, as pnehibennation adul-ts fnom a connnencial field of sunfl-owens at Rosenfeld, Manitoba. rmmediately aften collectíon, the beetles wene placed in stonage at goc fon two weeks and then at 2oc untir- needed. on Decemben g, 1g75, the beetles wene nemoved fnom storage and subjected to a 2goc and 16L: BD negime fon five days to b'eak diapause and then wer.e herd at 22ac (section 3.1.1). on Januany 13 and 15, 36 and 38 days, nespectiveryo ínto post-stonage the peniod., an adult of the panasite, Myiophanus sp., eme::ged f,nom each of two sunflower beetres. The panasitized beetl-es wene alive and showed no extennal signs of panasítism at the time they were removed fuom stonage, but wene dead when the par"asites emer"ged. These beetles must have been panasítized pnio:: to corr-ection on August 23. Had the panasitized beetles nemained in the field, the panasites likely would have emenged in the spr.ing. Myiophanus sp. thus oven- wintens in adults of the sunflowen beetle. Daviault (1941) noted that Myiophanus dorsalis ovenwintened. as a maggot in ovenwinte::ing adr:tts of the willow leaf beetle. 2tt To deten¡n-ine the over"wintening stage of Myiophar"us sp., pnehi- bennation adutts and overwintening aduLts of the srnfrower: beetl-e were kilted and dissected. Finst-instar rnaggots of Myiophanus sp. weïe fotmd in the haemocoel in the thonax and abdonren in both col-lections of beetles' No respiratory frnnels r^iere evident non was thene any attach- ment to host tnachea. Finst-instan maggots of the tachinid, Doryphorophaga nncelra, were arso for'd in adur-ts of the stnflowen beetre, but arr- these maggots were dead and encapsur_ated. The two tachinid species were differ"entiated by companing the size and. shape of the nputh-hooks of the fi¡st_instar (rigunes 250 and 29_p.2ag). 4.2.2 Lar"va Deveropment of the larra of Myiopha::us sp., following the oven- wintening phase ' was studied by per.iodically dissecting panasitized. beetres and noting the development of the rnggot. The parasitized beetres wene obtained fncm vanious field collections of p:rehibernation adul-ts which were stoned and subsequentry bnought out of diapause and. neared (Section 9.I.2). 4.2.2.7 Number of instars Myiophanus sp. has three rarval instars. The instar:s were clis- tinguished by a companison of the size and shape of the mouth-hooks. The mean (x sE) tength t of the nouth-hooks was o.t76 t 0.001 mm, 0'327 rnn' and 0'715 + 0.010 mrn fon the three instars, respectively. rhe ueasurenents were based on 10, two and 10 specimens for the three instar"s ' nesPectively. A sketch of the nputh-hooks of the fir.st-instar 272 Figu:re 25. Latenal view of mouth-hooks of finst-ínstan maggot of Myiophanus sp. (S1OX) 2]-3 is pnesented in Figune 25. Dor"yphónophága donyphorae, a comrþn tachinid panasite of the .col-or"ado potato beetle, arso has thnee lanwal instars (Kelleher" 1960). Clausen (1940) stated in his r"eview of pa'asitie insects that tachinids gener:alry have thnee ]anvar instans. 4.2.2.2 Lanra1 behavÍoun and developnent Finst-instar" maggots of Myiopha::us sp. were fou-¡d in the supraoesophageal ganglion of adutts of the srr¡flowen beetl-e that had been out of cotd stor:age and into the diapause-breaking regime fon 10 to 13 days. the maggots were r¡:den the ne:rve sheath along one r-obe of the br"ain and wene about the same size as those noted. in pr.ehÍbernatÍon and overryintening beetles. The¡e was no or:vious feeding on the brain. Usually only one maggot was for¡rd Ín a single beetle, but on one occa- sion two naggots were for'd in a singre beetr-e, one nnggot being in each lobe of the brain. Finst-instan maggots thus appeared to have moved ñnom the thorax or abdornen to the br"ain aften the host was taken fnom col-d stonage. Panasitized beetres failed to nespond to diapause-breaking treatments' rn the l-abonatony, nonparäsitized beetres ernerge¿ from the sand in thein neaníng containens about five days after^ nemoval from col-d stonage and within another five days began to feed., mate and ray Parasitized eggs. beetres, howeven, nemained in the sand and did not feedo rnate on lay eggs. This r-ack of activity by parasitized beetles was presumably caused by the pnesence of the panasite in the brain. Reasons for the entny to the brain were not known, but it may be that 274 the behavioura'l- change by the beetre was advantageous to the parasite. Possibl-e advantages include finstÌy, that the panasite cour-d comprete development Ín the nel-ative sa.fety of the overwinteríng quanter"s of the beetleo and secondly, the delayed erengence by the parasite put it in s5mchnony with the life cycre of the srmfl0wer beetle. strickland (1923) obsenved finst-instan nnggots of the tachinid Gonia sp. ín the bnain of the pare westenn cutwonrno Agnotís onthogonia Monríson, and speculated that the rnaggot gained immunity fncm encapsulation by enten_ ing the bnain. This theony wour-d not appear to appry to Myiophanup sp. sÍnce the naggot enters the bnain after spending months free in the haemocoel dr:ring the pr"ehibernatÍon and ovenwintening phases of the beetl-e' rf the immune theo::y was applicable to l,fyi_qphanus sp., the naþgot woul-d be expected to enten the b¡ain sooner. second-instan maggots were fould in the head of the beetre, but not in the b'ain. sometime r-ate in the finst insta:r o'eanry in the second, the maggot leaves the brain and forms a respinatony firrrnel- with an opening to the exterion thnough the buccal cavity of the host. Du'ing the second instan, the maggot líes with its abdoren in the nespínatory funnel and its mouth-hooks towa::ds the postenion of the host and feeds on the body contents. Beetres containing maggots in the second instan wer"e stirl arive, but were inactive. panasítized beetles containing second- or: thind-ínstan maggots courd be identified by.the pnesence of the respinatony frnnel which appea::ed as a d.ank area inside the head when viewed ventr"a[y thnough a row powe]: dissecting rnicroscope. 215 lfhen the naggot is arnrost furly gmlrn and firr_s most of the body cavity, the host dies. Befone pupation, the naggot makes two openings in the cuticl-e of the host. one is a slit along the postenio_ l-atenal mangin of the abdonren such that the fÍfth abdominal ster"nite is sometimes nemoved. A second slit is made in the inter.segmental menbrane between the pnothonax and the mesothonax such that the beetle is often decapitated. After the openings aïe made, the parasite pupates. 4.2.2.3 Duration of the larval stage The nate of deveropment fon Myiophanus sp. was detennined in the laboratory, in 1976. Srnflowen beetl-es in the pr"ehibennation stage were coll-ected fnom a field of çr:nflowers at Rosenferd, Manitoba on september 5, 1975r.and placed at 9oc fon two weeks forrowed by stor.age at 2oc. on Febnuary 9, 1976, the beetres were taken out of storage and after a conditioning peniod of one week at 9oc were pÌaced in sealed glass dishes containing nroist sand and excised sr.nflowen leaves o and held at 22 t 7oc and 1BL:6D. Beetles wene checked at 24 h interva.l-s fon signs of panasitism. rn this trial, fon 12 panasÍtes, the average peniod for ranval developnrent, that is, fnom the time of nemoval of the host from cold stonage to pupation of the panasite, was 23.g days; the host died, on average, at 22.7 days (ta¡fe 4g). 4.2.3 Pupa upon completion of the ranval stage, M{¡iopharus sp. pupated within the exoskereton of the host. onty one pupanium was noted pen 276 Table 48. Time íntenval (days) fuom nemoval of su¡flower. beetle, 4ygogramma excramationis, fnom cord storage to death of EãeE, ani1iffiãã--"*"og"r".-oi ti," parasite, Myiophanus sp. S nemoval fnom col_d stonaee to Sex of Death o site Panasite host tion emengence Male Mean 20.5 22.0 36 .2 Þ..Þ. 1.4 1.6 1.3 Range t7 -27 t8-29 33-42 N 6 6 6 Ferrale Mean 24.8 õcn Qr! 41.2 1.0 1.0 0.8 Range 2t-28 22-29 39 -44 N 6 6 6 MaIe t female Mean 22.7 23.8 38. 7 S.E . 1.0 1.0 t_ .0 Range t7 -28 r8-29 33 -44 N t2 t2 t2 lReaned at 22 t toC. 2t7 Pa::asitízed beette. The pupanium was posítioned in a manner such that the antenion spiracres wene associated with the posteníor slit made by the maggot in the exoskereton of the beetle and. the postenÍor splnacLes were near the slÍt made between the Þr.othonax and rnesotho:rax. Myiophanus sP. energed fi:orn the poster.ion of the beetle. Daviaul-t (rg+r) noted the same positÍoning by M. donsaris on the wÍlrow r_eaf beetle. As stated pneviously, the n¡ean tirne fnom re'noval of the host fuom eold stonage to panasite pupation and emengence at 22 t 1oC was 23.8 and 38.7 days, nespectively (fa¡fe +e). Ihe mean dur.ation of the pupal pe::iod was thus 14.9 days. when the sexes r^ieï€ considened sepa::ately, the mean dunation of the pupal period fo:: the nnle and fernale was 14.2 and 1s.5 dayso nespeetivery. ïhis differ"ence was significant at the 0.05 level_. 4.2.4 Adul_t 4.2.4.1 Panasite ene¡"gence in the labonatory The peniod for" ranral and pupal development fon rares of Myiophan's sp. vras shorter: than fon females. fn a tniar where the developmental peniods of equar nunbens of nares and fernares were compared, the unr-es emenged after a ilìean of 36.2 days whe::eas the femal-es emenged aften a mean of 41.2 days (fa¡fe 4A). This diffenence was sígníficant at the 0.0S level-. fn labonatony, the aduJ_ts of Myiophanus sp. enenged appnoxi_ rnately one month after nonpanasitized beetles became sexualry active. 218 Nonpanasitized beetres broke diapause and stanted nating and raying eggs wÍthin eight to '10 days aften nemoval- from co.r-d storage wheneas panasite adults emenged fnom panasitized beetles a mean of 38.7 days after nerpval- frrcm col_d stonage. 4.2.4.2 Par^asite eael?gence in the field , !g77 A fietd tnial was cannied out in !976/77 to determine the tirne of emengence of the ovenwíntening genenation of Myiophanus sp. T\+o hr-rrdr"ed and fifty pnehibennation beetles wer"e co]lected fnom a sr'_ flowen fierd at Leter-lien, i'lanítoba, on septemben 3, 1976, and. wene imnediatery confined in five cages in a sum¡rer"fa1r_owed. fierd at the Agnícultune cana.da Reseanch station at winnipeg. The cages were galvanized metat cones 35 cm in diameter:, with two cir"curan opposing side vents 10 cm in diar¡eter, covered with 54 mesh sa'an scrleen. The cages wer€ remorred Octoben on Lg, J,976, aften alr the beetres had entezed the soír- beneath the cages to hiberrrate. on Apnii_ 18, rg77, energence cages wene placed over the same sites. These cages had a hexagonal- rnetal- base (+6 cm diamete::) with scr"eened sides topped with a netal collecting (Figurre can Bco p.57). The cages were checked daily frrrm Apnil 18 to June 22 fon emengence of adur_ts of the sr'frowen beetle and Myiopharus sp. rn addition, the 20 emergence cages fnom the study on the effects of snow cover on sunvival of the sunflowe:: beetle (section 4.1.1.3) wer:e checked fon emengence of MyÍopharus sp. seventy-four aduLts of the sunf,lowen beet]-e emerged. in the five emengence cages fnom May 6 to 22 with a mean enengence date of t"Iay 11, 219 r^rhe'eas 31 adults of Myiophanus sp. emenged. fnom the same cages fi:om June 5 to 1s with a mean emengence date of June g, 2g days raten than the sunflowen beetle (figur-e 26). Of the or"ígÍnal 250 beetles placed in the cages, onry 105 indíviduar-s (74 beetres and 31 panasites) on 42 peneent vrene accounted fon, with an incidence of panasitism of 2g.S pencent 0n1y two par"asítes wene corlected Ín the 20 ernengence cages used in the study on the effects of snow cover on overwinter ing sunvival of the sunflowen beetle, and both wene taken in cages whene the snow was left intact. The incidence of panasitism ín this study, based on emergence of hosts and panasites, was only 0.6 pencent. The pnobabre reason for the diffenence in incidence of panasÍtism between the two studies was that the source of beetles was diffenent. The beetles used. fon the snow coven trÍal wene corrected. on septemben 15 , tg76 fr.om a fierd at Rosenferd, whire the beetles fon the panasite emengence tnial wene collected september 3' 1976, fnom a fierd at Leterlien. 4 .2.4 .3 Mating Mating by ruryiophanus sp. was obsenved. in the labonatony on six occasions. vingin femaiesr less than 24 h old, wer"e intnoduced to cages containíng foun to fíve males which were síx to 10 days o1d. lfithin five to 20 minutes aften intnoduction, females wene noted in copura. No cour"tship behavioun was obsenved. pr:ion to males mounting females. using its fonelegs, the male gnasped the base of the wings of a female. Once in copula neithen mare non female moved. Mating rasted 0.5 to i_.5 220 Figur:e 26. Emer"gence of ovenwintened adults of the sunflowen beetle, Zygognamma excr-amationis, and ítfs panasite, Myiopharus sp., at Ìlínnipeg, ManÍtoba, tg77 40 a ¡ I I 35 |l ll lt tt tt tt ,ol tt o ¡¡+-tU¡tiopharus sp. (J I I I I c I I o ,rl I I I I I I o i ¡ I ¡ E ,al I I tu I Sunf lower I Beette i I I I c I I o ,rl I I o I ¡ L I I q) I I I I o. I I I I ! I t I I ,l I t tl I I tl I I .l ¡ t¡ I I tl I I ll I I fr I I t I I , 10 15 25 10 15 25 May June 22! houns' rt was not detenmined whethen mares or femares mated mone than once. 4 -2 .4.4 Lar"viposition successful- lanvipositÍon by the panasite on sr^frowen beetl_e adul-ts was not obsenved in the r-abor.ato::y, but some attnaction to the host was apparent' PosthibernatÍon beetles were routinery presented to parasÍte females kept in cages in the greenho¡se. The panasite woul_d sometimes criurb onto the donsar- su::face of the beetre and with its abdoren, pnobe arourd. the r-atenal edge of the erSrtna. on one occasion a beet]e dropped to the bottom of the cage forlowing what appeared to be an attack by a par"asite. The beetre appeareci to har¡e been ínjured. sÍnce one of its mesothor"acíc legs did not frrrction folLowing the encormter. No maggots, however?, wer?e forr¡d in on on the beetre d,ning a subsequent dissection' I'lyiophanus sp. did not show a simiran attnactÍon to rarvae of the sr¡:fl-ower" beetle. Díssection of mated femares nevealed. finst-instan maggots in line in a coiled utenus. Maggots neaï1 the postenior openÍng of the utenus had deveroped mouth-hooks while r¡aggots c.r_osen to the ovaries we::e less developed. Dowden (1930) described a similan arnangement fon the tachinid, Lyderla nigripes Farr-en. rn thr.ee fennles of Myiophanus sp. the mean number of rnaggots observed ' in the uterus was 65 with a range of 59 to 78. 222 4-2.5 fncidence of parasitism of adurts of the sr.nfrower beetle, 1975 to 7977 4.2.5.1 Pr"ehibernation beetles Collections of pnehibernation ad.u]-ts of the sunflowen beetl-e wene made during the fall- of each of 1975, 7976 and 1977 in surfl_ower fiel-ds in vanious locations in south-centnal- Manitoba to d.etenmine the incidence of panasitism by Myiophar"us sp. These beetres wene immedi_ ately placed in cord stonage and raten r.emoved. and sr.:bjected. to a diapause-br.eaking tneatment (Sectíon 3.1.1). Fecords wene taken of the numben of panasítes emenging fnom the beetles foll-owing cold storage. In these collections ' pencent panasitísm varied between veal?s, and between fierds within yeans, and ranged fnom 0.1 to 17.1 pencent (ra¡re +g). Fon exampleo in 1975 the incidence was 14.0 to 17.1 pencent whe:reas in 1977 it was onry 2.0 to 5.0 pereent, rn 1976n 15.3 pencent of beetres fnom one fiel-d was parasitized while only 0.1 pe::cent of beetres fnom a fiel-d six miles a!,¡ay was parasitized. The density of prehibernation beetres in the latten field was higher than ín the fo'nen and nray pantial-ly explain the difference in incidence of parasitism. 4.2.5.2 Posthibernation beetl-es Field collections of posthibernation adults were made du::ing the sp::ing of 1976 and rg77 to determine the incidence of par.asitism by Myiophanus sp. fhe beetles were maintained on potted sunflower.s in the labo::atony (section 3.1.1). As beetl-es d.ied, they were placed in 12 mr vials stoppered with a cotton-batting plug and examined dairy for evidence of parrasite der¡eloprrent. 223 percent Tabre 49. panasitism by Myiopharus sp. pnehibennation posthibe::nation of and. adutts-õEËãEunfiowen beetre, Zygognamma exclamationis, in south_central Manitoba, tgT'_,ffi-- Locatl-on;: '----- , Date- beetles 9o panasitized. Pnehibennation adults Rosenfel_d(2-g-1W) August 23, 1975 43 14.0 Rosenfetd( 2-g-1W) Septemben 5, 1975 I77 77 .7 Letellien( 11- 3-1E ) Septemben 3, 1976 346 Rosenfeld( 2-3-1t¡) 15 .3 Septemben B, tg76 772 0.1 Ste. Jean(R.t.257) JuIy 22, 1977 Ste..Tean(R.t.257) l_04 2.0 JuJ-y 29, 1977 B4 Lowe Fanm(10-5-1lf) 4.8 August 12, t9T7 100 5.0 Posthibennation adults Rosebank( 7-4-SW) May 28, !976 24 0 Rosebank( 7-4-sI,¡) May 31, 19 76 60 0 Ste. Jean(13-3-1E) June 1, 1976 60 0 G]enl-ea(R.L. Z, 3S4) June 7, ]-976 76 0 Rosenfeld( 2-A-1U) uTune 15, !976 60 0 Lowe Farrn(10-S-1W) June 21, 7977 60 Qâ 224 rn 1976, no adul-ts of lrfyiophanus sp. were r-eared from posthiben- natíon beetl-es collected in various sunflower: fields between lr{ay 2g and Jrrre 15 (ra¡re +s). rn 1971, tr"¡o aduJ-ts of Myiophanus sp. h¡eï,. rear"ed from 60 posthÍbernation beetres col_Lected on Jule 21 from a sampring plot at Lowe Farrn, Manitoba. The two panasitized beetles had died on July 15 and 18, respectivery, and the parasítes ernerged on July 27 and 30. 4.2.6 Numben of genenations per year Myiophanus sp. appears to have two generatíons per: year on the st¡1fr-ower beetle. The parasite overwintera as a fÍ::st_instar maggot in overwintening aduJ-ts of the sunf,Lowen beetre, kilting the beetl-e in the spr"ing before the beetl-e enìenges from the soil . l"fyiophanus sp. emerged approximatery one month after" nonpansitized beetres emerged. For e> 4 .2 .7 Hypenpar"asites Only one h5perpa::asite, identified as perilampus sp. (Hymenoptena:Peril-ampÍdae), was reaned. from l,fyiophanus sp. ït was rea'ed fuom a pupa of Myiopharus sp. that had developed in a prehiben- nation beetle collected septemben 3, !976, at Leterrier, Manitoba. This is the finst recond of a h54per.panasite being r"eaned fuom a Myiophanus specÍes. 226 4.3 Bionomics of Erixestus winnemana C:rawford, a pteronalid panasite of eggs of the su-¡flowe:r beetle 4. 3. 1 Labor"ator:y ::ea:ring Enixestus winner¡nna, a smarl wasp (Figune 24b, p.20g), r¡¡as finst neared fuom a coll-ection of srnflowe:r beetle eggs fnom Glenlea, Manitoba on July 2, 1976. Subsequent coll-ections from Glenlea provided mate::ial to stant a rabonatory culture and also pnovided data on the 'incidence of panasítism in the field. parasitized beetl_e e,qgs wel?e placed in glass vials stoppered with a cotton-batting prug and held in a growth cabinet set at 2s I 1oc and 16L:BD (section 3.1.3). par"asit- ized eggs would tunn or"ange compared to the usual- cneam-col-our of non- panasitized eggs (FÍgu::e 27). Near the end of the developnent of the parasite, the dank corour^ed body of the panasite coul_d be seen th::ough the chor"ion of the egg. Parasites enrer:ging frorn the eggs were supplied with a diet of liquid honey th::ough the nernainder. of their life cycle, 4.3.1.1 OvÍposítion fn the labor"atory, fenales of E. winnemana neadily oviposited in srrtflowen beetle eggs. fn the oviposition processo the female walked oven the e8gs, repeatedly pnobed them with her" antennae, and then pushed hen oviposito:: through the chonion presumabry to Ínject an egg. supenpanasitism was not conflìon, but two panasite ranvae were occasionally fotnd in a single egg, and on one occasÍon two pa:rasite pupae were found in one egg. Duning numerous ì-abor:atony neanings, not more than one adurt panasite was noted to energe fuom a panasitLzed egg. 227 Figure 27. Eggs of the sunfrowen beetre, Zygogramrna exclamationis panasitized by Erixestus winnemana ( x 14 228 In a labonatory trial, in 1977, Ínformation was obtained on the neproductíve pnocess, the preoviposition period, and the nate of developnent ¡nares of and feuales of E. winnernna. rn the tnialo 30 sun_ f,Lowen beetre eggs less than 72 h ord were exposed. for 48 h to a laborator:y culture of E. winnernana. FollowÍng the exposu:re period each egg was placed in a sepanaté 12 ml- viar stoppened with a cotton-batting plug and held in a gnowth cabinet set at 20 j tog and 16L:BD rn}til the parasites ernenged. Fonty-eight h aften the panasites emerged, and every 24 h theneaften fon thr"ee days, vingÍn fenale panasites togethen with 10 sr:nflowen beetr-e eggs ress than 49 h ord wene praced in !2 nr viars and returned to the 20oc ca-binet. Al_r eggs ex?osed were observed daily until either stmflower. beetle larvae or" E. winnemana adul-ts ererged' The sex of all the panasites that ernenged was d.etenmined by examinatíon of the genitalia r¡rder a low power dissecting micnoscope aften the parasites had been ptaced Ín 10 percent KOH solution for 12 h and compnessed between rnicroscope slides. l\renty-one panasites, 11 fennr-es and 10 nales, emerged fnom the 30 eggs onigÍnarty exposed to the laboratorlr cul_ture. lhe f_emal_es subsequently parasitized eggs introduced during the finst period of exposune- The preoviposition peniod fon å. winnemana was thus ress than two days at 20oc. sÍnce the fenales had not mated, yet progeny were pnoducedo E. winnenana is capable of repnoducing parthenogenetic- al'y. Howeven, arilueny were males. 229 4.3.1.2 Rate of development of mal-es and females ïnfonmation on the r"ate of deveropment of the sexes vras obtained fnom data genenated in the oviposition study. The 11 femal_es emerged 15 (mean, to 19 16.4) days aften the sunflowen beetle eggs had been exposed to panasites the whire.the 10 mar-es emenged 16 to 19 (mean, 16.6) days after the host eggs were e>çosed. These r"ates of developnent were not significantly different. 4' 3.1.3 xate of developrent at vanious constant temper"atunes fn 7977, a labonatory t::ial was set up to deter.rnine the r^ate of development of E. winnemana at vanious constant temper.atur.es. The data fuom this tnial were used to detenmine the lower thr"eshoLd temperatune (ToLo) and thernnr r'it r-equinements (TUrs) of the panasite (section 4. 3.1.4). Two hr'dred and ninety sunfr-ower. beetr_e eggs, r_ess than 4g h oId, were e>posed to a laborato:ry cu-l-tu:re of E. winnemana fo¡ 24 h. Following the exposr:re, the eggs were divíded into gnoups of 10 and placed in t2 ml vial-s stoppened with cotton-batting. Ten vials were placed in each of two controlled-envinonment cabinets at 20 t 1oC and 25 t 1oc, r€spectively, and nine vials were praced in a cabinet at 28 1 1oc. The photopeniod was 16L:BD for arr- cabinets. vÍars were checked every 24 h to d.etenrnine par^asite ernergence. At 20, 25 and 28oc the mean tíme from exposune of host eggs to emer?gence of the pa'asite was 16.1, 10.g and 7.9 days, r.espectivery (ra¡re so). By compa:rison the incubatíon per"iod fo:: surfrowen beetle 230 Tabl-e 50. Days nequir"ed to compJ-ete development of the panasite , Erixestus winner¡nn?, on eggs of the sunflowen beetle, Zygogramna excGnìa.tîontg, ãi trr*e teïnperatures 20 28 16.14 ! O.ZS 14- 19 25 40 10. 83 t O. rt 10- 14 28 23 7.91 t 0.15 7-70 rDu:r'atíon fnom the day host eggs r^rere e>posed to E. winnemana to the day E. wínnemana ener"ged as an adu1t. 23t eggs held at these temper"atures þras 7.g, s.6 and 4.5 days,.nespec- tively. Daviaur-t (1941) reponted. a deveropmentaÌ peniod of 11 to 18 days for" E. winne¡rana reared at room tempenature on eggs of wir_r_ow l-eaf beetle' i"lullíns (tszo), wonking with E. winnemana on cal-lignapha spinaeae in vir"ginia, reponted a deveJ-opmentar tinne of seven days when reaned at room tempenatu:ne. 4.3.1.4 Estimated ToLO and TU ::equir"ements Results fuom the constant tempenatu'e tniar- wene used. to estirnate T.LO the and Theor"eticar ru requirements fon E. winnemana. rre estinated rolo for the life cycr-e of E. winnennna was t2.4oc. This val-ue was cal-culated fuom the equation for. the nate of development wher"e Y = -0.0926 + 0.007gX, wher"e X = tempe:ratr::le in oC 7 Y r'ate of deve.l-opnent (i.e. = @) at tempenature X. The r"2 fon the line was 0-969- By companison the T.LO fon the egg stage of the sun- f'owen beetre g.goc was (section 4.1.5.3). These nesults agnee wÍth those of othens which show that panasítes have a highen ToLO than their. (Campbell hosts et al 1974; Johnson et aI 1979). The Theoretical TU nequinements for the tíme to emer gence for- E. winnemana was 127. llith a knowledge of the ToLO and TU r"equinements, estímates of the seasonar occunrence and number^ of, genenations of the parasite can be made (Section 4.3.4). 232 4 rncidence '3 '2 of panasitism of eggs of the sunfrower beetre colrected in the field 1976 to í1977 Following the first neaníng of E. winnemana fnom sunflowen beetl-e eB8s, in 1976, peniodic fieLd col-lections were made to dete::míne incídence of panasitism. The maín source of host eggs h,as fr.om the oviposition studies at Glenlea, ManÍtoba, in 1926 and 1977. rn this studyo beetles were moved to fnesh plants eveny second day and eggs laid dtrling the peniod' wene left in the field fon a fu¿"then tr^ro to six days befone being taken to the labo::ato::y. rn 1g76r eggs wene eollected fnom JUJ-y 12 to 26, and, in 1g77, from June 23 to JuIy 5. colÌections of sunfrower" beetre eggs wene also made , in rg77, fnom sampling plots at ste. Jean and Lowe Fanm. Random samples of eggs wene taken fnom prants adjacent to those in plots used. to study the bionomÍcs of the s'nfrowen beetle. Eggs wene corrected. at ste. rlean fnom May 24 to Jture 17 and at Lov¡e Fanm fnom June 3 to 28. The incidence panasitism of for eggs collected at G1enlea narrged from 43.3 to 65.7 pencent, in !976, wher.eas the incidence nanged fnom 0 to 58.0 pencent, in 7977 (Table 51). The incidence of panasítism tended to incnease in the raten samples suggesting a buird-up of the panasite. E. winnernana panasitízed fnom o to 16.g pencent of the eggs collected fnom the sampring prot at ste. Jean and. fuom 0 to 3.g pencent of the eggs collected fnon the Lowe Fanm plot (Table 52). Incidence of panasitism fon both the ste. Jean and. Lowe Fanm plots was thus genenarry 10wer" than that obsenved, for. Glenlea in 1g76 and 7977. These differences may be due to diffenences Ín dates of corlection. The Grenlea 233 Tabl-e 51. Percgnt panasitísm by Erixestus winnemana of esss of the surflowe¡ beetre , zygoFlñiË-Eiamaffi;ñ, .oiï"".ã¿ .. Glenlea, Manitoba Date Pencent panasitize d 1976 July 8-10 JuJ-y 12 110 JuJ-y 58.2 10-12 JuJ-y 14 ôt 43.3 July 12-14 July 19 70 JuJ-y 6s.7 14-16 Juty 21 ,34 47.7 Ju-ì-y 16-18 JvIy 22 104 61. 5 July 18-20 JvTy 22 107 57.9 Jvly 20-22 JuJ-y 26 89 61.8 7977 Jrne 15-17 June 23 57 0'0 Jr.me 17-19 Jr.ne 23 B8 ¿.ó Jr:ne 19-21 Ju-re 23 160 ó. r Jr:ne 21-2 3 Ji:ne 27 2I0 3. / Jure 2 3-25 June 27 163 Jl'¡:,e 25-27 4.9 June 30 172 26.2 J:g;.e 27-29 Jr:ne 30 9B 37 .8 June 29-Juty 1 q July 94 27 .7 July 1-3 tr .Iufy J 302 58.0 lData obtained fnom an ovÍposition study whene egg-laying hosts were moved fnom plant to plant at two-day intenrrri". eTotal numben of panasítes and sr:nfl-owen beetle collection. .l-arvae emenged from 234 Tab1e 52. Pencent panasitism by E::ixestus winnemana of eggs of the s unflowen beetle, zygoþããñiIcra-ffim; . collected f::om ---Ê! two sur¡flowen fielasffitoba,-.:- tg77 Percent Collection date Number2 sitized Field 1 I'Iay 24 77 9.1 I[ay 27 tot 16 .8 May 31 - 52 13 .5 June 3 53 June 15 .1 10 22 4.6 lïune 14 43 0.0 June 17 77 ol FieÌd 2 June â 203 3.9 Jur¡e 7 367 June 3.1 10 t0t 0.0 June 14 132 June 0.8 t7 116 0.9 Jtme 2t 722 1.6 Jule 24 65 3.1 June 2B 67 3.0 1Field 1 - ste. Jean, Manitoba, (River" lot 257) Fie1d 2 - Lowe Fanm, ManÍtoba, (10-s-1rI) zTotal number of panasites and sunflowen beetle collection. lanvae emenged f::om 235 collections lJere made late in the summen; E. winnenana may thus have had urone tire to build up. In t9?7, egg-laying was.al-most complete at Ste. Jean (Tabte 29, p.156 ) and Lowe Fanm (Tab1e 30, p.159) when collections wer€ started at G1enlea (talte St¡. (1941) Daviault ptrbrished the only information in the incidence of panasitism by E. winnemana. He neponted that in Quebec, the incidence parasitism of of eggs of the wilÌow leaf beetl_e nanged frorn 26.5 to 63 per"cent duning the yeans 1934 to 1936. 4.3.3 Overvrintering and spning emengence The overr,¡intering stage on r-ocation was not dete'mined, but it appeared that E. winnenana did not over.winter in association with the sunfl-owen beetle. lhis is based on the obsenvation that no diapausing stage of the parasite was deteeted in any field coll-ections of su-rfl-Qwer beetle eggs non was diapause detected in raboratony cultures. Labor"a- tory tnials aimed at inducing dÍapause, or fierd cor_r-ections of alternate hosts rate in the season would be nequined before speculation on ovenn¡intening could be nade. spning emergence of E. winnemana appeaned to be in good syn- ehr"ony with that of the stnflower. beetle o at leas t in !g77. Sunflowen beetle eggs l¡ene finst detected in the field on May 17 (Tabre 13, p.1og) and E. winnemana was noted panasÍtizing eggs in a sr'frower fierd at ste- Jean, I'4anitoba on r"ray 24. The incidence of panasitism fon eggs collected from that field on May 24 was 9.1 pencent (Table 52). 236 4.3.4 Numben of genenations per yean An estimate of the numben of genenations pen yean was mad.e on the basis TU of nequinements for one complete genenation. As noted, r27 TU's (t2.4oc ToLO) v¡ere nequined fon d.evelopment fi:om the time sunflov¡en beetle eggs wene panasitized until adults of E. winnemana emenged.. The preoviposition peniod at 20oc was less than tv¡o days so an estimate of the TU requinements fon a complete gener.ation wour-d be r42 TUrs (12.4oc ToLo) ' rn !g77, sunflowen beetle eggs r^rene finst noted lrlay 17 and last noted in a commercial sunflowen fietd on July g (Tabl-e 13, p.j_03). The TU accumul-ation dur'Íng the connesponding peniod would have been 299. This estimate was based on daíly ain tempenatune data obtained fuom the lleather station at Monnis, Manitoba, and with the chmiel and wÍrson modification of the sevachenian method of TU calcuÌation (section 2.5.1-2). Thus, in i-977, E. winnemana courd have compr_eted two gener:a_ tions and possibly stanted a third. Not n¡one than two genenations of E. winnemana would have developed in the commencial sunflower. fíelds sampled ín rg77. For" exampre' at ste. Jean, sunfrowen beet.l-e eggs were noted fnom May 24 to July 1 (table 29, p.156). The conresponding TU accumuration was 194, so one complete genenation could have devel0ped and repnoduced to pro_ duce a second genenatíon. The finst new-geneï,atíon par"asites coul_d. have emer:ged and stanted ovipositÍon by Jwte 22, howeven, by that time relatívely few sunflower- beetre eggs v¡ere reft in the fiefd (Tabre 2g, p.156). similanly at Lowe Fanm, sunflowen beetr-e eggs þrene obsenved from June 3 to July 8 (Table 30, p.1S9) duning whÍch 200 TU,s were 237 accumulated. The first nevù-genel:ation parasites coul-d have. emenged and stanted oviposition JuJ-y by 1, but by this tine the number" of eggs was rapidly deerining (Tabr-e 30). Data fncm field corrections of eggs fnom both (Tabre prots 52, p.234) tend to suppont a two-generation theory. A high incidence of par.asÍtism nean the end of the egg-raying períod of the host would suggest oviposition by new-generation parasites. The high par"asitism nates noted in the Gl-enlea plot duing July (Table 51, P'233) *y have been fon this reason. E. winnemana may have arten-rate hosts fon late season deveropment, but no studies were initiated to detenrnine alternate hosts in l,fanitoba. 4. 3. 5 H5penparasites No hyper-panasites r^rene reared. from E. wínnemana. 238 4.4 Bionomics of Dor-5¡phor"ophaga nncel.l_a Reinhand, a tachÍnÍd parasite of larvae of the sunfl-owe:: beetle 4.4.1 Rearing in the labonator"y D' rnacel-l-a was successfully rear.ed thnough three consecutive gene::ations in the rabonatoïy. Reaning was cannied out by, fir.stry, collecting parasitized l-anvae fr.om commencial sunfrower. fields to Ínitiate a labonatory colony. Adutt panasites neared fnrm these rar"vae we:re placed in cages in gnoups of 50 to 200 and fed a mir_k-sugan_water diet (section 3-1.4). Gnoups of 20 laboratony-neared rar.vae of the s'nflower beetre were exposed to the parasites for one to two h peniods and subsequentJ-y maintained in the labonatory until the new-gene¡ation panasites emerged. The cycle was thus completed. Obsenvations on mating, Ia:rviposition and development of D. macella were made on the laboratory colony. 4.q.1.1 Mating Although hundreds of parasite acul-ts $rer€ reared in the l-abo::a- tony, mating r,¡as obsenr¡ed on onÌy two occasions. Dr:r,ing these bnief obsenvations no countship behaviour was noted. The males simply mor:nted the ferqfes and the pain then appeared notionless. 4.4. 1.2 Lar"viposition D. macerla berongs to a grrrup of tachinids known to panasitize by prnctu::ing the integument of thein host with a cunved spÍne_like abdo¡nínal piercen carled a steïnotheca and depositing a fir^st-instar" rnggot through the opening by means of a closely associated, but 239 separate ]-anvipositon that slides along the ster_notheca (Townsend tgt2). va::ious dissections and tnials were cond.ucted to deter"míne whethen or not D. mace.l_Ia has a similan repnoductive biolory. 4-4.1-2.1 Arignnrent of fÍnst-instan maggots in the ute'us A sample of females of D. mace.l-Ia ï/as renìoveC fr^om the l-abora- tory colony and dissected to determine the state of devel-opment of the repnoductiv.e pnion system. to kílr-ing the fenares, they wene praced in cages wÍth gnouP a of 10 laboratony-reared l-ar"vae of the sunfl-ower^ beetle fon 24 h. obsenvations r¡rere made on whethen rarvae wene attacked and whethen maggots were for:nd in the ranvae folrowing the exposune peniod. Approxinntery 100 to 300 furry deveJ_oped finst-instar maggots were for-u-rd in the utenus of panasites that had successfully parasitized their" hosts' The naggots were arigned in singJ-e on d.oubre fil-e inside the long coired utenus of the panasite. Deveroped mouth_hooks were clearly visible in maggots r-ocated nean the poster:ío:r opening of the uter"us, wher"eas maggots funthe:: away fnom the opening had tess distinct mouth-hooks on no mouth-hooks wene visibr_e. rt wour-d appear that the panasite egg deveJ-oPs as it passes thnough the uter"us of the parasite and that a furly deveroped first-instar maggot is deposited. tfaggots recovered fnom larvae e>çosed to the parasites had mouth_hooks of the same size and shape as those obsenved. in the utenus, thus, indicating that no mort had taken prace immediately pnior to or" 24 h aften ranvi_ position- The sequential- deveropment of maggots noted withín the uterus arso wourd suggest that maggots may be deposited ove:: an 240 extended period nathen than simultaneously. Townsend (tgtZ) noted a similan arrangenent of maggots in the uter.us of D. donyphorae. No ref- enences wer.e found in the litenature on the neproductive bio}ogy of D. macella. Sonre of the D. macel-la females taken firom the labor.atony colony were found to contain up to 300 regg-líker ':rdeveloped stnuctures ::athen than finst'-instar- maggots. These females had been noted attack- ing ranvae, but no maggots were necovened. fnom the hosts. Al1 females ín the sample were at r-east 10 days old, thus, it was assun¡ed. that the pnelanviposítion per-iod had been completed (Section 4.4.I.2.g) and that this was not the reason for" the l-ack of developnent. The most probable reason, howevei" was that these fernales were unmated. This statement based is on the obsenvation that natings r^rere narîery seen in the labor"- atory, that no developnent was noted. within the 'regg*l-iker stnuctu::es in the uterus and that no offspring were pr.oduced. 4.4.7.2.2 Behaviour. duning lar.viposÍtÍon Obsenvations on the behaviour of D. macelra dr:ning the act of lanviposition were made when l-ar.vae of the sunfl-owen beetle wene e>çosed to the parasite to estabrish a labonatony cur-tu'e (section 3.1.4). Duning the pnocess of ranviposition, the panasite genenarly landed on a plant and mor¡ed quickly oven the l_eaf su¡face and aror.nd the stem appanently in seanch of a host (Figr:re 2Ba). Sometimes the panasite woul-d walk past a l-ar"va without stoppingo whíre at othen times it would clinb onto the donsaf- sunface of the larva contacted.. once on the lanva, the pa::asite positioned Ítserf at an angre of g0o to the 241 Figune 28. LarvÍpositíori sequence of Dor"yphonophaga macelra du::ing panasitization of lar"vae of the sunflower beetle, Zygognamma exclamatignís (A) panasíte seanching fon a host l_anva ( x 2 ) (B) panasite str.addling a host l-arva ( x 2 ) (C) panasíte injecting maggot a into a host lar.va ( x 2 ) 242 lar"va (Figune 2Bb) ' arched its abdonren and with its shanply pointed sten'lotheca pLu-rÇtuned the lateral- anea of the abdonen of the host rar"va (Fígune 2Bc). Then, presumabry a finst-instar- maggot was imne¿iatery insented thnough the hole in the cuticre by means of a r_anvÍpositon. ThÍs latten openation was not discernibl-e duning the attack. At the time of the prrrctr:::e., the host rarva often neaned up and foncefurly defecated on its own back, usualry missing the panasíte in the pnocess. the panasite 'Aften withdrew from the host, it walked away to undertake what appear^ed to be a groorning sequence. The par.asite cl-eaned its front legs with its mouth parts and with its hind legs stnoked its abdomen. sometimes the panasite wour_d dr.ag its abdomen arong the edge of a l-eaf. occasionarry a parasite wour-d return to the parasitized .l-anva and feed on haemolymph escaping fuom the v¡ound. The above behaviour was modified when smarr host ranvae were attacked' rn this case' the panasite pnobed r^rit-h its abdonen among the l-eaves o' br"acts at the growing tip of the prant until_ a r_ar.va was located and pienced. The parasite did not cr_imb onto the r-anva pnesum_ ably because the lanva was too snnl_I. 4.4. 1.2. 3 Fecundity and lanviposition per"iod A triar was set up Ín the 1a-bor.ator"y, in 1976, to d.etennrine the fecr'ndity and duration of the ranviposition peniod of D. nncella. Nine femal-es, five to eight days oJ-d, were taken fr.om a stock cultune, and each placed in one of the standand neaning cages, a prastic cyJ_inden measuning 10 x 25 cm wíth 54 gauge nyron cl-oth oven ventiration holes at the sides and (Figur.e top 3a, p.S7), togethen with 10 finst_ on 243 second-instar larvae of the sunfrowen beetle on a two to fou¡ l-eaf srnflowen her-d 50 Ín a mr Enrenmeyen fr-ask containing tap water. Food, consisting of a sugar-mi1k-water sorution, in a t2 nL vial with a cotton v¡ick was provided (section 3.1.4). A1l reaning hras conducted in a contr"olled envinonment chamben set at 22 ! 2oc and 1gL:6D. At 24 h intenval-s each femare was t::ansfer-:red to a f::esh cage wÍth new host lanvae. rhe exposed rarvae vrere preser"ved Ín 70 percent ar_cohor_ and the incidence of pa::asitism detenmined later. fnon sride prîeparations viewed unden a low-power disseeting mic::oscope (Sectíon 3.3.g). The nine females deposited a mean of 2g4.6 (r.ange, 152_43g) naggots each over a pe:riod of 14.2 (r.anger 10_1g) days (Tab1e 53). The mean daily production (r"ange, was 19.6 15.2_26.0) maggots with a maximum of 60 rnaggots being ::econded fon a singre femare oven a 24 h per"iod. Maggots were deposited ar-rnost every day of the la'viposition pp:riod including the finst day larvae wer€ ex1>osed, thus, the preranvi- position peniod was five to eight days on less. All_ females produced maggots r:ntÍI two days of death. super-panasitism was cormon in the tniar_ wíth a record high of 32 maggots being recovered fnom a singÌe host. A numben of host rarvae were dead at the end of the 24 h e>posure peniod pnesunnbÌy f:rom nepeated attacks of D. macerla. Despite the high nate of lanviposition by individr:al par:asites, only 57.4 (r"anger 40.6-72.0) pencent of the host la'r¡ae exposed dur"ing the tr-iar Ì¡ere pa'asitized (Tabre 53). Folrowing the death of nine femares, they were dissected and the reproductive organs exam:ined. Each fennl-e contained. between 50 and 2+4 Table 53. Lanviposition per.iod., total and. mean daily pnoduction maggots of by Donyp_horophaga macel_Ia. and pencent pana- s itism or rinsîräfrãGãriffiFTárvae of the sun- flower beetleo Zygogr"amma excl_amatíonis 1 peniod .-*l -Tãïril - host tanvae Female2 (days) Totar Gãn Tff:JRange par-asitized t 18 304 16.9 t 2.4 o_32 2 s8.3 71 205 18.6 I s.6 1_48 40.6 3 77. 438 ZS.e i z .a rc_47 68 . 1 4 1s 403 zz.+ E ! s .o 2_st 72 .o 13 270 16.2 J 3.6 t_42 6 50.8 10 173 17.3 t 5.6 o_58 44.6 7 14 364 26 .0 t 5.0 0_60 I 77 372 62.0 I 18.4 t 3.4 5_48 61.1 ______19______1!2 Ls.2 ! 2.8 4_31 s8 .7 Mean 14.2 284.6 19.6 t 1.4 57.4 lLar"vae exposed to panasítes daily Ín gnoups of ten. 2Reaned at23+ 1oc,16L:BD. 245 119 (mean, 73) paï'tiall-y on fully derreloped maggots hrithin .the utenus. The potential maggot pnoduction wourd thus be g::eater than that neconde d. In 1976, a labonatory tnial was set up to detenmine whether" on not thene was a dífference in incidence of attack bv g. rnacerra among instars of the sr:nflower beetre. Ten individuats of each instar wer€ exposed in cages to fou:r females of g. macella for a 24 h períod. Following the e>çosure, the four females wene tr"ansfenred, on each of two occasíons, to fresh cage a containing 40 lar"vae; a totar of 30 individual-s of each instar wene thus exposed. rmmediately fo]_lowing each exposur€ ' the host lar:vae were pnesenved in 70 pencent alcohol for subsequent detenmination of the incidence of panasitísm. Maggots were necovered from lanvae of alt instans, the incidence of panasitism beíng 36.0, 44,g, 87.5 and 60.5 percent for the fÍ:rst-, second-, thir:d- and fourth-instans, respectiveJ_y (fa¡fe S+). Super_ panasitism vÍas comnon with !.22, 1.38, 4.00, and 4.3g maggots, respectívely, fourd in panasitized lar:vae of the first- to four.th_ instans ' the l-àten instans r.rere noïe heavily attacked than the eanty instars, but npre extensive tniars wour-d be requined to determine whether" the late instans wene prefer-red. or whethen they were just mone accessible than the eanlien instans. Maggots of D. mace.l-la were dissected fnom lanvae in al-l- instars col-lectecl fr.om the field; these ::esul-ts will be dealt with in detail later (Section 4.4.2.5). Kellehen (rg0o) stated that D. do¡yphor:ae attacked thind-, and four"th-instan lanvae of the colonado potato beetre, but did not indicate whether fínst-, or second-instan lanvae were examined. 246 Tab1e 54. Incidence of panasitísm and degree of supenpanasitism by Ponyphonophaga nncell a among fir.st_, second-, thir:d- and fóu::timstan tã::vå,e ãr the sunfl-owán beetle, Zygog::anrna exclarntionis Ín the labonatony L1 25 36 .0 1.22 o.22 L2 t 29 44.8 1.38 t 0.18 L3 24 87¡5 4.00 t 0.55 La 38 60.5 4.39 t 0.77 lThinty host l-arvae of each instar- exposed for 24 h to fou:: pa::asites. The numben lanvae. of of each instar necover:ed forrowing the exposure was not equal to 30 because some l-anvae had peníod molted aunlng tne ä+ rr and fou:: of the 120 la::vae were not recovened. 247 4.4.1.3 Larval (nnggot) stage 4.4.1.3.1 Numben of instars D. macerla passes th*ough th::ee instars which can be distin_ guished fuom one anothen by a companÍson of the size and shape of the mouth-hooks (Figune 2g). The mean length of the mouth-hooks of the finst-, second-, and thind-ínstan was 0.1g8 1 O.OOO mm (T t SE); 0'300 t 0'005 mm, and 0.6gg J 0.00s rmn, nespectively, based on measu.ne- ments of 25, 5 and 25 individ'ars. The fir.st_ínsta:: naggots of D. nn'cella and MyÍophanus sp. can be distinguished fr"om each othen by a companison of the size and shape of the mouth-hooks (Figures 25, p.2!2, and 29). 4.4 .!.3.2 Lar"val development Maggots of D. macella do not devel0p beyond the finst_instar until nean the end of the larval stage of the host. only finst_insta' maggots were found in host ranvae of the finst th:ree instans. second_ ínstan naggots wene found in up to 1g percent of parasítized for::rth_ ínstan lanvae colrected fnom the fie1d, whír_e onry finst-instar. maggots wene found ín the nernining 82 to 100 peneent of the founth_Ínstan lanvae. Finst-instan maggots spent the eanly par^t of their devel0pment fnee in the haemocoer of the host. They were not associated with a panticular organ' nor did thene appean to be any attachment to host tr"achea. Foll0wing the f::ee lÍving stage, some fi::st-instar maggots fonmed a nespinatony funnel- which was associated wíth, but not attached 248 Figune 29. Latenal view of nouth-hooks of finst instar maggot of Donyphor.ophaga macella (725X) 249 to, the abdomínal spiracres of the host. Respinatony funnels were found ir¡ second-, thind-, and founth-ínstan hosts. Fon example, in sampres taken at ste. Jean fuom June 24 to Jury 22, 1975 (section 4.4.2.1), 0.0, 7.4,15,3 and 44.2 pencent of the parasitized finst-, second-, thind._, and fourth-instan host lanvae had D. macell-a nespinatony funnels. The timing of the fonrnation of the nespínatony funner by first_instan rEggots waso thuso va::ia-ble. second-, and thind-instan maggots wene always noted with a respinatony funnel. l*laggot development l¡as napid once a panasitized host compJ_eted the fou::th-instar. and entened the soir to fonm eanthen chambens. For exarnple, 20 par:asitized lanvae::eaned at 25 l loC wene kil1ed by devel-opÍng maggots a mean of 2.3 (nange one to fou::) days aften they entened the soir and in a further. one to two days, D. macella pupated. PanasÍtized' host did not deveJ-op beyond the pnepupal stage. g. macerla, thus, compreted the second- and thind-instars in a mean of 4.1 (nange, two to síx) days of the time that panasitized hosts entened the soil-. Kellehen (rg0o) noted that D. donyphonae killed the colonado potato beetle <ì'ning the pnepupal stage and that the panasite pupated about six days afte:: the host enter.ed the soil_. 4.4.1.4 Pupal stage D. nacella pupated within the nennants of the host cuticle (rígune 24c.. p.209). pnion to pupation howeven, the thir,,r-instan maggot rnade two openings in the cuticle of the host; an anterion ventnal_ opening between the fonelegs and a posterior openi.ng near? the anus. 250 of 100 parasitized hosts examined, 80 panasite pupania wer.e oniented in a n'nnelr such that the antenion spinacles were associated with the postenior" opening and the postenior spiracl-es wíth the anterior. opening. The remaining pupar:ia were in the reverse position. Al_though super_ panasitism occunred, only one parasite pupated and subsequentJ-y emer"ged frorn any one host. the duratíon of the pupal stage was deter.mined fnom individual reanings of 20 parasitized (Section hosts 4.4.1.A.2). At 25 t 1oC, the pupal stage lasted a mean of 10.3 days with a range of nine to 72 days. D. racell_a adults, thus, emenged 14.3 (nange, 12 to 17) days aften par"asitized l-anrae entened the soil . Effects of sex and. temper:ature on the nate of development and emengence of D. macer-r-a wir] be discussed in the following section. 4.4.1.5 Effect of dÍfferent constant temperatures on rate of deverop_ ment rn 1977, a rabonator^y triar was set up to deter"mine the effect of diffenent constant tempenatures on the rate of development of mal_es and fennres of D. macelra. Lowe' thr"eshord temper.atures (T.LO) an¿ Theoretical thenmar- unit nequirements (Theor^. TUls) we¡e careu-r-ated using data from the tr.ial-. La'vae of the sunfr-ower beetle parasitized in the fier_d were used as a source of D. macer-Ia fon the constant tempenatune tniar. on Jure 30, !977,800 lanvae in the late founth instar were colrected from srrrf-lowen prants in a fierd at ste. Jean, Manitoba, divided into groups 25t of 25 and pÌaeed ' in each of four controlled environment cabinets at 15, 20r 25 and 28 1 1oc, nespectively. At 24 h intenvars, emerged host and panasite adults were removed and pz,esenved in 70 peïcent alcohol. The sex of the panasites was subsequently determined by an examination of the abdonen, with a micr"oscope, for"'the presence on absence of a sterrrotheca for.u-rd olirly in fernales. 4.4.1.5.1 Rate of developrent of males and femal_es At thnee of the foun rear"ing tempenatunes tested, adult rnales emenged significantly eanlier^ than females. At rs, 20, 25 and 2goc, the mean tine of emergence fon rnar-es was 42.4r 20.41 14.6 and 11.2 days, nespectively, aften the lanvae wene col-lected while that fon femal-es was 46.6' 23.8, 14.5 and 11.7 days (Tabre 5s). The nate of devel_opment r^ras significantly diffe::ent (p < 0.05) between sexes at each of 15, 20 and 28oc, but not so at 2soc. lfhen sex was not taken ínto considenation the mean time of eme'gence at the four tempenatunes was 44.r) 27.2, 14.6 and 11.4 days, nespectively, after coilection. Kerlehen (tgoo) reponted that D. dor5æhonae emenged fuon field-collected larvae of the colorado potato beetre in 19 to 32 days when neaned at noom ternperature. Kellehen did not dete¡'rnine whether rnal.es and females had differ.ent development times. 4.4.1.5.2 Rate of developnrent of panasite and host Development of D. macella was napid and adults of the panasite and non-panasitized beetles emenged alnost at the same tirne . At 20oC, panasites emerged an average of 1.1 days laten than the beetles whÍIe 252 Table 55. Developmental tíme (days) for males and females of Donyphonophaga macel1a, at foun tempenatunes Tempenatune Dunationt (dqys) of ¿evetopment for: (+ 10C) 15 Mean 42.38 46. 56 44.09 S.E. 0.74 1.25 0.79 Range 40-47 42-52 40- 52 13 9 22 20 Mean 20.22 23.75 C1] 22.24 0.31 0.46 0.40 Range 19-24 18-29 t8-29 N 18 24 42 25 Mean 14.64 14.52 14. 56 S. E. 0.77 0.19 0.26 Range t3-21 L3-17 t3-21 N tt 2s 36 28 Mean tt.t2 !7.72 11 .43 S.E. 0. 33 0.24 0. 14 Range tt-72 11-14 11-14 N t7 18 35 lDunation fnom the day fou¡th-instan larvae of the sunflowen beetle wene collected in the fíe1d tilt the day panasite emenged adults 253 at 25 and 28oc, panasites energed an aver?age of 0.5 and 0.g days eanlien than the beetles. No record.s of beetre emergence wene taken at 15oc. Kellehe:: (rg0o) noted that when reared. at rrcom temperaturc, D. macer.l-a emerged appnoxinatery 2.0 days aften nonpanasitized adu-r_ts of the colonado potato beetle, whereas D. dônypholae emenged 6.3 days aften the host 4.4.1.5.3 Estimated ToLO and TU nequinements Resul-ts from the constant tempenatu:re tnial (Section 4.4.1.5.1) were used to estinrate the T.LO and ruts for development of D. macerl_a fnom nean the end of the finst instan of the nraggot to adult emergence. Ttre estimated roLO for mar_es and femar_es of D. macelra was 10.2 and 11.0oc, respectively (ra¡re so). By comparison the ToLo for the srnflowen beetle was 7.4oC (Section 4.1. g.2). These nesu'ts confi::m those of campbell- et al 1974 and Johnson et a.r- 1929 that parasites have a highen ToLo than thein hosts. Note that the tolo ron E. wínnemana was also higher than the ToLo fon the egg stage of the sunflowe:: beetl_e (Section 4.3.1.4). The varues for Theon. TUrs requined for deveropnent of mares and femal-es of D. macer-r-a were 204 anð.202, r,espectÍvely (raute so¡. the developmentar peniod ::eferned to wour_d be from the nid peniod of the fou:rth Ia::var instan of the host (i.e. nean the end of the finst instan of the panasite) untíL the emengence of the parasite. the tor,o and rheon. TUrs fon D. macerra negardress of sex was 10 . 6oC and 20 3 , r"espectively ( fa¡fe SO ) . 254 Table 56. Regressioir equations, coefficients of d.etenmination, estimated thr"eshold tempenatunes (ToLO), and tf,.ã"Lii..f thenmal r¡nít (Theon. TUrs) nequinements fon ¿evefof*urrt, of mal_e and female Do:nyphoooph"g" macella Regnession ê9uation2 r g (Y=a+ determination TOLO Theor. a bx (n2) (oc) TUrs male 05002 -0. + 0.00490X 0. 9gg 10.2 204 female 05421 -0. + 0.00494X 0. 996 11. 0 202 combined 05231 -0. + 0.00492X 0.995 10. 6 203 lDevelopment from th" d" . tirl the day panasite adultsLe emenged.ç¡¡¡e¿ zALl,iii"..:î:1:":::-ï,rl: values ¡o'nded to fiveIlurd places È;ç 3Y = necÍpnocal of numben ofldays, oC avaLues X = tempenatune in ane fr:om the negnession equation näunded to the near"est unit 4.4.2 255 Pa:rasitism of sri¡rflowen beetre rarvae by D. rnacella in field_ samplíng plots sr¡r¡fl-ower" beetre larvae coll-eeted twice weekly throughout the gr"owing season from sampling pl0ts at ste. ,Jean, in 1g75, Letellíen, Ín 7976, and Lowe Fanm, ín tg77, Íreï€ pr.esenved. in 70 pencent arcohor- and subsequentry examined to deternÉne the incidence of panasitis, by 9. rnacella (Sections 3.4, 3.4.10 0.4.2 anò 3.4.4). The incidence of panasitism and superPallsÍtism of each of the four lanval Ínstars of the host was obtained fon each sampring date and this data to deten_ 'sed mine the bionornics of D. rnaceLla in the fie1d. 4.4.2.7 Ste. Jean, 1975 rn col-rections of finst-, second-, thind-, an. founth-instan larvae of the sunflowe¡- beetle at the ste. Jean ptot f.om Jr'e 17 to Jvry 22' 1975o the rnean incidence of panasitisn by D. macer_la was 52.8, 72.6,75.7 and 71.9 pencent, nespectively (Ta-ble 57). No panasitized l-arvae wene taken in the plot untir- Jr:ne 24, arthough the finst host larvae were fo'nd on June 17. sampling was tenrninated after Jury 22 because the coope::aton accidentarly appried insecticide to the prot whil-e spnaying the su:rr"orndÍng fierd fon the srrrfrowen beetre. The incídence of pa::asitism on JvIy 22 was 64.7 pencent. usÍng the data on the incidence of panasitism (Tabre 57) and the estimates of host density in the plot (TabLe 27, p.150), Figures 30 and 31 were prepared to depict the density of par.asitized. and non_ panasitized l-a'vae throughout the cor-rection peniod. rn Figure 30, the Tab1e 57. Pe::cent panasitÍs-r, of fir"st-, second-o third- and fou::th-instan of the sunflowen qxclamationþ, g;;;;;;p¡U*.r_arvae rnacei-ra *::t:: ?"r.ál?",m" or in a sampring proÏìffi-oããffi., t97s Sampling ::cent sta date TUt s2 T---E Jure 17 286 g5 0.0 0 June - 0 _ 0 _ 35 0.0 20 g2O 1S1 0.0 0 - 0 _ 0 _ 156 0.0 June 27 ¿rlq .lôô Ec E ;: å : ff3 _3:3 ê ; Julv 1 trÂa .nÈ cc ,ã 'ulo å : ;ffi i3:; JuJ-v 4 son t.t.l n a ;;:; ï roo.o i8i å3:3 ^o ^? '33:3 Julv I qÂtr .e4 âô ô ;; ff.; .i i??, ?3:3 *rI_v_z¿ _ _ Z3g _ _ _il+ _28.6 so 62 .o 713 61.1 Eeãn- E--sã.ã - rz+z- ¡i:á- -rËtË -;t'.i - -;r=b- ;;5- rg'åå -Bi.É lPanasitism detenrnined by dissection of l_anvae. "S::ä**ïï":iy'; , ;Eå - ,o"." thneshord temper.at*e , -"î î*;J:i:ã..Èjl;';'ä.an d us in g"aa irv ai statíon ; ;öå";i'J:";åä'äffi "ï;ffJa the 3LL:i:iÏT at Monris, Manitoúa.?]ll - r L.: ":o'':*';land Lu 1t -2'"3 finst- to fou::th-insta:r l_arvae of the host. (¡N) O) 257 Figur:e 30. Parasítism of lar"vae of the sunflower beetle, Zygogramma exclamationis, by Donyphonophaga macella at Ste. Jean, Manitoba, ín 1975. Shaded area = panasitized larvae, unshaded = non-parasitized larvae c o À r-- (g o U' É $ c € o- o v, õ- (v) 2 Ê o \o. (It U' s =+T=HSYKI=/' € c (\l Ê o /¿'\ o. ./ o U' \ tr U' 400 50 600 Accumulated Thermat Units (a.+"C T'LO ) June 258 Figur.e 31. Density of maggots of the pa::asite, Doryphorophaga macella, and lar"vae of the sunflowe:: beetle, Zygogramma exclamationis at Ste. Jean, Manitoba, in 1975 I tr6 g À à\5 o -ct E4 z 300 400 500 600 700 800 Accurnulated Thermal Units (a.¿"c T'Lo) 259 density of parasitized and non-parasitized l-ar"vae of each of the four instars is depicted whil-e the same information \^ras used for. Figur"e 31 to depíct the incidence of par.asitisrn of all for¡r instars combined. Á'l qn tho âonc.'+r¡ m=na I nf Tl ¡r¡quurrql . måøsotsLo r¡¡ìn theLrrç prunlOt L iSIð ShOWnòIIUWll inll,l FiSUre_ _Ò*^ , 31, the rater value being calculated fr"om data on the incidence of slrperparasitism in the plot (section 4.4.2.4)" A ToLO of g.4oc was selected for the calcul-ation of TU accumul-ations used for the X-axis ín Figures 30 and 31- because it was the ToLO used for per.vious developmental studies fo:: the rarval- stage of the host (Figure 16, p.152). A ToLO associated with the larval stage of the host is more applicable to use than a ToLO associated with the parasite becar:se the parasite (maggot) remains nelatively ínactive and does not kill the host until- after the host completes the fourth instar". Lanviposition by D. macella was well svnchronized with the host poPul-ation in the Ste. Jean plot. After parasitism was fir.st noted on June 24 (373 TUrs), larviposition kept pace with the increasing host popuJ-ation untir Jul-y 11 (586 TU's) when the peak numben of 1arvae and. maggots per plant was recorded at 6.54 and 8.63, respectivety (Fígure oL).?l I n-LLuuugrrar +hn,,-h +'uhere were more rnaggots than hosts per plant on July 11, only 4.76 (72.Beo) of the hosts were parasitized. Thenefore, onJ-y 4.76 of the 8.63 maggots per plant coul-d develop while the remainder" (9.87 o¡ 4l+.89o) were ineffective since onl¡r one parasite develops per host l-anva. 260 Lt.+.2.2 Letellier' , 7976 The mean incidence of parasitism by D. nacelra on first-, second-, third, and fou¡rth-instar' la:ivae in the Letellier" ptot fnom Jure 15 to August 6, 1976 was 3r.2, 41".7, 45.4 and 42.0 pencent, respectiveJ-y (Table 58). Parasitized larvae were first for-md on Jule 15, the same day the fir"st l_arvae v¡e:re found.. Figur"es 32 and 33 were prepar.ed using the data on the incidence of par:asitism (Tabl_e 58) and the estimates of larval density (Table 28, p.154) in the Letel-lier nânãqi+izo,1 plot. The density of *..=nÅ - non- parasitized first- to four.th-instan lar"vae is depicted in Figure i2 whil-e the incidence of parasitism of all four instars combined is shown in Figune 33. As was the case ín the 1975 plot at Ste. Jean, D. nncella appeared well s}mchronized wíth the larval population in the 1976 plot at Letel-l-ier. Panasitism by D. macerla kept pace with the l_arr.al popu- ration nith peak nur.iber of larvae and maggots being recorded at 3.6g and 2.34 per" p]ant, respectively, on Ju.ly 16 (nZ fU,s¡ (Figure 33). The incidence of parasitism on July 16 was 46. B percent with an averaqe of 1.72 parasitized .l-ar:vae per plant. Both the host and par.asite numbers wene thus substantialry less in the Letellier" nl or rh¡n those found in the St. Jean plot, in 1975 (Figunes 30 and 31). 4.4.2. 3 Lowe Far"m, 797i fn collections of first- to founth-instar lanvae at the p-l_ot at Lowe Far"m from Jurre 7 to JuJ-y 29 , 1,977, the mean incidence of panasitism Tab1e 58. Percent par"asitism' of fir"st-, second-, thir.d- and fourth -in starn lar"vae of the srnflowen beetle , Zygogranrna exclamationis, by Dorypho::ophaga nacella in a sampting proTãTïffitler;- Mã-fEõbã, 19 76 _ 9a¡pfe size (N) an<1 per"cent panasitièm (e,) olinstár"a sãfTfTrlttìù --."r---_Ò *r_-_-_N-____ãT-_-"_-r*___T_-jil-:-ã_L 1 L2 Ls Lq Lr-Lu uqLsJ-+^ rltl¿v ò^¿ Jure l-5 394 5 20.0 0-0 0 - 5 20.0 Jrne 18 41-0 3 0.0 s 40.0 0 0 - B 25.0 J:g:le 22 453 16 31.3 14 28.6 4 nn 0 - 34 26.5 .Irrie 25 490 44 25.0 6 83.3 3 0 - 53 30.2 June 29 529 75 33" 3 B 50.0 16 43.8 o JJ. Õ rv¿ .to. J JuJ-y 2 552 74 40.5 15 46.7 7 1_ 100 .0 97 40 .2 JuJ-y 6 607 40 40.0 I 3 44.6 24 lt 4 n s 60.0 tÞ2 43.4 July 9 648 39 35"9 40 45.0 49 44.9 10 30.0 138 41.3 Juty 13 695 18 22.2 26 38.5 73 43.9 70 48.6 t}l +2.8' July 16 722 5 60.0 58 34.5 88 ct. ó t29 48.1 280 46.8 JuIy 20 7720- 10 40.0 20 qq n 79 32.9 109 37.6 July 23 808 0 - 1 0.0 15 46.7 29 37 .9 45 40.0 ,Jr:Ly 27 8600- 0-2 ôô 1.4 27.4 16 18 . B JuJ-y 30 891 0 - ^áu-.L 100. 0 10 40.0 tt 45.5 3 Aug YJl-^ ^4 U - ^rìv- ^ ^^ UW. U q 961 0 v-u 25.0 å"g li¡7i - ^^ 4 25.0 4 Mean - {rIY -^;-;-ór. z - - -^F-- loo- +t.t- - soã 35'/ 4'2 .O !244 40 " I 1Pa:rasitism detenmined 2Thenmal by ciissection of l-arvae. units (TI-lts) caicul-ated using an B.4oC lower thr"eshold temperature, starting on April 1, 7976.. and using daily ain temperature data from the weather" station a-t Morr.is Manitoba. 3, . "L L L ancì L first- to fourth-instar" larvae 1234, , , of the host. N) ÞO) 262 Figure 32. Parasitism of larvae of the sunflowen beetle, Zygognanrna exclamationis, by Donyphonophaga nncel.Ia at Letellier:, Manitoba, in 1976. Shaded area = parasitized larvae, unshaded area = non-parasitized larvae o.75 tr o "a\ (¡ cØ *.t o.75 (! o- r.\ o ø tr Þ CÐ o.7 G o- (!-- o Ø E E c(\l o.75 c (It o-- gl (g (t) tr (t, o.75 400 600 700 800 900... Accumulated Thermal Units (g.dC T'LO) Jr"e t ¡"ly Æ lo \) Figure 33. Density of maggots of the parasite, Doryphorophaga macella' and lanvae of the sunflowen beetle, Zygogramma exclamationis, at Letelli e:r , Mani.toba, in 19 76 4 larvae (g l- .À2 /V """8 o Eot Ð -o z ru,f sitized ffi:: !arvae @ ".*a*'--*"'årffi.* @'a{@ ç_å a*@ ¡a@,r5åu"'-..d -*fu_ f ,""'sff @@ ,'-ås ! tþu 400 500 600 700 800 Accurnu lated Thermal Units (9.+'C 264 by D. macell-a was 11.3, 24.2r 35"3 and 39.2 percent, respectively (ra¡re 59). No parasitized lanvae wer.e taken in the pJ-ot r:ntil Jr¡le 14, one week aÊten the fír.st host rarvae were observed in the prot. The estimated density of the host (tabte 29, p.156) and the incidence of panasitism by D. rnacella (rabte 59) r^¡ere used to prepare jah Fi ollrcq vf?lr ur¡uen¿l îE r^rh uuvrvrlanr'nr- u +l-uo€ ^ c.ensf,l^^-i+,, ty or^ç parasitized^- and non- parasitized la¡vae of the sunfrower beetl-e in the Lowe Fa¡m plot, in The rar"val population peaked at 13.4 rarvae per plant (Figure 35) which was the highest value recorded in al-t ptots sampled fron 1975- 1977'- but the density of maggots of D. rracel-la peaked at only 3.93 pen plant which was substantiall5r l_ower than the 8.63 per plant recorded at Ste. Jean, in 1-975, (Figure 31) anC somewhat higher than the 2.34 maggpts per pÌant recorcecl at Leterlier, in 1976 (Figur"e 33). Even thouglt the inqidence of par.asitism was relatively low in the Lovre Farm pJ-ot, D. mggella. still appeared to be well s¡rnchnonized v¡ith the l_arval population since parasitism was noted shortly after finst hatch of the host and the increase in host density was matched fairty ctosely with an increase in the densíty of maggots of D. nacel_ra in the plot (Figure 4.4.2.4 (rrnorn:¡¡eìfic- Superparasitism was corÌinon in field coll-ections of larvae of the su¡tflowen beetle and it was aDDarent that the parasite has no mechanism to determine whether or not a host larva was parr:sitizeci. Table 59. Percent parasitisml of fir"st-, second-, thir"d- and fourth-instar larvae of the sunflower" beetle , Zygogramma excl-amatíonis, by Dor"l¡phorr¡phaga macell-a in a sampting pto , 1977 SamD I lnø Lr Lz L3 Lra LfL'+ date TUts2 I'l 9o N 90 N 9o N 90 N 90 June 7 453 1 0"0 0 - 0 - 1_ 0.0 June 10 469 15 0 .0 v- 0 - 0 - 15 0.0 Jr:ne 14 49 3 82 7.2 0- 0 - 0 - 82 t.2 June 17 s22 133 10.5 ^ ôô ô 0 - 0 - 136 11.0 Jrne 21 44 20. 5 0 - 0 - 360 14.4 Jr-ne 24 590 502 70 "2 231 20 .B 1J1 23 .7 0 - 746 73.l Jrrre 28 638 q69 7.2 383 24.3 L75 32.6 0 - 7027 17.9 JuJ-y 1 659 377 1.0 336 20.3 287 35.6 13 69.2 1007 20.4 July 5 1to 119 26.9 263 20.2 413 38.0 r42 41.6 937 32 .t July B 747 109 29.3 154 27.3 316 34 . 5 ztt 40 .5 796 34. 1 Ju.l-y 12 790 35 25 "7 118 40.6 231 27.8 382 35.6 772 33.6 July 15 827 1_7 9.1 68 30.9 154 29.6 257 29.3 5 30 29.3 July 19 881 1_ 0.0 7 42.9 80 47.2 15 5 4I .4 243 45 "7 J,aIy 22 913 0 - 6 66.7 42 42.9 7! 53.5 119 50.4 JuJ-y 26 9570- 0- 7 42 .9 57 52 .6 64 51.6 ¿uf_V_Zg 0- 0 77 41.7 77 47.7 _ 9880------^-h1-¿ )-oL+ -,7 _t . J - - Mean -L _LO_tJ ¿+.¿ r7z[ s5.ã - TsSr- ãs]- lesT zslo- lPanasitisn deter"mined by dissection of larvae. zThermal r.riits (TUts) caf culated using an 8.4oC lower threshold +êmñêrâ fr1Þê stanting on Apr"il 1, 1977, and using daily air temperature data from the weather. station at l'{o::nis, Manitoba. ?- 'L , L , L , and L first- to fourth-instar" la¡.vae of the host. t\) 266 Figune 34. Parasitism of larvae of the sunflower beetle, Zygogramma exclamatiorris, by Dor"yphorophaga macella at Lowe Farm, Manitoba, ín 1,977. Shaded alrea = parasitized la::vae, urishaded - non-parasitized larvae s \À ",å#-åm*.*.+ o Ø ;**t o \o- $ U' Ê E CO g \CI- u- (E v) C 1t c ô¡ o à \ ¡'ì o ø tr Ø 3 400 sooroo 600 700 800 900 Accumulated Thermal Units (84"C T.LO) June 267 Figure 35. Density of maggots of the par"asíte, Donyphor.ophaga nncella, and Ìarvae of the surrflower beetle, Zygognamma exclarnationis, at Lowe Farm, I'fanitoba, ín 1977 14 12 10 c o dcL\ @ o -o # E f z. å & @ Ê &@e & r*"' &. ."-P" @ & ok -.**e*î 400 soo 600 700 800 900. 1000 Accumulated Thermal units (e.q'c T'LO) 268 For" example, in 7975, at ste. Jeano 40 to 50 percent of the panasitized l-anvae corrected containecl two or more maggots, and since only one parasite develops per host larva, the supernuûìerary maggots were Íneffective (Table 60, Figure 36)" In j.976, at Letel-l-ier, 25 to 30 per"cent of the parasitized lanvae contained two o¡ more maggots while, in 1977, at Lowe Farm, 10 to 20 per-cent of the parasitízed lanvae con- tained two olr rìol:e maggots. The high incidence of superparasitism in nl a+a T the nl of at Rte ,To¡n--*^- nnmnr¡o,l--...rsres fev ^ l,rvLù oL-+ !s.=rlier^+^ì and Lov¡e Farm was due to the high incidence of parasitism in the fonner. Since D. macella is r¡nable to distinguish between parasitized anrl non-parasitized hosts, and only one Parasite can develop per lar"va, D. rnacell-a v¡oul-d rnake most efficient use of the maggots produced in fiel-ds of high host density and/on l-ow inciCence of parasitism. 4.4.2.5 Relative incidence of parasitisrn among instars An estiinate of the relative incidence of parasitism among instars was made by comparing the niean number" of nraggots in larvae in each of the four instars. Since the parasite does not kill the host until- afrten the l-arval stage is completed (Section 4.4.1.3.2) and all_ l-anval instars ar€ susceptible to attack (Section 4.4.1_.2.3), íncidence of parasitism and superparasitism woul-d be expected to be cumul-ative through the lqr"val per"iod. rn 1975" at ste. Jean, the mean numbe¡ of maggots per first-, second-, thir"d- , and four"th-instar lar"va was 0 . 81 , L.2s , 1. 33 and !.22 , respectively (Table 60). The incr.ease betrveen the fírst and second Tabl-e 60. Distnibution of maggots of the pa:rasite, Doryphonophaga macella, among the different ínstars of the sunfl-or^ier beãEÏ{-Z}Sþãäma exclarnationis, from field plots at Ste. Jean in 1975, LetellieFG fgZO, ãã Lowe Farm ín 1-977 St of l-arvae with 0-4 massot(çfg s Maggots/ instar m5---T-1 Ma ts /larva2 rasitized lanva Ste. Jean 197s Lt 16 9B 47 .2 lno iU.U I.J ôq 0. B1a I Ãlr ôf! 1 n T,^ !z+ z 27.4 ¿+.r ^J.t ?n T.^ 1009 ¿+.'J 22.7 9 .2 l_r R r. /o Lq ol^ 28.2 lta K 4'l a a a 3.1 7.22 b 7.71. Letellien l-Y /o Lr ù J-Y 65 .8 îtr lr 7.8 0.9 0 0.44a 4 aa T.- ?na loD 9.8 0.4 na 0 .55ab .1 . JI T. ^ 54 .6 It a 10.6 1_.3 0.7 0.61 b I Q'l La 58 .0 ?aì ? qt2^ 0.6 0 .57ab Lowe Farm LJII 4 lt 4 aì I â- Lr 2164 BB.B r.l ^V.A 0 1 12 tt a fì tr Lz -L O.L J 75. B 0.1 0.30 b 1 a^ 4'7 Olt q?n r, ^ 64 .7 0.43 c 1/)1 1l at L4 -LJ:lt- 60.8 7 .0 1-.0 0.2 0.49 c lIncludes larvae with four or more maggots 2l'learrs fnorn the same plot foli-owed by ihe same letter were nct --Ò..--ql on I1t ntnt l1¡ different (P=0.05) according to the LSD test. The data wene rarrmã l r'zod |rr¡ ¡ f/Îi:f trar:sforrntion príor to analysis. f.J 270 Figur:e 36. Incidence of par.asi'tism and superpalrasítism of Zygog::amma exclamationís by Doryphorophaga mace]la in plots at Ste. Jean in 7975,. Letel-lier in 1976 and Lowe Fanm, in 1977 ^ l'1 = number of maggots of D. macella per" host l_a::va. Ste. Jean -1975 l-etellier-1976 Lowe Farm -1977 oo) o È Host Instar Host Instar Host lnstar 277 instar was significant suggesting that parasites wene larvipositing in second- as r¡ell- as first-instar larvae. There vras no siqnificanr difference between the incidence recorcied amons larvae in instars two to four. A visual assessment of Figure 30 , p.257 supports the fÍnding that the nrajority of the larviposition took place in tlie first two larval instars with a l-esser amount in third-. and fourth-instar la::vae" The mean number of maggots per first- to founth-instar lanva, in 1976, at Letellier r^¡as 0.44, 0.55, 0.61 and 0.57, respectively (Tabl-e 60). The only significant differ"ence in the incidence of panasitism was between the first and third instarn¡hich suggests that in this plot, nost of the larviposition occurred when the population was in the first instar with lesser nurnbers of maggots deposited in second-, and third-instar lanvae. A visual assessnent of Figure 32, p.262 deoictins the incidence of oarasitism of each of the four l-arvaf instars supports the above statement. In 1977, at Lowe Far"m, there was a rnean of 0.13, 0.39, 0.43 and 0.49 nnggots per first-, second-, thirC- and fourth-j-nstar, respectively (Table 60). The increase between the fir.st and second instar an Farm. A visuaf assessment of the Figur.e 34 supports the above finding that the incidence of parasitisrn increased through the first three instars. 272 Data from the sampling pì-ots thus indicated that most of the maggots of D. macel-la wer"e deposited in the fir.st two l-anval instars with fewer maggots being deposited in the last two ir:stars. However, in the l-aboratory all four instars were susceptible to attack and lqhen al-l instars wene present, D. macella deposited the majority of the maggots in third-, and founth-instan larvae (Section 4.4.7.2.3). One possible explanation fon the field nesul-ts is that most of the lanviposition period of D. ¡nacel-la may have been over" befone the.l-arval population of the host advanced to the third and fourth instan, thus, 'l it mav not hr. thât D - maee-l a nr"cfer.s fo lenvi nosit in f i'r.sìt- - and second-instan l-arvae, but that these instar.s ane most prevalent during the majonity of the l-ar"viposition period. l(el-leher (1960) stated that jn D- rìor"vnhor"¡e lar"vioositefl thír-d-., enrìs¡¡v forr¡th-instaf larVae of the jt jS Oolon:Án n^t:t^ hee't-lc-L+v) h¡tr not Clear v¡hethef he eXamirred fir'st-- t or second-instar larvae for" incidence of parasitism" 4.4.2.6 Synchr.ony of D. macella r+ith the sunfl-ower beetle Data fr"om labonator"y r.ear-ing and field sarnpling wer.e used to detenmine holv wel-l- development of D. macella was synchr.onized with that of the sunflower" beetl-e in Manitoba. Parameters considened included the initiation of larviposition, nesponse to various host densities and 1 -'c^ timi¡s of emer"senee-..--- Ò-¡ruu of new-øenerationóe¡¡u!oLlvll adults.oUUILù. Thesel-.--- r----noints in tL^-lre IIIti cycJ-e of the parasite wene chosen because they coulC be readily determined in the sampling plots studied. 213 4.4.2.6.1 Initiation of lar"viposition , 7975 to !977 To determine the initiatiori of larviposition b]' the over- wintenirrg population of the par"asite, data on parasitism, obtained from previous dissectíons of host larvae col-l-ected at twice weekly inter"vals f,nom five fiefds- was exaniined. The finst parasitized l-arvae wer"e found in each plot within one week of first hatch of host eggs (ta¡te 0t). Lanvipositing females must have been present in the field by June 24 in 7975, June B in 1976 qt:u=¡â r'¡qJM=r¡ ur1l rlti¡ lJl oe? I t t nL^I ltc òPt rrIB timed with the start of hatching of its host. Unfortunately it was not knovm wher"e these sp::ing adults were coming from or why they were in good synch:rony with the host since the over-win'[ering stage on locatiorr of the parasite was not dete::mined (Section 4.4.2.7). Kellehen (1966) noted that in Manitoba, D" doryphor"ae maggots wene first r"ecovered fr"om l-arvae of the Colonado potato beetl-e ar.ound July 15. 4.+.2.6.2 Response to host density, 1973 to Ig77 An assessment of the abitity of D. macella to respond to various host densities was obtained by determining the incidence of parasitism in seven sunflower" fields duning the per:iod 1973 to 1,977. Incidence of nar.¡sítísm fon thnee,nree ofor theseInese fieldsrJ-eJ_cs hasnas beenDeen reDontedI€r_- previousf_,__*"*y (Sections 4.4.2.1 to 4.4.2.3). The additional fou¡ fietds were located at Monden and Car"men, in 1973, Rosebank, in L974, and Ste. Jean, in 1977. The incidence of parasitism at peak host density was used for qJ.rrâr¡ flro nrr¡nncac ¡€ +hr'c usuJ . 274 T-L1^ âl Date on rvhich par"asitísm by Doryphorophaga macel-la was first noted on IãGã-õT-the- ãunFI-orve r b ee tL e, Zygo gramma exclama t ioni s, during the spning of 1975, 1-976, anò 7977 Sampling First host Fir.sf nãr'âsìtízeçl Yean location Ia:rva host l-anva 1975 Ste. Jean June 17 June 2l-l 7976 Rosenfeld June 4 June B 7976 Letellier June 15 June 15 1977 Ste. Jean May 31 May 31 7977 Lowe Fa¡m June 7 June 14 275 Lanval densities in the seven fields ranged fr.om 3 .7 to 29.4 pen plant and parasitism ranged from 1.5 to 72.8 percent (Tabte 62). when panasitism was plotted agaÍnst larval density for" each plot, a negative sloping regression rine was obtained which had a non-significant cornelation coefficient of 0.52 (Figure 37). (Larval density was subjected to a log tnansforrnation and percent parasitism to an ansular" trarrsformation). D. macel-la appeared to act in an inver"se density- dependent manner on the sunfl-ov¡er beetle, that is, as lanval- density incr"eased, the relative impact of D. macella decr"eased. D. macella, thus, was present ill more or less ecuat densities fnom year to year arrd fiel-d to field and it fait-ed to nespond to high host densities by increasíng the incidence of parasitism. Reasons for" this lack of ñ^-r- nêqn^nqê 2nê knOl¡n. AdditionalLrv¡¡q¿ fieldsr rçrUò withWI Lll Au ranse! u¡¿óu ofvr hostttvù L densities would have to be sampled to further" test the density rel-ationship between host and panasite. Harcourt (rg7r) found that D. donyphor"ae acted in an inverse density-dependent mannen when panasitizing the Colorado potato beetle on potato, wheneas Latheef and Har"court (1974) for¡nd that D. doryphor.ae acted in a density-dependerrt manner f-on the same host feeding on tomato. 4.4.2.6.3 synchrony of new-genenation parasites with host Larvae rn the field, emergence of new-generation adults of D. macella was in poon synchr"ony with the larva.l- population of the sunflor¡er beetle. New-generation parasites emerge at about the same time as new-genenation adul-ts of the host (section 4.4.1 .5.2), about the time 276 Table 62. fncidence of parasitism of lanvae of the sunflower beette, Zygogramrna exclamationis, by Doryphorophaga macella in seven sunflowe:r fields in south-central Manitoba. 7gl3-1977 Loeation Sampling date % r:ara ci f i zorì Larvae,/pIant Morden July 11, 1973 279 20.8 tq L! Car"man July 17, 1973 2s9 Rosebank July 24, 1974 240 q, al Ste. Jean July 11, 1975 647 104 Letell-ier July 16 " 7976 280 46 .8 Q+o .To= n June 21, 7977 I Zö 30 .6 '74 Lowe Farm June 28, 7979 1027 17 q 277 Figure 37. Relatíonship between density of larvae of the sr:r¡flower^ beetle, Zygogr"amma exclamationis, and po:cent parasitization by D.oryphoroPhaga macella Ê 12 = o.s2 .9 o .! q, o o o. c o o o o. c G o E Mean LarvaeTplant 278 most of the 1anva] population has completed development (Table 2g, p¡154 to Table 30, p.15g, Section 4.1.6.6). l,lew_genenation panasites must, thus, eithen r-eave the field in seanch of othen on ar_tennate hosts or penÍsh without nepnoducing. Ìt wourd, ther.efore, seem unlikely that D. macella pnoduces mone than one gehenation pe,. yean on the su¡flowen beetle, and that new-genenation par-asites ane in poor synchr"ony with the sunflower" beetle. (fgOO) Kellehen noted a simil_an l_ack of sJmchnony for new-generation adults of D. doryphonae on the color"ado potato beetre. 4.4.2.7 Ovenwinter"ing The ovenwinte::Íng stage and locatíon f,on D. nracella was not detenmined in this study, but the panasite díd not ovenwinten in assocíation with the sunflower" beetre. rn the laborator:y, no sign of pupaL diapause was obsenved, non was thene any evidence that D. macel-J_a ovenwintened as a maggot in ovenwintening beetres. Maggots of D. macerra obsenved in adurts of the host wene dead and encapsurated. As note.d, new-generâation adults of D. macelra must leave the fÍe]d in which they develop in or:den to find a suitable host (Section 4.4.2.6). ft may be possible that a second genenationo pnoduced on an unknown alternate hosto fo'rns the ovenwíntening population. Anothen possibility is that D. rnacella does not ove::wínten in Manitoba and is blown in fr.om the south each spníng. 4 .4 .2.8 Hypenpar:asites Per"írampus (Hymenopte¡a:penÍr-ampidae) sp. was neaned fnom D. macella pupania or"iginating fuom founth-ínstar. lanvae of the sunflowen 279 beetl-e corrected in the fierd. Howeve::, the íncidence of panasitism was l_ow. In 1916, one perilampus sp. and 44g adults of D. macell_a emenged fnom a total 0f 520 pupania of D. macer-ra, wheneas ín 1g77, two Pe'irampus sp. and 714 adur-ts of D. macerla emer^ged fuom a totar of 825 pupania. The ::emainÍng panasite pupae died, pnesu'abry fnom poor physieal condition. 280 5. SUMMARY AND CONCLUSIONS Most of the data pnesented in this thesÍs deals wíth basic biological info'lrntion concerning the rífe histony of the sunfl_owen beetle and its panasites. Genenal]-y, the data pnesented on the rife histony of the beetLe agllee with eanlien wonk in Manitoba by criddle (tszz), westdal and'Bannet (rgss), and lrestdal (rgzs), and with wonk in Texas by Rogens (7977). The data on Myiopharus sp. is difficult to compa:r'e with othen wonks since the only othen infonmation avai.l-able is on a dÍffenent species in same the genus (Daviault 1941), but a numben of basic simÍlanities have been noted,. Erixestus l¡rnnemana_ Ís anothen, nelatively unknown panasite, nefenences on the life histony of this pteroraJ-Íd ane scance and bnief. Donyphorophaga macel_la has been studied in Manitoba (1960, by Kellehen 1966) as a panasite of the colonado potato beetre. Howeven, much of his wor.k d.ealt sríth D. donyphonae sÍnce he consídened D. macer_la to be of minon impontance nelative to D. donyphor-ae. The data pnesented in this disser.tation wi1l, thenefo'e, signifÍcantl-y bnoaden the base of infonmation available on these panasites. The sunfrowen beetle is univor-tine and over.winters as a sex'ally immatr::re adult Ín the soil, us'ally at a depth of 15 cm or less, in fields ín whÍch it completed. lar:val devel0pment. Removar_ of snolr cover mid in winten was assocíated with íncneased ovenwíntening mortalÍty. since sunfrowen tnash coven is often used to tnap snov¡ to íncnease soil rnoisture, a recommendation to decnease the snow coven to incnease beetle mortality woutd be in conflict wíth necommended agnonomÍc pnactice. ' 28]- A system was pnoposed for predicting fírst eme'gence of oven_ wintened beetles in south-centrar Manitoba. using this system, emengence woul-d be expected aften an accumuration of 235 TU's (ooc rolo) based on soir- tempenatune necor.dÍngs fuom a depth of 5 cm. Thís system may be used to arer.t growers as to when to expect posthibennation beetles in sr¡rrflowen fields. Posthíbennation sexual devel0prnent was napid, mating being noted within two days of emengence a'd egg-laying within one week of emengence. Once oviposÍtion $ras Ínitiatedr eggs wene r-aid. almost eveny day du:ring the oviposition peniod. rn the field, females laid an avenage of 15 2 eggs pen day ' over a mean ovipositíon peniod of 47 .t days fon a total egg ptoduction of 71g. rn the r_abonatony, howeven, each female laid an avenage g0.7 of eggs pen day oven 60.7 days for. a total pr"oductíon of 11965 eggs. Egg pnoduction in the labonatory was ther"efone mo::e than doubre that in the fÍeld. The high neaning temper"at*e (zsoc) in the labonatony and pr.otected conditions may pantially explain this dÍffenence. The extended oviposition peniod nesulted Ín an extended hatching peniod which made the selection of an optimum time for^ Ianval control_ mone complicated. The estimated ToLo and TU nequinements fo:: each of the lÍfe stages was detenmíned by means of constant tempenature tniars in the laborator:y' These esti¡nates may find use as base-line infonnation fon a computen nodel- to pnedict development of the beetle in south-centnal Manitoba. 282 The mid-point Ín the deveropment of the second.-Ínstan was pnoposed as the optimar time fon contnol of la::vae since at that time most eggs have hatched and líttle foliage danrage has occu:nned. This point in lanva1 development occunned 2I days on 204 TU,s (g.4o ToLO) aften finst hatch was noted. rt was reconmend.ed. that gnowens eheck thein sunflowen fier.ds every three on fou:r days duning eanry deveJ-op_ ment to determine the stant of hatching, so that necommend.ed. insecticides coul-d be applied at the appnopniate time if the pest density exceeds the thr'eshord value. cr:::::entry, the pnovincial r:ecommendations ane that insecticides be appried for ranval contnor- aften a1r eggs have hatched (llestdal et al- !976) but befor.e the pl_ants neach a height of 60 (Anonymous cm 1g7g c) ir thene ane 10 on more ranvae pen plant (Anonymous r'21 1g7g a). The days fnom finst hatch, necommendation should, thenefone, furthen aid the gnower in deciding when to spnay and thus make mone effective use of the Ínsecticides that ane appried. Addítional tnials should be conducted using the new necommendation to deter"mine whethen the thneshold value of 10 ranvae pen plant is stil_l applicable. An inventory of pnedators and par:asites of the sunfrower. beetle, in Manitoba, was cond.ucted dur"ing the course of the study, and is the finst extensive work on natunal contnol agents of the beetLe. Nine specíes pnedatons of wene neponted, six of which ane new neconds fon the sr:nfrowen beetr-e. Fou:: species of panasites wene nea¡:ed fnom thnee diffenent rife stages, alJ- species being new r€cor?ds for. the sunfl0wer" beetle and one, Myiophanus sp., being a new species. The 283 bionomics of the panasites wene studied to d.etermíne thein impact on the beetre and thein usefulness to the g'ov¡en, and to d.etenmine how insecticide applieations might affect the panasite complex. Myíophanus sp. ís a panasite of adults of the sunflower beetle. The panasite overwÍnter"s as a maggot in the overwintening host, and kills it in the spning befone it emenges. The panasite emenges about one month afte:: the non-panasitized host, but within a shont time begirrs to deposit maggots in the rast of the posthibennation popuration. Panasites that áevelop in these posthiber.natÍon beetles emenge in late sumrner' ín time to ranvíposit Ín pnehibennation beetles. The maggots deposited by second-genenation adults fonm the over.wintering popul-ation. Myiophanus sp. thus has two genenations per yean whíle its host, the sunflowen beetle, has only one gener:ation. The ovenwintenÍng popuratio'of Myiophanus sp. is impontant because panasítized beetles ane killed pr"íon to emengence Ín the spr.ing. This montality resurts in a ::eduction in numbens of posthiber.nation beetl-es and poter:tial offsp::ing, and subsequentJ_y a neductíon in damage to prants The ' value of the second. oï1 summer genenatíon of Myiophanus sp' is pnobably less appanent than that of the ovenwintening genenatior¡ because the posthibennation beetles kilred by this genenatíon wour-d. have been nean the end of their lífe span when they wene kírred and thus would have been abre to do considerable damage befone they died. rn the long nun, howeven, the summen gene::ation is Ímportant because the adults of this genenation arle the pr.ogenitons of the ovenwintening popuration of panasites which develops from panasitism of pr"ehibennation beetles. 284 since.the finst adults of MyÍophar.us sp. emerge approximately one month laten than overwintened beetres, insecticides applied fon control of posthibennation beet.l-es, during this o¡:e month peniod, shourd r¡ot affect the panasite because it would still be in the soil of sunflowen fíelds of the pnevious year. consideníng that the avenage date of finst emergence of the sunfrower beetl-e, d.u::ing this study, was May 20, insecticides applied before mid-June shoul-d not affect Myiophanus sp. in most yeans. The TU accumuratíon system pr:oposed fon pnedícting finst . emengence of posthibennation beetr-es may arso find use in identifying a safe spray peniod fon Myiophar.us sp. Enixestus wínnemana is a parasite of eggs of the sunfrower. beetle. This panasite ís pa::ticulanly effective because it eliminates the pest ín the egg stage. fts effectiveness is enhaneed by the fact that it develops napidry and can pnoduce mone than one genenation pen yean' steps taken to incnease the sunvíval of this parasíte may nesurt in high egg montality, row larvar numbens and neduced prant damage. rnsecticides applied fon contnol of posthibennation beetl-es p::obably would have an advense affect on E. winnemana. panasite adults would be pnesent in sunflowen fields dr::ring eanry June when sp'ays Íìay be applied for beetre control. Fierd tnials ane nequined to detenmine the effects of insecticides on subsequent egg deposition by post_ hibennation beetl-es and. on panasítísm by E. winnemana. rnsecticÍdes appried fon contnor of lanvae of the sunfrowen beetle pnobabry wour-d have ress ímpact on E. winnernana because they woul-d be applied when thene wour-d be few eggs nenaining on plants. 285 Again, field tnials ane r:equined to determine the effects of insecticides on populations of E. wÍnnemana in the shont tenm and fnom year to yean. Do::ypho¡ophaga macella J-anviposits irr eanÌy-instan 1ar.vae of the srmflowe:r beetle, but panasitízed lanvae are not killed u¡rtil the pnepupal stage. Therefone, D. macella is of l-imited va]ue in the shont tenm because lanvae Parasitized contir¡ue to defoliate sunflor4rers as d.o the non-panasitized lanvae. rn fields whene lanva] abund.ance exceed.s the economic thneshold value, insectÍcides may have to be applied fon contr:ol of the lanvae even if a substantiar pontion of the popul_ation may be panasitized. Ther"e aPpeans to be no pnactical way to contnol lanvae of the sunflower beetle with insectícides wÍthout destnoyirrg D. macerla since the parasite pnesent Ís in the field and lanviposÍting within a week of the appeanance of host l-anvae and thnoughout the peniod that is rrost advantageous fon contnol of the host. Tt is difficult to pr.edict what effect a r-anvar spray pnogram may have on the incidence of panasitism fnom year to yean because the ovenwinte'ing stage and. location of D. uncerla is not known. rt may ovenwinten in some unknown aLtennate host on it may blow in fnom the south each spning. 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Senv. 421,37pp. 302 Appendix 1. stages of ooc]rte deveropment in the sunflowen beetreo Zygog:ramm exclamationis (Genben et al 1g7g). Pnevitellogerresis stage r - Oocytes ane not distinguishable iri whole mounts the ovanies, of but one on two small_ oocytes can be seen in hístological sections of some ovarioles. Stage Ir Oocytes - are distinguishable Ín whole mounts of the ovar:ies; and the ur-timate oocytes are < 0.4 mm Ìong. Vitellogenesis stage r - !":rv vÍterJ-ogenesís phase. ur-tinate oocyte is 0.4 - 0.8 mm long. Stage rr - Midvitelrogenesís phase. ur-timate oocyte ís 0.8 _ 1.2 mm long. stage rrr - Late vitelrogenesis phase. ur_timate oocyte is 7.2 - 1.6 mm long and d.oes not have a chonion. stage rv - urtimate oocyte is 1.3 - 1.7 mm long and has chonion. a