Diet Effects on Survivorship and Developmental Parameters Oftufted Apple Bud Moth, Platynota Idaeusalis (Walker) (Lepidoptera: Tortricidae)

Rev. Fac. Agron. (LUZ). 1997,14: 207-223

Diet effects on survivorship and developmental parameters oftufted apple bud moth, Platynota idaeusalis (Walker) (Lepidoptera: Tortricidae).

Efectos de la dieta en la supervivencia y parámetros de desarrollo de la polilla de la manzana Platynota idaeusalis (Walker) (Lepidoptera: Tortricidae).

Osear E. Dominguez-GiI1 Bruce A McPheron2 Abstract

Survivaloflarv ae, developmen k'll time, pupal and adultweights of the tufted apple moth Platynota idaeusalis (Walker) (Lepidoptera: Tortricidae), were moni tored in the laboratory for a comparison of performance among a lima bean-based synthetic diet and four different host plant species: apple, Malus domestica (Bork.) ev. Red Yorking; black raspberry, Rubusoccidentalis L.; broad-Ieavedplantain, Plulttago major L.; and dandelion, Taraxacum officinale Wiggers. Artificial diet proved to be the best dietfor P. idaeusalis in survivorship and in all the develop mental parameters studied. Excluding artificial diet, survivorship was highest when feeding on apple, and lowest on dandelion at pupation, and at adult eclo sion. Black raspberry and plantain were intermediate in their effects. Develop mental time on apple was about the same as dandelion-fed larvae, whereas lar vae feeding on plantain had the longest developmental time taken to pupation and adult eclosion among all diets. Female larvae reared on black raspberry emerged 2.6 days later than males. compared with 0.3 days for apple-reared P. idaeusalis. Larvae reared on plantain produced the heaviest pupae and adult female among host plant species. followed by apple. dandelion, and black rasp berry. Key words: development. interaction (liet-insect, Platynota idaeusalis. apple. Resumen

Supervivencia de las larvas, tiempo de desarrollo, pesos de la pupas y adultos de la polilla de la manzana fueron comparados en tre una dieta artificial y cuatro diferentes especies de plantas hospederas: manzana, Malus domestica (Bork.)

Recibido el 09-11-1994. Aceptado el 14-10-1996 1. Departamento Fitosnnitario. Facultad de Agl'Onomín La Universidad del Zulia. Apartado 15378. Maracaibo, Venezuela. 2. Department of Entomology. Pennsylvania State University, University Park, USA

207 Domínguez-Gíl y McPheron

cv. Red Yorking; mora, Rubus occidentalis L.; llantén, Plantago major L.; y diente de león, Taraxacum officinale Wiggers. La dieta artificial fue la mejor para P. idaeusalis en todos los parámetros de desarrollo estudiados, pero hubo también un efecto significativo de las plantas hospederas. Supervivencia hasta pupación y eclosión del adulto fue mayor en laNas que se alimenL:"1ron de manzana yen cambio más baja en diente de león. Tiempo de desarrollo fue mas corto en larvas que se alimentaron en manzana y diente de león, mientras las larvas que se alimentaron de llantén tuvieron el tiempo de desarrollo más largo hasta pupación y eclosión de adultos. La eclosión de las hembras fue siempre posterior que la de los machos, pero la magnitud de la diferencia varió de acuerdo al hospedero. Las larvas criadas en llantén produjeron las pupas y adultos hembras más pesadas, en cambio mora produjolas más livianas. Palabras claves: desarrollo, interacción dieta-insecto, Platynota idaeusalis, manzana. Introduction

The tufted apple bud moth, noted that knowledge of P. idaeusalk'i Platynota idaeusalis (Walker) (Lepi biology on hosts other than apple, e. doptera: Tortricidae) is a native g., on ground cover within orchards. polyphagous herbivore thatis the most would be extremely useful in consid significant direct insect pestfor many ering the allocation of control mea apple growers in Pennsylvania (16, 19) sures. andother apple-producing areas along Though often found on other the Atlantic seaboard (18). crops, such as peach, pear, and sweet P. idaeusalis is a highly polypha and sour cherry, P. idaeusalis is not gous species [attacking at least 17 considered an important pesL other plant families (20)], there is a high than on apple (19, 28). However, popu probability for this insect to feed on a lations of P. idaeusalis that feed on wide range ofplants with unique secon these alternate hosts can be a source dary compounds. Second generation of reinfestation into apples. larvae overwinter as second through Although P. idaeusalis can feed fourth instars in larval shelters such on many different host plant species as rolled leaves and decaying fruit in (20), there is currently titUe knowledge apple, peach, cherry, andpearorchards on feeding preference. In a neonate and (8, 24) and complete development in fourth instar multi-choice assay, the spring on a variety ofherbaceous Dominguez-Gil et al. (11) found that species and apple root suckers (8). the number of neonates moving to Knight and Hull (19) found that adult apple and black raspberry leaf disks andlarval populations were often on a was higher than on dandelion andplan wide variety ofherbaceous plant spe tain. Plantain leafdisks were signifi cíes beneath host apple, pear, peach, cantly less preferred by neonates than nectarine, andcherry trees. They also those of apple, black raspberry, and

208 Rev. Fac. Agron. (LUZ). 1997.14: 207-223

dandelion. However, significantly more cies, condition, and quantity ofavail leaftissue was eonsumed by fourth in able food plants may be of great sig star larvae from apple and dandelion nifícance in determining insect popu than from black raspberry and plan lation levels (31). Potential host plants tain. They concluded that apple is a differ in their fluitability, their effectfl preferred host for both newly-hatched on larval development rate, pupal and older larvae, while young larvae weight. female fecundity, survivor preferred black raspberry over dande ship, and behavior (2. 4) and in their lion andplantain andolder larvae pre acceptance by larvae in laboratory fer. dandelion equally to apple, but choice tests and in the field. The choice more than either black raspberry or of foad plant and the composition of plantain. plant species may interact with vari Simelane (28), working with a ous environmental factors to influence field strain ofP. idaeusalis reared on the population biology of P. idaeusalis. apple, peach and cherry leaves, and The interaction ofthis pest with synthetic diet, found that host has an most ol' its non-crop host plants has influence on the survivorship and de not been thoroughly studied, but af velopmental time to adulthood. Larvae fects many components ofpest man reared on apple and cherry were not agement. Because of these plant spe significantly different in time to pupa cies are common weeds and contrib tion or adult eclosion or in pupal ute to P. idaeusalis population in the weights. P. idaeusalis larvae fed on orchard, it is important to understand peach developed faster and reached the influence ofplant allelochemical on higher pupal weight, whereas larvae the P. idaeusalis survival and devel feeding cherry took longer to develop opment, pesticide resistance. and andachieved the lowest pupal weights. detoxification ability. Little is known Survivorship was highest when feed about the effect these plants may have ing on apple and lowest on peach. He on the development and reproductive concluded that the type ofhost has an performance ofP. idaeusalis. influence on the developmental time, This study was designed to ex fitness, and mortality of P. idaeusalis. amine the larval performance of P . .Developmental rates may be different idaeusalis on four different host plant in cherry and peach orchards so that species: apple, MaJ.us domestica (Bork.) population dynamic predictions and cv. Red Yorking; black raspberry. Ru possibly timing of eontrol actions would bus occidentalis L.; broad-Ieaved plan have to be shifted to account for these tain, Plantago major L.; dandelion, differences (28). Taraxacum officinale Wiggers; plus a Thehostplant has long been rec lima bean-based synthethic diet. Per ognized as an important factor affect formance was measured as larval sur ing the population dynamics of phy vival to pupation and adult eclosion, tophagous insects (23). Although few development times, pupal weight, and studies of P. idaeusalis have focused adult body mass. on the role ofthe host plant, the spe

209 Domínguez-Gil y McPheron

Materials and methods

Host-plants. Host-plan t species strain was to select a strain resistant (table 1) were raised in a greenhouse specifically to azinphosmethyl. Prog at the Pennsylvania State University, eny from this collection were crossed University Park. Apple is the economi with a laboratory susceptible line, and cally important host ofP. idaeusalis; backcrossing to the lab susceptible line the other three species are present in wascarriedoutforfouradditionalgen the apple orchard and surroundingveg erations. At each backcross the por etation. The apple trees were cultivar tion of the genome that was suscep Red Yorking on Emla 7 root stock. tible increased by 50 %, so that after Black raspberries were started from four generations P. idaeusalis had ge cuttings. The remaining host species nomes approximately 94 % that ofthe were reared from seed in pottingsoil. susceptible strain. Repeated backeross All plants were transplanted to pots ing essentially creates an "isogenie" filled with Terra Lite Metro-Mix 25()íY strain by gradually diluting the frac Growing medium (E. C. Geiger, tion of the genome coming from the Harleysville, PA). Plants were fertil resistan parent (26). This method is ized every two months with water used to move a major resistance gene soluble 15-30-15 (N-P-K) fertilizer (4.0 into a susceptible genetic background gIL). Plants were watered as needed and thereby isolate itfrom other genes and grown under a 16-h photophase that affect the resistant phenotype. and ambient relative humidity. White The azinphosmethyl-resistant strain fly, thrips, mite and aphid infestations was selected with azinphosmethylin in the greenhouse necessitated the use three generations (F4 ,F7, FlO). of 2.5 % Safer insecticidal soap (50.5 Homozygosity of the resistant % potassium salts of fatty acids, Agro strain was increased by selection of Chem, Jamul, CA). As a precaution, larvae. Beginning with the first labo all host species were treated at the ratory generation, the strain was ex same time. posed to selection pressure through Test plants were selected arbi four generations by exposing neonates trarily from a group of individual to 25 ppm azinphosmethyl diet meor plants that were similar in height and poratíon assay. Selection was made phenology. For comparison with pre with neonates using 25 ppm azinphos vious studies, P. idaeusalis larvae methyl diet incorporation assay. This were aIro reared on a lima bean-based dose represents the LC99for the sus artificial diet (21). ceptible colony (6). The selection pro Insects. The genotype resistant tocol followed Biddinger (6). Formu· to azinphosmethyl used in this experi lated azinphosmethyl was applied (0.5 ment is a near isogenic line derived mL) in diluted aqueous solution to the from resistant larvae collected in an surface of 7-lO mLoflima bean-based apple orchard in Adams Co., Pa. The synthetic diet in plastic eups and al maín objective ofhaving created this lowed to air-dry for 2-3 h. Test larvae

210 Table 1. Plant species used in fitness study for Platynota idaeusalis. ;:c ::> <: Commonname Seientific name Source Variety Family 'Ti III,.., Apple Malus domestica (Bork.). Adams County Red Yorking Rosaceae > ~ o Nursery, Aspers, PA. ? ? 1:-:. Black raspberry Rubus occidentalis L. Miller Nurseries, Allen Rosaceac ..... § Canandaigua, NY...... CD CD Broad-leaved plantain Plantugo major L. B. McPheron house, Plantaginaeeae _-.! Port Matilda, PA :i: ~o -.! Dandelion Taraxacum officinale Wiggers Stokes Sccds, Ine., Asteraceae ~ ~ Fredonia, Ni". ce Domínguez-Gily McPheron were introduced into diet cups in ing semi·synthetic lima bean diet (21). groups of four. The larval exposure AH cages and cups were checkecl eV period to the treated diet was until ery two days for date ofpupation ami pupation or death. eclosiono 'Ibe pupae from all treatments Bioassay_ Larvae used in this were weighed, sexed and transferred experiment were reared on a lima from the cages singly intoplastic cups bean-based artificial diet (21) at 26.7 until adult eclosiono Pupae and adults oC, 60 % relative humidity with a pho were weighed using an electroníc bal toperiodof 16:8 (L:D) h. Fourth instar ance accurate to 0.1 mg. Development larvae (12 days old) were removed from time to pupation and adult eclosion, artificial diet and transferred to each pupal fresh weight, adult dry weight, host to complete larval development. sex ratio andsurvivorship on each host Larvae of the diet treatment were species were measured. transferred to new cups with dieto Lar Statistical analyses. Survivor vae from generation F 19 were used for ship, development time to pupation these experimen ts. andadult eclosion, and pupal and adult Fifty-five 14-day oId larvae were weights were analyzed by two way transferredonto caged, potted ppIe and analysis ofvariance (ANOVA) using black raspberry and 50 onto plantain the Statview statistical program (1) and dandelion in sleeve cages (5 or 10 followed by Fisher' s protected least sig larvae per cage) in a walk-in type nificant difference (PLSD) mean sepa growth chamber. The growth cham ration tests (22). Factors for the two ber was set at 26.7 oC, day length: 16:8 way analyses were diet and sexo Spe (L:D) h and 50-80 % RH. The cages cific comparísons between males and were made of fine pore ny Ion mesh and females within each host were evalu sealed with parafilm. Another set of ated by 2-tailed t-tests. "1. 2 tests were 50 14-day old larvae were transferred used to determine ifthere was depar singly in 28 mL plastíc cups contain ture from an expected 1: 1 sex ratio. Results and discussion

Survivorship. AH insects were specíes (76 % at pupation, 69 % at adult rearedfor 13 days on artificial diet. Any ecIosion) (figure 1). P. idaeusalis difference in survivorship, develop showed the lowest survival rate on ment time, pupal and adult weight dandelion (60 % at pupation, 38 % at occurred after 14 days, the time when adult eclosion) (figure 1). The percent the larvae were transferred to the age oflarvae surviving to pupation and hos~. adult eclosion for black raspberry (74.5 Survival topupation (98 %) and %, 54.5 %) and plantain (68 %, 50 %) adulthood (78 %) was highest on syn had intermediate values. thetic diet-reared larvae (figure 1). Development time. The type Feeding on apple resulted in the high offood consumed by larvae. sex, and est survivorship among the host plant the interaction between host and sex

212 Rev. Fac. Agron. (LUZ). 1997, 14: 207-22:1

-<>- """'" -o- o.l'dIIlion -ó- Black rup -+- PliN"I13I1f1 -+- ~.IM'

,. , 6 , 6 20 U 24 26 28 3D 32

Da..

Data points show survival and development time at pupation. and adult eclosiono lnitial cohort at neonate on apple and black raspberry n ::: 55: dandelion, plantain, and artificial diet n 50. Figure 1. Survivorship curves for P. idaeusalis larvae transferred frOJ.I1 artificial diet onto different diets at 14-days after egg hatch, plotted as the percent of the initial cohort alive at neonate. each had a significant influence on figure 2). Females fed on artificial diet pupal and adult weight, the number developed faster, followed by apple, ofdays from neonate (14 days old) to dandelion, black raspberry, and plan· pupation, and days from 14-day old to tain (table 3, figure 2). Both males and adult eclosion for both males and fe females developed significantly more males, although the main effect of sex slowly than on other hosts (table 3, fig. on days to adult eclosion was not sig ure 2). nificant (table 2), Male lmvae fed dan Host again had a significant ef· delion and black raspberry developed fect on the number of days to adult significantly faster than did their fe eclosion, with sex and the interaction male counterparts in pairwise com between host and sex ratio also signifi parisons (table 3, figure 2), Although cant (table 2). Adult males emerged not significantIy differen t, male larvae significantIy earlier than females from fed apple and plantain developed faster larvae rearedon black raspberry (table than did the females on those hosts 3, figure 3). In fact, males in the arti (table 3, figure 2). Males reared on ar ficial diet and black raspberry treat tificial diet developed fastest to the pu ments emerged first among all hosts palstage, followed by dandelion, black followed by dandelion, apple, andplan raspberry, apple andplantain (table 3, tain. Although not significantly differ

213 Table 2. Two-way analysis ofvarianee indieatingsouree ofvariation, degrees offreedom, F, and P values for data from fitness study of P. idaeusalis. ~ Interaction !3 Source ofvariation Diet Gender (Diet X Gender) f t:' l-.:l dí F dí F dí F @ ~"'"' '< Pupal weight 4.172 16.9*** 1.172 107.9*** 4.172 9.9*** S'::: Adult weight 4.130 10.4*** 1.130 91.3*** 4.130 10.1*** % Ir Days from neonate to pupation 4.173 13.5*** 1.173 13.4*** 4.173 2.4* (J Days from neonate to adult eclosion 4.131 10.7*** 1.131 1.5 4.131 3.7** ::s

* F is significant at P < .05. ** P < .01. *** P < .0001 Rev. Fae. Agron. (LUZ). 1997, 14: 207-223

26~------~

lb 24 b -O- ,A,ppIe -O- Oandeiion 23 --I:r- AtlífiQll diet .~ ~ Planwn i -- I!lICII raspbeny S ¡Z2 Q

20~------~------.-----~ Mala

Figure 2. Interaction line plot of the intluence of dietary host on the mean of days from neonate to pupation for each sexo

a 31

-o- AppIa -O- O_oIion j29 --I:r- BIack rat¡lbitrry :t ~ AnJIioaI

b 27

26 Mar.

Figure 3. Interaction line plot of the intluence of dietary host on the mean days fram neonate to adult eclosiono

215 Dominguez.Gil yMcPheron ent, adult males reared on dandelion have started with similar sex rabos. took longer to eclose than did females More dandelion-fed larvae developed (table 3, figure 3). Females in the black signnificantly into male than female raspberry treatment were one ofthe pupae (table 4). Black raspberry had last to emerge among the five differ the second highest male-biased sex ent diets (figure 3). Artificial diet fe ratio (table 4). Meanwhile. larvae males were the first to emerge among rearedon plantain, artificial diet. and all hosts (figure 3). Feedingon artifi apple yielded abou t the same number cial diet and dandelion resulted in the of males and females. both at pupa fastest development to female adult tion and eclosiono eclosion, followed by apple, black rasp Stephens & Krebs (30) considered berry, andplantain (table 3, figure 3). special features of herbivores that Pupa! and adult weights. Fe make them unusualconsumers. While male pupae weighed significantly more attempting to fulfill their nutritional than males on aH diets (table 3, fig requirements by consumingplant tis ures 4 and 5). Feeding on artificial diet sues andproducts, however, herbivores resulted in the highest female pupal face problems regarding foraging strat weight among aH hosts, followed by egies and being subjected to poten tially plantain, apple, dandelion, and black deleterious factors that may reduce raspberry (table 3, figures 4 and 5). their performance and probability of Pupal weights did not differ signifi survival (29). For example. alleloche cantly among males (table 3, figures 4 micals form one major tine of plant and 5). Adult weights were signifi defense with which herbivores must cantly lower in males than females on cope during both feeding and the artificial diet, plantain, and apple. postingestive processing offood (5. 13, Female adults were heavier when 14,25). Because most, ifnot aIl, plants they were rearedon artificial diet than and plantparts contain both nutrients when they fed the otherhosts (table 3, and allelochemi-cals. the consumption, figures 6 and 7). Black raspberry ap and utilization offood by herbivores peared to have the most detrimental usually involves their interaction (29). effect on female adult weights, result As a result, diets are often character ing in the lowest weights among the ized by partíal consumption of a few different diets for females (table 3, fig or many plantspecies (27) because food ures 6 and 7). Apple resulted in the quality of any one food type is relatively highest male adult weight among the low (when compared with food quality different diets (table 3, figures 6 and forcarnivores), andonefOod type rarely 7). will provide aH essential nutrients for Host effects on sex ratio. Al survival (5, 9, 30). though sex ratio was not known to be The hostplant consumed has an equal at the beginning of the experi influence on survivorship and fitness ment (l4-day old larvae) the individu ofP. idaeusalis. Survivorship and de als were distributed randomly among velopment rates ofP. idaeusalis lar treatments, so the treatments should vae are host specific (I7). This study

216 Table 3. Effect of diet on the mean pupal and adult dry weights, and development times (::1:: SEM; n) ofP. idaeusalis.

Diet Sex Days to pupation Days to ecIosion Pupal weight (rng) Adult dry weight ::t:I (1) (rng) ~ "'%j ¡:l) Artificial diet F 20.4 (0.3; 10) 26.5 (0.2;8) 41.5 (1.1; 10) 7.4 (0.2;9) r.> P-level (t-test) M 20.9 (0.3;26) 27.2 (0.2;23) 24.4 (0.8;26) 3.3 (0.1;20) :> ~ o 0.2821 0.1132 0.0001 0.0001 ? Apple F 23.7 (0.6; 19) 29.3 (0.5:12) 29.8(1.5;18) 5.3 (0.4; 15) "P t:-:)..... P-Ievel (t-test) M 22.7 (0.2;24) 29.0 (0.4;23) 23.9 (0.6;24) 4.0 (0.2;21) ...;¡ 0.1099 0.0035 § 0.7426 0.0001 .- c.o Black raspberry F 24.1 (0.8; 12) 29.8 (0.7;10) 26.1 (1.6; 12) 3.9 (0.4; 10) c.o P-Ievel (t-test) M 22.0 (0.6;29) 27.2 (0.6;21) 21.8 (1.0;29) 3.2 (0.2;21) .-l 0.0414 0.0087 0.0253 0.1014 -~ Plantain F 25.2 (0.5;18) 31.1 (0.7;] 1) 33.1 (l.4;18) 5.4 (0.5;12) No -l P-level (t-test) M 24.3 (0.5;16) 29.6 (0.4; 14) 23.9 (0.9; 16) 3.2 (0.2; 13) ~ N 0.1888 0.0611 0.0001 0.0002 W Dandelion F 24. 1 (1.3;7) 27.5 (0.6;4) 26.2 (2.7;7) 4.3 (0.7;6) P-level (t-test) M 21.1 (0.5;22) 28.9 (0.7; 15) 22.9 (0.7;22) 3.2 (0.2; 13) 0.009 0.3324 0.0977 0.0712 Domínguez-Gil y McPheron

42.5

37.5

~ 3S l!!.. .( 32.5 1 Il. 30

27.5

25 • 22.5 ..

20 t.IaIoI

Means within each sex indicated by the same letter are not significantly different from each other (P < .05, Físher's protected LSD). Figure 4. Interaction line plot ofthe influence ofdietary host on mean pupal weights ofP. idaeusalis males and females. $0

o <5

'0 o l 35 i 30

1 2S

, o MaJe F......

Box is middle 50 % ofobservations. Horizontalline in bOll; is the median. Ehen it is necessary, the boxplot displays the 10th, 25th, 50th, 75th and90th percentiles ofa variable. AH values lor variables above the 90th percentile and below the 10thpercentile are plotted separately. Figure 5. Boxplots ofpupal weights ofP. idaeusalis fed different dieta.

218 Rev. Fac. Agron. (LUZ). 1997, 14: 207-223

7.'

-<>- AR* -O- 0ancIII1on ...::1.- Pl&nlain -<>- Iliad< rupbony -- _alOJet

3.S

b 3 ¡.5.J....--______-_---I

Means wíthin each sex índicated by the same letter are not sígnificantly different from each other (P < .05, Fisher's protectedLSD). Figure 6. Interaction line plot of the influence of dietary host on the mean adult dry weights ofP. idaeusalis males and females. 10 o 11 o

8 o ",", ,~? o aApplo r s l! f§l DanMIion ';5 ~PIanIain ?! " 11 e_rupl:>eny ¡ . ml Artír....IDioot

o F...... MI.M Box is middle 50 % oC observations. Horízontalline in box is the median. Ehen it is necessary, the boxplot displays the 10th, 25th, 50th, 75th and90th percentiles oC a variable. AH values for variables aboye the 90th percentile and below the 10th percentile are plotted separately. Figure 7. Boxplote of adult dry weights of P. idaeusalis fed different diete.

219 Dommguez·Gil y McPherOll

Table 4. Sex ratio for P. idaeusalis reared on different diets. 1

At Pupabon At Adult eclosion

--"~._....~-- Diet n Male:female n Male:female

Apple 42 1.3: 1 38 1.4: 1 Black Raspberry 41 ~.4: 1** 30 2.0:1* Dandelion 30 3.3: 1** 19 3.8: 1** Plantain 34 0.9:1 25 1.3: 1 Artificial diet 49 1.1: 1 39 1.2: 1

1. Sex ratio was not known to be 1: 1 nt the beginning ofthe experiment, but should be similar among diet trentments. *, P < .001. **. P < .0001, by '1.2. demonstrated that P. idaeusalis can tions for P. idaeusalis. Even though, complete development on several host P. idaeusalis survival is lower when plants and that difierent hosts led to the insect feed on weeds (dandelion and different developmental outcomes. plantain) or surrounding vegetation Groundcover weeds and wild hosts (black raspberry), feeding on those adjacent to cultivated orchards have hosts could still have important con the potential to serve as reservoirs of tribution to the pest population in the P. idaeusalis populations (lO, 12, 19). orchards. Artificial diet proved to be the Developmental time on dandelion best host for P. idaeusalis survivorship was about the same as apple-fed lar and for all the developmental param· vae. whereas larvae feeding on plan eters studied in the present study. tain had the 10ngest time taken to pu Felland & Run (13) reported that lar· pation and adult eclosion among a11 vae reared on artificial diet survived diets. In the field prolonging the de better, developed faster, andproduced velopmental perlod mightrepresentan heavier male andfemale adults. David importantfactor for fitness reduction et al. (lO) also showed that P. and affect the nutritional suitability idaeusalis developed fas ter on semi· ofthe host plant, the susceptibility of synthetic diet compared to feeding on the larva to predators and parasitoids, excised leaves of strawberry, apple, the availability ofmates, andprolonged and dewberry in the laboratory. exposure to abiotic factors. Female lar Among hostplants, survivorship vae reared on black raspberry emerged was highest when feedingon apple and 2.6 days later than males, compared lowest on dandelion. Black raspberry with 0.3 days for apple-reared P. andplantain display intermediate val idaeusalis. In the case ofplantain·fed ues in both survival at pupation and larvae, females emerged 1.5 days later at adult eclosion (figure 1). than males. TIle difference in total TIlis finding has control implica development time between the sexes

220 Rev. Fae. Agron. (LUZ). 1997, 14: 207-223 might lead to a shortage ofmales for more, Hunter et al. (18) found that the female moths developing on black rasp relationship between larval density berry or plantain in nature. and phloridzin concentration varied Larvae reared on plantain pro among leaftypes. Larval den sities on duced the heaviest pupae and adult shoot leaves increased as phlorídzin females among the host plant specíes, concentrations in those leaves in followed by apple, dandelion, and black creased in the first generation. How raspberry. These results indicate that ever fruiting spurs supported higher extendeddevelopment of plantain-fed larval den sities than either nonfruiting female larvae allows them to grow spurs or shoot leaves. somewhat larger and form heavier Host effects on individuallarvae. pupae; pupal weight directly correlates such as those reported here, and by with higherfecundity in terms of num Felland & Hull (l3), Simelane (29), ber of eggs produced for other lepi Hunter elal. (18). are undoubtedIy inl dopterans (8,16). portant factors affecting P. idaeusalis These results are thus consistent in nature. P. idaeusalis can feed on with those ofSimelane (29), who also many different host plants, leading to determinedthat apple andcherry were different rates of development, fitness, not significantly different from one and mortality. Such effects must be another in developmental time taken considered in studies ofthe population to pupation and adult ec1osion or pu dynamics ofthe insect over large ar pal weights. Exc1uding the synthetic eas. diet, which resulted in the best perfor Therefore, additional studies are mance, P. idaeusalis larvae feeding on needed to determine P. idaeusalis peach developed fastest and achíeved population biology outsíde of apple. on the highest pupal weights, whereas groundcover within orchards, and on larvae feeding on cherry took longer duferent apple cultivars. This knowl to develop and had the lowest pupal edge could be useful in timing ofcon· weight. Survivorship was highest trol actions. when feeding on apple and lowest on Since fruit production is ínter peach. Simelane (29) used a similar mixed in Pennsylvania, the variabil methodology (potted trees) and the ity in the lífe cyc1e ofP. idaeusalis will same setofenvironmental conditions. be high due to the many host species Hunter et al. (18) reported that available. Recommendations for the densities ofP. idaeusalis larvae var timing of control applications due to ied significantIy in both larval genera the different phenologies will have to tions among leaftypes within trees and be more refined if the selection pres among cultivars. The highest densi sure which results in the development ties ofP. idaeusalis were observed on ofresistance is to be reduced. For ex 'Delicious' and lowest on 'Yorking,' ample, insecticide spray programs may while terminal shoot leaves supported have to be adjusted to take into ac higher larval densities than either count the delayed emergence due to fruiting or nonfruiting spurs. Further- feedingon plantain.

221 Dominguez-Gil y McPheron

Literature cited

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