THE BEQNGMICS AND CGNTROL 0F SROBASi—S TRICGLORELLA {é’yraiidaa Lepidoptera} 1N TAR? CHERRIES {N MICHBGAN
Thesis for the aggree cf M. S‘ MECHEGAN SYATE UMVERSITY PAUL EBWARB BGLDT 1987
THi-Jbs 2,; u' LI B RA 32. 1" i I‘dichigan State ‘ Lg. Umwrcizy fl
L“"M*-’~-W THE BIONOMICS AND CONTROL OF ACR OBASIS TRICOLORELLA (PyralidaezLepidoptera)
IN TART CHERRIES IN MICHIGAN
BY
Paul Edward Boldt
A THESIS
Submitted to Michigan State University in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE
Department of Entomology
1967 T1
Howitt in
study.
granting
graduate
Ethelbel
Sp insect p;
James E
Dr, How
ACKNOWLEDGEMENTS
The author wishes to express his appreciation to Dr. Angus J.
Howitt for his advice and assistance throughout the duration of this study. The author is grateful to the Department of Entomology for granting financial assistance in this period and to the members of the graduate committee Drs. Gordon E. Guyer, James E. Bath,
Ethelbert C. Martin, and John L. Lockwood.
Special thanks to Drs. Paul H. Wooley, for his advice on fruit insect problems, Dean L. Haynes, for his statistical assistance,
James E. Bath, for his editorial assistance in the absence of
Dr. Howitt; and to Phillip G. Coleman for his photography.
ii LIST OF
LIST OI
LIST OI
INTRO}:
REVIEV
METHO
EXPERL
Ident
Lif e TABLE OF CONTENTS Page LIST OF TABLES iv
LIST OF FIGURES
LIST OF PLATES vii
INTRODUCTION
REVIEW OF LITERATURE
METHODS AND MATERIALS
EXPERIMENTS, RESULTS AND DISCUSSION 12
Identification and Distribution in Michigan 12
Life Table Studies 14 Egg stage 14
Firsbinstar to third-instar larva stage 14
Third—instar larva to pupa stage 21 larval development 38 feeding sites and population estimate of emerging larvae 39
Papa stage 42
Adult moth stage 46
Second generation stage 57
Timing According to Stages of Bud Development 59
Chemical Control 63
Spring applications 63
Summer applications 67
SUMMARY 72
LITERATURE CITED 75 iii I'l‘lliI LIST OF TABLES
Table Page
Analysis of variance of first- to third-instar larval infestation of tart cherries Hart, Michigan - July 11, 1967 18
Larval mortality (first- to third—instar) of Acrobasis tricolorella in tart cherries Shelby, 1966 and Hart, 1967 -
Ivfichigan 19 Acrobasis tricolorella larval emergence from tagged
hibernaaila in tart cherry orchards, Michigan - 1966 22
Analysis of variance for linear regression 40
Simple correlation results between trunk diameter, tree height, crown diameter, height and area, and number of bud clusters of tart cherry trees Hart, Michigan - 1967 4O
Hourly flight patterns of the adult Acrobasis tricolorella as determined by trapping with black light at Acme, Michigan - 1966 49
Number of Acrobasis tricolorella adults which emerged
from three funnel trap grids Hart, Michigan - 1967 50
Effect of various insecticides applied to tart cherry in the delayed dormant stage on Acrobasis tricolorella third- to fifth—instar larvae Shelby and Lake Leelanau, Mchigan - 1966 66
Effect of various insecticides as preharvest applications to tart cherries on Acrobasis tricolorella larvae Lake Leelanau, Michigan - 1966— 69
10. Effect of various insecticides as preharvest applications to tart cherries on Acrobasis tricolorella larvae Hart, Michigan - 1966 69
ll. Effect of various ultra low volume-applied insecticides as preharvest applications to tart cherries on Acrobasis tricolorella larvae Hart, Michigan - 1966 70
12. Effect of various insecticides as preharvest applications to tart cherries on Acrobasis Wlarvae Hart, Michigan - 1967 70
iv Illllfli; .-.m.n Pa.w e
LIST OF FIGURES
Figure Page
Distribution of Acrobasis tricolorella in the major tart cherry producing counties of Michigan - 1966 13
Infestation of tart cherries by first- to third-instar Acrobasis tricolorella la me as determined by twice a week sampling, Oceana County - 1966, 1967 16
Factors responsible for overwintering Acrobasis 1W3 larval mortality - 1966, 1967 23
Occurrence of A r a 's Warval emer- gence from hibernacula, migration and pupation in the soil Hart, Michigan - 1967 27
Occurrence of Wtflmlgmflilarvae observed at intervals in quadrants containing tagged terminal bud cluster replicates Hart, Michigan - 1967 29
Occurrence of W W larvae in damaged bud clusters collected at twice weekly intervals as related to bud development, Oceana County - 1966, 1967 31
Proportion ongmbaflLtmglgmla larvae observed as dead in tart cherry samples collected at twice weekly intervals, Oceana County - 1966, 1967 34
Trapping of MS Wmature larvae and emerging adults by funnels Hart, Michigan - 1966 35
Relation between the number of bud clusters per tree and the trunk diameter of the tree in tart cherry Hart, Mchigan - April 18, 1967 41
10. Seasonal adult Acrobasis tricolorella flight as determined by trapping with black light Shelby, Mchigan - 1966 52
11. Seasonal adult ACME. txisalamlla flight as determined by trapping with black light Acme, Michigan 1966 53 12. Seasonal adult Acrobasis tricolorella flight as determined by trapping with black light Lake Leelanau, Mchigan - 1966 54
13. Seasonal adult Acrobasis tricolorelfia flight as determined by trapping with black light Hart, Michigan - 1967 55
14. Seasonal adult Acrobasis tricolorella flight as determined by trapping with black light South Shelby, Michigan- 1967 56
15. Seasonal adult Acroba sis tricolorella flight as determined by trapping with black light Acme, Michigan - 1967 57
vi
Plate “#4—
LIST OF PLATES
Plate Page
Stages in the life history of Acrobasis tricolorella showing: (1) hibernaculum in crotch of cherry twig (Z) fourth instar larva in Opening buds (3) feeding damage to buds (4) fifth instar larva at full bloom stage (5) leaf nest of second generation larva (6) pupae. 60
Stages in the life history of Acrobasis tricolorella showing: (7) cocoon (8) adult (9) egg (10) fourth and fifth instar larvae (ll) injury to fruit by second instar larva (12) cherry fruit Split open showing feeding of second instar larva (13) injury to fruit by third instar larva. 61
Stages of bud development in tart cherry showing: (1) early greentip (2) late greentip (3) delayed dorment (4) full bloom (5) bud separation (6) shuck split. 64
vii L
ripened
infe stat
Oceana
section
cherrie holes a
A
Under 5 hla pr<
Therefl industi-
515,03
A
Severa their 0 cOntl‘ol
1966 a: bio,10th
J popUIa1 obServ INTRODUCTION
Larvae of the moth Acrobasis tricolorella Grote infested
ripened tart cherries in Michigan during the summer of 1965. The
infestations were located in the major cherry-growing areas of
Oceana, Grand Traverse and Lake Leelanau Counties in the northeast
section of the Lower Peninsula. The larvae burrowed into the
cherries, left small amounts offrass and webbing at their entrance
holes and discolored the flesh of the cherries.
A single larva in a load of cherries constitutes adulteration
under State of Michigan Law Act 86, Public Acts 1929 and may result
in a processor's rejection of an entire cherry crop from one orchard.
Therefore, this insect posed a threat to the Michigan tart cherry
industry whose total production in 1964 was 190, 000 tons valued at
$15, 039, 000. (Michigan Agricultural Statistics, 1966).
At that time, no satisfactory control measures were known.
Several growers applied various organic phosphate insecticides to their orchards after observing infested fruit, but this did not provide
control.
The purpose of this study, which was initiated in the spring of
1966 and completed in the summer of 1967, was to determine the bionomics of _A_:_ tricolorella by field observations, cage studies and population density estimates. The life cycle of _A_._ tricolorella as
observed in this study was used to determine possible stages in which the ins« control first in gence f achievi these 5 the insect might be susceptible to organic phosphate insecticidal control. Several insecticides were evaluated against the eggs, the first instar larvae, the larvae within the fruit, the larvae after emer- gence from the hibernacula and the adult moths. Methods of achieving the critical timing necessary in spray applications against these stages of the insect were evaluated. Grote Maine. hadthe appear: nude as upon caster; it as on "10th adull: the frOm Forbe BQEES
Was
the fru. an in:
b-
a
(1 I-i
<
1 1 I? REVIEW OF LITERATURE
Acrobasis tricolorella was described as a new species by
Grote (1878) from two male moths on an unknown host, Oldtown,
Maine. Moths collected in Colorado were described as a new species,
Mineola scitulella, by Hulst (1900); these were the same size and
appearance as _A_ tricolorella but had a much brighter coloring and
had the outer cross line of the forewing edged outwardly with dull-red.
Heinrich (1956) has fully described the external anatomy of both male and female moths. He classified Acrobasis tricolorella Grote
as the senior synonym of Mineola scitulella Hulst as western and
eastern specimens could not be distinguished; the color detail relied upon by Hulst for the separation of_M_. scitulella did not hold because it was found in both specimens and varied equally in both.
The insect has been commonly described as an economic pest on fruit under the name __M_. scitulella, the destructive prune worm.
Forbes (1923) and Heinrich (1956) reported that the insect ranged from Quebec and Maine to California. Newcomer (1919) first found the insect on apples in Washington whereas Pack (1930) reared the adult from larvae found on wild chokecherry and wild plum in Utah.
The first study of this insect's biology and a description of its stages was compiled by Shull and Wakeland (1941); they collected the moth from an unknown host in Idaho in 1921. It was first reported as an economic pest attacking prunes in Idaho in 1925; by 1930 they had obse
Oregon. hibe rna- maturir. adeun partial
I
(Houki descri larvae
Prune
Oatnaa
and 0} and d.
IOund
fOrmi 4 had observed its presence in both southwestern Idaho and southeastern
Oregon. This pest overwintered as a partially grown larva in a hibernaculum and emerged during March and April to feed until maturing. Pupation occurred in the soil and moths emerged in May and June to deposit eggs on the underside of leaves. A second and a partial third generation were observed in Oregon and Idaho.
In 1949, the larva was present in tart cherries in Michigan
(Houk 1950) and in Wisconsin (Dever 1953) presented a complete description of the egg and the mature larva and found that the larvae pupated in the soil and had one generation a year.
Newcomer (1950) reported that the insect was a serious pest of prune and cherry trees in southern Idaho and in part of Oregon.
Oatrnan (1964) reported considerable larval damage to cherry buds and observed that adults emerged four to five weeks after petal fall and deposited eggs on the lower surfaces of the leaves. He also found that newly emerged larvae fed in the ripening cherries before forming hibernacula.
Chemical control of A: tricolorella has not been successful in the past. Haegele (1932) reported promising results with sprays containing pyrethrum; nicotine sulphate was partially effective but only above 70° F. In addition, both materials were effective only when applied early in the spring when the buds were swelling, in green-tip, and just before they had begun to whiten. Newcomer (1950) stated, "No satisfactory measure for controlling this pest has been worked out, although an early application of DDT, before the trees bloom, may be effective. " ,—
.a—————-".——~ At
several insuffici experim
injury b.
in Antri
Re
Wakelan
larvae v
not indl
Damian
Cherry
this pes
Attempts by Dever (1953) to evaluate the effectiveness of several spring-applied insecticides were unsuccessful since an insufficient infestation occurred in the untreated plots in each of two experiments. Hough (1951) found no difference in the amount of injury between control and chemical treatments in tests conducted in Antrim county, Michigan.
Research in the area of biological control has been neglected.
Wakeland (1930) stated that approximately 10% of the _A_. tricolorella larvae were parasitized by six species of Hymenoptera, but he did not indicate whether spring or summer larvae were parasitized.
Oatman (1966) determined that 1. 5% of the fruit injury to a tart cherry orchard in the absence of insecticide sprays was caused by this pest in competition with other insect populations. Sex
new hibeq
The orch area of h l Th4 were as
METHODS AND MATERIALS
Seven Montmorency tart cherry orchards infested with A; 31i- colorella were selected for study purposes on the basis of evidence of new hibernacula, history of previous infestations and poor management.
The orchards were selected in two of the three major cherry-growing area of Michigan.
The locations of the experimental orchards in Oceana County were as follows:
Shelby Township, Section 15, Woodrow Road
1 mile east of Shelby
Hart Township, Section 18, Tyler Road
3/4 mile west of Hart
Hart Township, Section 15, Tyler Road
1 mile east of Hart
Hart Township, Section 20, Old U. S. 31
1/2 mile south of Hart
The locations of the experimental orchards in the Grand
Traverse Bay Area were as follows:
Peninsula Township, Grand Traverse County, Section 5,
Peninsula Road
Milton Township, Antrim County, Section 18
Bussa Road
Acme Township, Grand Traverse County, Section 18
Yuba Road
Lake Leelanau Township, Lake Leelanau County, Section 15 6 E wmfld. as infe
(Dever relatec
1966 a were1 pOpUIa
cages cage. into a
CoVer
VOIun globe c10th.
matu:
galva liner Several sites were used as it was anticipated that not all sites would contain a sufficiently high population for experimental purposes as infestations of the destructive prune worm are localized and erratic
(Dever, 1953). After larval emergence from the hibernacula, studies related to biology were limited to the Shelby and Acme orchards in
1966 and to the Hart, Old U. S. 31 orchard in 1967. The other sites were used for chemical control studies or rejected due to low insect populations or heavy freeze losses.
Moth fecundity was tested with the use of three experimental cages - a wire-sleeve cage, a cloth covered cage and a lantern globe cage. The sleeve cages were constructed of wire screen and shaped into a cylinder 30 inches long with an 8-inch diameter; the ends were covered with cheese cloth. Cloth-covered cages were one foot3 in volume and framed with l x 1 inch pieces of wood. The glass lantern globes were 3 inches in diameter and covered on the top with cheese cloth.
Eighty wire funnel traps were constructed to both sample the mature larvae that dropped from bud clusters of the tree to pupa in the ground, and trap moths. The traps were constructed of 1/8-inch galvanized screen shaped into a shallow funnel. This type of screen was used because it was inexpensive, rigid and could support a paper liner which was stapled to it. The seams of the funnel were soldered together and a canning jar ring was soldered to the small opening at the base in such a way that a l/Z-pint jar screwed into it would catch any material falling into the funnel. The size of the ring was larger than theft
The h
10 inc
wa s s
carefi
Specie
liner
Sticku
isobut
81'0um
It alsc
PUTPO:
screel
the ed
ducted
Hibe r:
infeste talit)’ a with a equippc Ohio. 8 the funnel opening to reduce the possibility of losing the trapped insects.
The funnel diameters were 31 inches and 1. 5 inches and the height was
10 inches. The trapping area equalled 1/10, 000 acre. A paper liner was stapled tightly to the inside of the funnel. Seams of the liner were
carefully stapled to prevent larva escape. A sticky substance, Stickum
Special, was placed in a 2-inch wide band around the outer edge of the liner and along the paper seams to prevent larvae from crawling away.
Stickum Special is a viscous material consisting of polymerized butene, isobutene and inert materials manufactured by Mickel and Pelton
Company, Emeryville, California.
When the funnel trap was upright (with the jar in a hole in the ground) it served to collect larvae that fell from the buds to pupate.
It also was used to trap moths as they emerged from the soil; for this purpose the trap was inverted and the paper liner was replaced with a screen liner. The moths crawled up the sides of the funnel and were trapped in the Stickum coated jar at the top. No space existed between the edges of the funnel and the soil.
During 1966, detailed observations and cage studies were con- ducted to determine fully the life cycle of this economic pest in Michgan.
Hibernacula were tagged and observed for larval emergence, and infested bud clusters were sampled to determine larval growth, mor- tality and pupation. Adult flight was determined by black light trapping with a motor—driven Spinsect, an 8-inch circular 15 watt black light equipped with a fan, manufactured by Ampsco Corporation, Columbus,
Ohio. Ovipositional experiments were conducted in glass globe cages. and.in negle<
interv are a:
0f egg
Popuh
Cherr dQIEr]
{TQm aISo ‘ and b' 9
Infested cherries were sampled to determine larval growth, mortality and feeding duration.
Research in 1967 was repetitious of the previous year's methods and included population sampling in an unsprayed 40-tree block of a neglected 30-year old tart cherry orchard at Hart on Old U. S. 31 Road.
The life cycle of A. tricolorella can be divided into five age-
intervals. The intervals and the methods used to study each interval are as follows:
1) Ess
Leaves removed from trees were observed for the presence of eggs.
2) First instar to third instar larva
The relative density of young larvae was determined by population sampling of the ripened cherries. Samples of infested cherries removed and dissected under the binocular microscope determined larval growth and mortality.
3) Third instar larva to pupa
Hibernacula were tagged in the fall and observed in the spring to establish larval emergence and overwintering mortality. The larvae from these hibernacula were observed through pupation. This interval also was sampled by tagging bud clusters before emergence occurred and by recording at intervals the presence of any larvae found within them. 4) larvae d ground c were pla 5)‘
and peal.
iemale
InSeCtlt
emerge
8Plays
develo;
the m0}
concent
John Be
ULV eq
COncenr less at
Were C,
Where 10
4) Pupa
Funnel traps placed upright under the trees collected mature
larvae dropping to pupate. These traps when inverted directly over the
ground collected adults as they emerged. Pupae from caged larvae
were placed in shell vials to determine duration of pupation.
5) Adult
Black light traps were used to determine incipience, duration
and peak of adult flight. Fecundity was determined by caging male and
female moths on twigs of foliage.
Chemical control studies were conducted in 1966 and 1967.
Insecticides applied in the spring were timed to follow closely the
emergence of larvae from their hibernacula. The application of these
sprays coincided with the early delayed dormant stage of cherry bud development. Summer or preharvest treatments were applied against the moth following its occurence in the black light traps.
Three to six insecticides were applied with varying chemical
concentrations in each experiment. Applications were made with a
John Beam blower, hydraulic gun and ultra low volume sprayer. The
ULV equipment is a new development in the ground application of
concentrated pesticides (Howitt and Pshea, 1966).
Applications were made when the winds were 5 miles per hour or less at a tractor speed of 2-1/2 miles per hour. Both sides of the trees were covered except for the delayed dormant applications at Shelby where the effectiveness of spraying every other row was evaluated. The contrc replicatior
11
The control blocks were not sprayed. End trees in the row in all replications were not evaluated.
ldenti
Count theU
Pyra]
trees
Crane
1966 grow limit (Fig, tart,
Bure
Spec;
Were EXPERIMENTS, RESULTS AND DISCUSSION
Identification and Distribution in Michigan. -
Specimens of the adult collected from Shelby Township, Oceana
County, Michigan in 1966 were identified by Dr. D. A. Duckworth of the U. S. National Museum as Acrobasis tricolorella Grote (Family:
Pyralidae ).
During 1966 A. tricolorella larvae were observed in Oceana
County, Michigan on Napoleon and Schmidt varieties of sweet cherry trees. Damaged fruit also were observed on the Windsor variety in
Grand Traverse County.
No prune trees were found to be attacked in Oceana County during
1966 or 1967 although prune is known to be a host of the insect in fruit growing areas of the western states.
Distribution of the moth on tart cherries in Michigan Counties is limited to the northwest and north-central part of the Lower Peninsula
(Fig. 1). Daily catches from black light traps located in unsprayed tart cherry orchards at Oshtomo, Berrien County and Lawrence, Van
Buren County were examined from May to July, 1967. No adults of this species were collected. Several orchards and fruit pick-up stations were visited during the peak of harvest, but no fruit infested by A. tricolorella larvae were observed. It is concluded that the insect is not
in the southern or eastern parts of the state although there is a concen- tration of tart cherry orchards in those areas. The density of the infestation is highest in the center of Oceana County and extends into the southern part of Mason County. It is less concentrated in the three
12
HURON
MICHIGAN
LAKE
‘ ..... «a o u.- .- ......
LAKE
o . .A I .o .‘.-'- ' .u ." u . '- ' Ill... ". .,..-,....'. a . . .ao‘. .. o. _ II .l-g'...... , . ..o' . .. . 0...... - . 0 ~ ,- ~I'. ,. ..._ L . ~ . ‘ u . . . ~- w- . . I n . . - .Io 0 -. .,.. ..-. u n .._. . ou. ~- -. . ._ a n -.- .. , . . n n . 0. O n I I 0-. n o u- 0'. iNfilANA
O 50 lg
Scale in miles
Figure l. -Distribition of Acrobasis tricolorella in the major tart cherry producing counties of Michigan - 1963 *
l3
14 county Grand Traverse Bay Area; total cherries damaged and number of insects per orchard also were less numerous in that area. During this study, no hibernacula or larvae were found in Charlevoix, one of the two counties initially infested in 1950.
Life Table Studies. -
Egg Stage. -
Eggs were observed primarily under bud scales, around leaf scars and new buds. Only a few eggs were laid on the undersides of the leaves as stated by Shull and Wakeland (1941) and Oatman (1964), as shown in Plate 11-9. As the eggs neared occlusion, small black circles developed beneath the chorion; these probably represented the develop- ing head capsules of the larvae.
Leaves were removed at random from trees in the research block in an attempt to determine egg density, mortality and rate of hatching. This was unsuccessful as the eggs were not to be found in the expected numbers. Observations of caged adults showed that most eggs were laid in protected areas around leaf scars and new buds; sampling of the fruit spur would more accurately indicate egg density.
First instar to third instar larva stag . -
Observations were made in 1966 and 1967 on larvae found in the nearly ripe fruit. Cherries exhibiting damage typical of that caused by the num
A cherr
frass ar L: on July due to a
to ident
‘
4
#3 15
_A, tricolorella were collected at intervals and examined to determine
the number and stage of larvae present; mortality also was recorded.
A cherry was considered damaged if it contained an entrance hole, frass and/or webbing that is characteristic of _A. tricolorella larvae.
Larvae were first observed infesting the fruit in Oceana County on July 5 in 1966 and on June 23 in 1967. This variation probably was due to an earlier adult emergence in 1967 and to the observer's ability to identify the presence of larvae in the cherries at an earlier stage of development.
The similarity in percent of larvae present within infested cherry samples in 1966 and 1967 is shown in Fig. 2. A rapid drop in the number of larvae present between July 8 and 12 of both years corre- sponded with initial observations of hibernaculum formation in the orchard on July l2 in 1966 and followed the presence of hibernacula on
July 6, 1967. The interval between the first observed larva in the cherries and the first observed hibernaculum formation indicated that the minimum number of days during which larvae feed in the cherries varied between four and 11 in 1966 and 14 and 20 in 1967. This discrepancy was due in part to observations of an earlier stage of larva infestation in 1967.
The fruit in the research orchards was harvested by the owners in both years between July 19 and 28. It was evident that although the majority of larvae had left the cherries by this time, some were still found in the picked fruit. A delay in harvesting of a few days would avoid this problem although the damaged fruit would still be present. 30 Acrobasis
Oceana
28
25 T sampling,
third-instar
II meal to
week l6 a
first-
II l4 by
twice
II IIIZ
by
II 89
cherries
II 56 tart determined
of
I JULY
as
1F 30
1967.
l 26 larvae -Infestation
1966, r
23 - 2.
P
JUNE
2| 0
IO' 60' 2O 3O
90f”
IOO County Figure
anus-I bugugoiuoo sauuaqo paoomoa % tricolorella
16 17
This explains why chemical applications of carbaryl may appear to be effective when applied during harvest. In reality the chemical was not able to penetrate the skin of the fruit, but the delay in picking coincided with emigration of the remaining larvae.
The relative population density was determined in 40 trees on
July 11, 1967 by counting the number of infestations per 25 randomly selected cherries in each of the four quadrants of the tree: south-lower, south-upper, north-lower, north-upper. To determine variation between the tree quadrants an analysis of variance (Li 1964) was computed using four quadrants as treatznents and 40 trees as replications. The mean number of infested cherries per 25 samples and their standard deviation for each quadrant as counted on July 11 were:
south-lower 2. 975 _-l_-_ 3. 162 south-upper 2. 850 i l. 754 north-lower 2. 675 i l. 752 north-upper 3. 550 i 2. 655
There was no significant difference between the infestations among the four quadrants indicating that females probably oviposit randomly throughout the tree (Table 1). There was a significant difference between densities in trees, an indication that a factor exists which influences the female in selection of certain trees for oviposition.
An estimate of the relative population density, assuming that one infested cherry contains one larva computed from the sum of all the quadrants, was 12. 12% infestation or 485 larvae per 4000 cherry samples. An evaluation of infestation in 10 unsprayed trees located in another section of the orchard agreed closely with the above larva -—-——--* ’—I—-i
. _—-—-—_—_ ___.__ _..._.___._,_.
peri01 oftart Table' Source a Quadr Trees densi fOrm‘. Error insta; fruit thatC Total Cher; soumh Show. (Tabl gra. Table 1. -Analysis of variance of first-to third-instar larval infestation of tart cherries, Hart, Michigan - July 11, 1967
Source SS DF MS F Sig.
Trees ' 444. 72 39 ll. 40 2. 7142 . 05
Quadrants 17. 22 3 5. 74 l. 3666 n. 8.
Error 491 l 17 4. 20
Total 953 159
density. One hundred randomly selected cherries in the north and south halves of each tree were counted. Two hundred nineteen of 2000 cherries or 10. 9% were found to be damaged.
Mortality of larvae feeding in the cherries was much higher than that of spring larvae. Two of the seven larvae collections in 1966 showed a relatively high mortality of 23% on July 5 and of 33% on July 14
(Table 2). The former date corresponded to the initial infestation of the fruit by first instar larvae. Mortality on July 14 of second and third instar larvae corresponded to larva migration to sites of hibernacula formation. The reasons for this mortality are not known.
No early mortality was recorded in the eight collections in 1967 but a gradual increase in the proportion of dead larvae occurred from
June 30 to July 11. This peak of 29% coincided, as in 1966, with the period of greatest migration out of the cherries.
l8
7/16
”~——
*
— Table 2. -Larval mortality (first- to third-instar of Acrobasis tricolorella in tart cherry samples, Shelby, 196 and Hart, 1967, Michigan
No. of larvae % Mortality
Egg;
6/23 10 0
6/26 12 0
6/30 48 12
7/3 50 15
7/6 44 22. 5
7/11 48 29. 5
7/14 52 23
7/21 38 12
Shel 7/5 16 24 7/8 21 11
7/12 27 10
7/14 18 33
7/16 12 0
7/20 8 13 7/25 2 0
l9 20
While the time of larval mortality was unknown, it was apparent that first-instar larvae and larvae about to form hibernacula were most susceptible to factors influencing mortality. During the latter period, larvae of Rhmletis cingulatus Leow and of Conotrachelus nenupliar
Herbst were observed infesting the fruit. The influence of their compe- tition for feeding sites on the mortality of A. tricolorella was undeter-
mined, but it was expected to be significant.
Observations of larvae in the cherry trees revealed that they began to feed near the stem of the cherries and burrowed irregularily toward the pits. They continued to feed around the pits and each formed a small pocket in the tissue near the distal end of the cherry it was infe sting.
Larvae have been seen burrowing out through the side of one cherry into the side of another in the same cluster; thus, four or five cherries could be injured by one larva (Plate II-l3). Infested cherries were occasionally tied together or to leaves by webbing or frass.
When the larva was not found, the presence of frass was used as an indicator of infestation. The presence of a larva may cause the cherry to ripen more quickly and to be more susceptible to brown rot than an uninvaded cherry.
The larvae appeared very nervous, and when disturbed they quickly came to the surface of the cherry and dropped to the ground. Vibration during transportation of lugs of cherries from the orchard to the processor brought the larvae to the top layer of fruit. 21
Third-instar larva togupa stag_. -
A minimum of 50 hibernacula (Plate I-l) in each of seven tart cherry orchards was tagged and observed at twice weekly intervals for larval emergence in 1966. The date and location of each hibernaculum and of each newly emerged larva was observed and recorded on an orchard map.
Eighty hibernacula were tagged at Hart in the fall of 1966 and observed at intervals for larval emergence the following April. As in the previous year, data were taken on the development of blossom buds, especially as related to larval emergence.
Tagged hibernacula were removed from trees in both years when it was obvious that no larval emergence would occur. Hibernacula found to be intact were dissected under a binocular microscope and the larvae within were separated into three easily recognizable categories:
a. Parasitized - pieces of larval head capsules and a thoracic shield were present, or the parasite was present.
b. Fungus covered - larvae were covered with fine white mycelial strands of fungus.
c. Unknown - some larvae were flaccid and shriveled while others were firm and of normal size for third instar larvae.
Another factor affecting mortality, missing hibernacula, was added in 1967 when hibernacula tagged in the fall of 1966 had become dislodged by spring.
Some hibernacula were placed in a glass lantern globe in an attempt to collect adult parasites. Table 3. - Acrobasis tricolorella larval emergence from tagged hiber- nacula in tart cherry orchards, Michigan-1966
Date Shelby West Hart East Hart
4/23 19 20 12 4/24 11 4 7 4/28 1 3 2 5/ l l l 1 5/4 0 0 1 5/7 0 0 0
Total larvae 32 28 23 Total hibernacula 73 41 52 “/o Emergence 44. 4 62. 2 44. 2
Date Milton Acme Peninsula Lake Leelanau
4/ 24 14 13 -a -3 4/25 21 0 3 0 4/29 3 5 0 0 5/2 1 2 O 0 5/3 0 0 0 0 5/5 0 0 Z 0 5/7 0 0 0 3 5/16 -a -3 o 4 5/21 3 3 o 3
Total larvae 39 20 5 10 Total hibernacula 56 48 39 58 % Emergence 69. 6 41. 7 12. 8 l7. 2
3' no observations this date
In 1966, initial larval emergence occurred between April 21 and
April 24 in six orchard locations and was nearly complete in five of these locations by April 25 (Table 3). The majority of the flower buds in the seven orchards were entering the delayed dormant stage of development. The delay in emergence at Lake Leelanau coincided
22
-
mortality
UnknoWn
infested
Fungus
Parasite larval
Hibernacula missing
' ‘
\ ,
3
V1 D
67
-
tricolorella
Hort I966
_A_crobasis
-66
......
SW5.“
Leelanau ~.‘).“.:.
I965 Lake
overwintering 66
T—
for
-
"-3
...- .....
'I
Shelby I965
responsible
Hort
~—
1965-66
West
-Factors
3. 1967
L- —
25 20
35-
30- 1966, Kmououl was led Figure
23
24
with an equal delay in bud growth. Lake Leelanau and Peninsula,
which also had delayed development, were those locations with a low
rate of larval emergence. Larval emergence at Lake Leelanau
occurred between May 5 and May 20. This 3-week delay probably was
due to localized unseasonably cold weather during April and to 'the
geographic location of Lake Leelanau County, 450 North Latitude.
Larvae emerged from 41. 7% (17. 2-62. 2%) of the 378 hibernacula
tagged in the seven orchards.
Larval emergence at Hart in 1967 was first observed on
April 11, 13 days earlier than in 1966 and continued through April 18.
The greatest number of larvae, 63% of the total which emerged,
appeared between April 11 and 14; emergence occurred from 48. 1%
of the 80 hibernacula.
While disease organisms and other factors affected about the
same number of hibernacula in each orchard, the amount of
parasitism varied widely and had the greatest effect on larval
survival. Mortality during the winter of 1965-66 varied from 37 to
80% between the 3 test orchards (Fig 3). The highest mortality
occurred at Lake Leelanau and was accompanied by the highest
number of parasitized larvae. The lowest mortality, at Hart, also
was that accompanied by the lowest number of parasitized larvae.
In 1966, larval, pupal and adult parasites present in the hibernacula were preserved in 85% Ethyl alcohol and sent for identification to Dr. B. D. Burks of the Insect Identification and
Parasite Introduction Research Branch of the Agricultural Research 25
Service, United States Department of Agriculture. Representatives
of two families of Chalcidoidea (Order: Hyrnenoptera) were identified:
Eupelrnidae: Two males, one pupa and one larva were identified
as probably Eupelmus _s_p.
Pteromalidae: One female was identified as Capgllia
lividlcormis (Girault). Fourteen pupae and prepupae were probably
members of this family.
Larvae containing mycelial strands of fungus were sent to
Dr. S. O. Poiner, Division of Invertebrate Pathology, University
of California, Berkeley for examination in 1966. Specimens
were found to contain several saprophytic fungi of the family
Dematiaceae none of which was responsible for the larval deaths.
A check which proved negative also was made for virus by water-
ether-carbon tetrachloride extraction. The cause of death was non-microbial but may have been aborted parasitism followed by
invasion of saprophytic fungi.
As shown in Fig 3, absolute mortality in a population of 80 overwintering larvae at Hart, 1966-67 was 46. 3%. This included the 6. 3% which had become dislodged from the tree before the first observation in April. Parasitism was observed in 21. 3% of the dead larvae. Two parasite pupae were recovered but could not be reared to adults. Seven and a half percent of the larvae contained a fungal growth similar to that observed in 1966. Specimens sent to Dr. Poiner were once again found to contain only saprophytic 26
fungi. The cause of death of the remaining 18. 8% of the larvae was
unknown. All hibernacula from which larvae were known to have
emerged contained none of the above indications of mortality factors.
A comparison of mortality for both years suggests that the
cold temperatures immediately following larval emergence in
1966 probably resulted in retarded deve10pment or death of many
of the larval parasites found within the dissected hibernacula. Similar
temperatures did not exist in 1967 and only two parasite pupae were recovered while mortality remained proportionately
constant.
Individual larvae which emerged from the tagged hibernacula were observed twice weekly during the entire spring feeding period in 1967; the original feeding site of each larva was recorded and all other larvae were removed from the entire limb.
Larval migration, pupation, mortality and feeding damage also were recorded at succeeding observations. If none of the clusters on the limb revealed the larva during later observations it was assumed to have left the tree. N June
hibernacula,
8 from
Emergence Migration Pupotion ~2
emergence
1967
(A! -
-- --- —- larval observation
Ho of Michigan
tricolorella May
Hart, 8 Date
soil
the
Acrobasis
in K: of
pupation ' S.
and
-Occurrence
[a 4. April
50-
30-
20-
40F- so—
snonp. MI pug peluesqo em 10 was 16d Figure migration
27 28
Observations of 38 emerged larvae indicated that larval migration occurred during most of the feeding period (Fig. 4). Migration was most evident from May 12 to 16 when 47% of the observed larvae moved.
This period corresponded to the beginning of bloom in which mature larvae moved from the base of the buds to spin loosely—constructed nests and to feed on the petals.
The average number of feeding sites occupied by each larva was
4. 23 i 0. 92. Most of the larvae were observed in four or five sites while two larvae moved only once. The most feeding damage to the buds was observed prior to full-bloom.
The absence of larvae on the limb was recorded between May
17 and 30. Mature larvae were observed to drop freely from the bud cluster. Their behavior did not indicate that they might drop to a lower branch and resume feeding. It is evident that they left the tree to pupate in the soil, as 48% of the larvae left the branch within the
4 day period between full bloom and petal fall. One larva remained until shuck-split, but none was found beyond this stage.
Before the emergence of larvae in 1967, each of 40 cherry trees was divided into four quadrants: south-upper, south-lower, north-upper and north-lower. Four replicates were tagged in each quadrant; each replicate contained five terminal bud clusters to be observed at twice weekly intervals during the feeding period.
Each bud cluster represented a single larval feeding site. Height of the sample clusters varied with the size of the tree, but lower samples were 3 to 4 ft. and upper samples were 5 to 10 ft. above the
30 1967
UPPER
UPPER in
LOWER
LOWER -
26
soum ~0an scum ~0an
TOTAL
23
intervals
Michigan at
------
—
I9 Hart,
~ \
L
\‘
I6
observed
“~ \
l
l2
‘9‘
replicates larvae
l
9 ’...... ‘
5
l cluster
’0’.
W-0~.~.~.--\:m\‘ /-.s‘...~‘~
OBSERVATION
I
"
/ bud
OF
l
-'
tricolorella
... I
(MAYIZ
DATE
L
26
-’
terminal
~u'QOO" -
1 ’.-.-.-.-.'.
25 Acrobasis
”-OOD---”
’.
of
“ tagged
2|
1-
/‘
‘.-.’.’ o-
'
J
I8
76-70..-.“
"I
12” containing
r’”
-Occurrence
’
5. I
l r
IPRIDM
9
susn so ussnnn
Figure quadrants
29
30
ground level. The presence or absence of larvae and larval
mortality were recorded on each sample date.
Larvae were observed in the tagged bud clusters on April 11
(Fig 5). The total larval pOpulation increased at each observation
during the following 5 weeks. The greatest number of larvae
recorded at one observation, 95, was present on May 9, 10 days
before full-bloom. This population increase was the result of the
presence of newly-emerged larvae and the presence of larvae
immigrating from distal points of the tree limb. The number of
larvae decreased steadily in the last 3 weeks of the feeding period.
Although this decrease was due in part to emigration from the sample
area, most of it was due to pupation as determined by the presence
of mature larvae.
Approximately two-thirds of the larvae recorded in three of
the four quadrants were present by April 18. The breakdown of
total larvae into each of the four quadrants showed that an unequal
distribution existed between them. At the time of emergence, the
south-lower and north-lower quadrants contained a higher population than did the south—upper and north-upper. This difference was evident through May 12. It was partially obliterated by varying rates of emigration after that date.
Larvae in the south lower quadrant emerged earlier and in
greater numbers than did those in the other quadrants. The
'p0pulation of this quadrant reached a peak sooner and completed
emigration seven days before the other quadrants. Southern l00— l l
o 9GP -—I967 g ---l966 ‘- o " 80- o .E .E2 70— C o o 2 60— .9.’ (D .2 0' 50— .0 D .0 U 4o” o o E 'o
‘5 o 20...
ot- O. IOh
\
Green Delayed ' Bud Bloom Post Shock tlp dormant separation bloom split Figure 6. -Occurrence of Acrobasis tricolorella larvae in damaged bud clusters collected at twice weekly intervals as related to bud development, Oceana County - 1966, 1967
31 32 exposure and reflection of heat from the ground could account for the more favorable environment in this part of the tree.
Infested bud clusters were picked at twice weekly intervals during each year of the study and dissected under a binocular microscope. The number of larvae present, the amount of bud damage and the stage of bud development were determined for each sample.
It is apparent from Fig 6 that the decrease in percent of larvae found in damaged bud cluster samples during 1966 agrees closely with that of those collected during 1967 when the comparison is made based on the stages of bud development observed in each year. The decrease in the number of larvae through the delayed dormant stage was, as discussed earlier, due to larval migration.
The bloom period is one of increased larval movement as indicated by the sharp decrease in the number of larvae present in the samples. This drop, from 64% to 19% in 1966 and from 52% to
19% in 1967, coincided with the occurrence of mature larvae and indicated that larvae had moved from the tree to the ground. It agreed closely with data recorded from several other experiments already discussed and correlated the time of maximum pupation with that of full-bloom. Following petal fall, larvae continued to drop to the ground at a greatly reduced rate for 7 to 10 days but the dropping was completed by shuck split.
Data from each of the three previous experiments were collected independently of each other. Observations of the small 33 number of larvae in the first experiment were given validity because they agreed with observations in the second which had a larger sample size. A comparison of Fig 4 and 5 to Fig 6 confirms that larval emergence from the hibernacula began during late green-tip,
April 7 to 11, and that all larvae had emerged by the 18th in 1967.
The increase of the population both in total larvae and within each quadrant after April 18 must be due to immigrating larvae in search of new feeding sites (Fig 5). This immigration to the terminal bud clusters was the result of a behavioral characteristic of _A_ tricolorella as it tends to move toward the periphery of the tree when selecting a new feeding site. If larval migration had been at random, immigration would have equalled emigration during this period. The trunks and major limbs of three trees known to contain larvae were handed with a heavy layer of Stickum Special in order to determine if larvae crawled down the trunk. No larvae were trapped, indicating that movement was not toward the trunk of the tree either during feeding or at the time of pupation.
In Fig 4, 5, and 6, larvae decreased steadily in number during the last 3 weeks of feeding and are known to have dropped to the ground in one experiment (Fig 8). This agreement in data indicates that most pupation occurs during the period of bloom but might continue at a reduced rate until shack-split.
Mortality of the spring larvae was determined for 15 larva collections made between April 11 and May 30, 1967 at Hart. It also was calculated from observations of an absolute population of CI Shelby I966
z 30'- § 25- 5 — O E 20- E ,5- 3 '1 3 IO- 0. 5": e I: e e m w
0 I I I I I I 5 8 l2 l4 I6 20 25 July
30 b Hort I967 : P
g 25- .q
o H E 20- ?, I5- 0 ‘- IO- " 0 n. 5 \ \ 0 l I I I I I i 23 26 3O 3 6 II I4 2| June .July
Figure 7. -Proportion of Acrobasis tricolorella larvae observed as dead in tart cherry samples collected at twice weekly intervals, Oceana County - 1966-1967 34
funnels
by
tunnels
2
adults
by
I
June
emerging
Adults.
Females
Caged
Trapped
and
-
I
30
-- --
larvae
l
26
mature
observation
l
of 22 l 23
I
Date
tricolorella
T
2|
20 observation
‘7’
\
of
I
l9
I
Acrobasis
/’
of
l
Date
l6
1966 -’
-
I
l4
’
~Trapping
8. June
May
I3
l4 Michigan IO IO I5 20 30 20 30 25 35
uauamdod ;a was led
Figure Hart, 35
35
38 emerged larvae and recorded from tagged bud clusters within
four tree quadrants.
Dead larvae were found in each sample between April 18 and
May 12, excluding May 5 (Fig 7). This was the period between the beginning of feeding by the majority of the larvae and the week prior to the onset of pupation. As the result of low nightly temperatures
during the last week in April, the percent of dead larvae rose
above 10% for the three samples collected between April 25 and May 2.
No mature larvae were observed to have died in the bud clusters.
Fig 8 indicates the spring mortality of a constant larva
population recorded on four dates between April 14 and May 5. On
April 14 and 18, two of the three larvae were assumed dead as they had emerged but were not present in the bud clusters. The hibernaculum of one of these larva was located on a dead limb. One
more larva was found dead in the bud clusters at this time. The
greatest single observation of mortality, four larvae or 11% of the population, was recorded on April 25. A total of eight spring larvae
or 21. 1% of the population diedduring the periods of emergence and
cold weather.
Dead larvae from both the samples and the observed population were examined for the presence of pathogenic bacteria and virus but
results were negative.
A comparison of Fig 7 and Fig 8 to Fig 6 shows that mortality
in both studies occurred before the bloom period, May 25 and May 19
respectively. In each case the greatest mortality at a single 36
observation was recorded after a period of below freezing nightly temperatures. While the relationship between temperature and mortality cannot be confirmed solely on the basis of these figures, the similar pattern in a constant population indicates that such a
relationship exists.
A relative mortality figure cannot be computed for the tagged bud cluster experiment as the population in the sample area varied at each observation. However, nine dead larva were removed from the northolower quadrant and three from each of the remaining quadrants.
During the preceding studies, several observations were made on behavior of the insect and on host phenology as it related to this behavior:
(1) Second- and third-instar larvae overwinter in dome-shaped hibernacula which completely cover them, from July, August or
September of one year to April of the following year (Plate I-l).
Hibernacula are usually located in the crotch of a fruit spur but may also be located under old bud scales, loose pieces of bark, or in bark depressions. The hibernaculum consists of two separate layers of silk—like material. The inner layer is soft and white. The outer contains foreign matter such as sand or minute pieces of bark. The color of the latter layer may range from beige to brown or black.
Hibernaculum size vary between 1 and 4 mm. A few strands of white webbing may be stretched across the fork of the twig in which the hibernaculum is located. 37
(2) The occurrence of emergence was determined by the presence of a hole formed in the hibernaculum by the overwintering larva which then left to feed in the cherry buds. The hibernacula were not consumed by the larvae nor did any of the larvae return after emergence.
(3) At emergence from the hibernaculum the larva crawled along the twig to a nearby cluster of buds where it began to construct a nest formed of strands of webbing between two buds or one bud and a twig. The larva burrowed into the lower one -third of a blossom bud. It consumed the developing flower parts from within, leaving only the outer scales. Entrance holes eaten in the buds were usually plugged with webbing and frass. Superficial damage in the form of a small hole in the bud scale was occasionally found on a leaf bud but the leaf buds were not entered by the larva.
(4) All buds in an infested cluster were held together by strands of webbing. The larva formed a tube—like nest of tightly woven webbing at the base of the buds in the center of the cluster. At the time of full-bloom, the larva often moved to a new cluster (Plate I-4).
Webbing and a tubular nest were usually formed again, but a larva was sometimes observed to feed on many of the blossoms by entering from the top without first making a nest. In either case, webbing was found lightly holding the petals together, and large quantities of frass were present. The larva fed primarily on the flower parts and occasionally on the petals. 38
larval development. -
To determine the number of instars of_A_:_ tricolorella larvae,
the head capsules of 570 field—collected larvae were preserved in a
mixture of kerosene, ethyl alcohol and acetic acid and later tranferred
to 80% ethyl alcohol; these were measured at the widest point of the
vertex with an optical micrometer on a binocular microscope. No
larvae which died before preservation were measured.
Measurements of head capsule size indicated the presence of
five larval instars. Cast-off head capsules of all instars were found
indicating the moult to a new instar.
The maximum, minimum and mean head capsule widths in
millimeters were as follows:
Larval instar Minimum Maximum Mean
1 .16 .24 .20_-_|_- .020
2 .28 .36 .32-_+_.024
3 .40 .62 .52: .045
4 .64 1.02 .79 _-I_-_ .064
5 1.06 1.48 1.28 i .108
These data agree with those obtained by Dever (1953) on the destructive prune worm. The determination of instar development by measuring the head capsule width of field collected larvae is of value in determining the seasonal development of larvae under natural
conditions and is a useful aid in the identification of unknown specimens. 39 feedinisites and pogulation estimate of emerging larvae. -
In the spring of 1967, dimensions of 11 cherry trees in the
Hart orchard were measured, and the number of bud clusters on each tree was recorded. A bud cluster consisted of a group of two or more buds of which one was a flower bud. Selected trees were with- out visible limb damage and varied in height between the extremes found in this orchard.
A multiple linear regression analysis (Steele and Torrie 1960) was computed for effect of all factors together and individually on bud clusters, the dependent variable. Trunk diameter, one foot above the ground, crown height, crown diameter, tree height and crown surface area were the independent variables. When all factors were analyzed together, the over-all multiple regression r equalled . 9632; thus,
(. 9632)2 or 92. 77% of the variation in bud clusters could be accounted for by the five measured parameters.
The effect of each factor on bud clusters with the others held constant was determined with a partial regression analysis. The least significant factor in each regression was dropped and the remaining factors recalculated. Trunk diameter and tree height had a significant effect on bud clusters at the . 05 level. The single greatest factor was trunk diameter which had a correlation coefficient r = . 9583, significant at the . 0005 level (Fig 9 and Table 4).
This one variable accounted for (. 9583)2 or 91. 83% of the variation in the number of bud clusters between trees. A change of one inch in the trunk diameter corresponded to a change of 381. 3 bud clusters. Table 4. ~Analysis of Variance for linear regression
55 DF MS F Sig.
Regression 5964548. 049 1 5964548. 049 101. 1941 . 0005
Error 530474. 859 9 58941. 651
Total 6495022. 909 10
Table 5. -Simple correlation results between trunk diameter, tree height, crown diameter, height and area, and number of bud clusters of tart cherry trees, Hart, Michigan-1967
Variablesa Dia Cluster Tr Ht Cr Dia Cr Ht Cr Area 1 2 3 4 5 6
1 Dia -
2 Cluster .9583
3 Tr Ht . 8701 . 8821
4 Cr Dia . 7828 . 6989 . 7515
5 Cr Ht . 6906 . 6588 . 9070 . 6478
6 Cr Area . 7789 . 7004 . 8631 . 9343 . 8477
aVariables: Dia = Trunk Diameter, Cluster = Number of Bud Clusters, Tr Ht = Tree Height, Cr Dia = Crown Diameter, Cr Ht = Crown Height, Cr Area = Crown Area
Simple correlation coefficients between all factors are given in
Table 5.
A bud cluster is the normal spring feeding site of the third- to
fifth-instar larvae. During this feeding period, an average of 4. 23 f 40 ll J X _
of l I0 38I.965l +
diameter l
trunk 9
the
and -980.4337
inches 8 r=.9583 9=
tree J
in
per l 7
clusters
bud
1966
diameter
of
- 6 l
number
Trunk
Michigan
the 5
Hart,
between
cherry 4
tart
—Re1ation
in
9.
tree
'- l
l -
3
the
o Figure 8 0 IO ID
N l000 3000 eleisnp pnq lo JeqwnN
41 42
. 9196 bud clusters are attacked by one larva. The estimated number of bud clusters in the research block, as determined from the trunk diameter of 40 trees was 54, 910 (Fig 9). This is equivalent to
137, 270 bud clusters per acre of 100 trees. The maximum density estimate of a theoretical random larvae population without intraspec‘ific competition was 32, 450 per acre of trees.
An estimate was made of the emerging larva population density by comparing the 63 larvae present on June 21 in the 3, 200 tagged clusters with the total feeding sites per acre. June 21 was selected because emergence from the hibernacula was completed but general migration had not yet begun. This population estimate was 2, 701 per acre.
Another completely independent estimate was made by removing branches from an unsprayed section of the research orchard, bringing them to an unheated building and counting the larvae at daily intervals as they emerged. Eighty-three larvae were removed and 2, 511 feeding sites were counted. By this method, 4, 537 larvae per acre were estimated to be present. This procedure overestimated the population however as limbs were removed from the lower half of the trees which contained a higher larva population (Fig 5). Thus the estimate of
2, 701 larvae represents the more accurate figure obtained.
Pupa stage. -
The incipience of the pupa stage was determined from daily observations of mature larvae that were trapped as they dropped to 43 the ground. Duration of pupation was determined as adults were trapped upon emergence from the ground. One funnel trap was situated under the periphery of both the north and south halves of 38 trees; 28 larvae were collected between May 16 and 30, 1967 (Fig 8).
No difference occurred in the number of larvae trapped betwaen halves of the tree although a highly significant difference occurred between trees.
A comparison of the dates when larvae and adults were removed from funnel traps (Fig 8) indicates that the interval between the dropping of the first larva and emergence of the first adult was 28 days. The average interval between the collection of all mature larvae and all adults found in the traps was also 28 days.
The pupation period was recorded from observations both of cocoon formation by field-collected larvae and of adult emergence in cloth cages located in the research block. This procedure was modified in 1967 by placing individual pupae in shell vials under 1 inch of sand and by recording the date each adult emerged.
In 1966, 30 cocoons were formed by larvae between May 27 and 30, corresponding to the bloom period of flower development.
Each day some of the cocoons were opened to reveal the formation of a stationary prepupa stage; which lasted 3 to 5 days, before the obtect pupa was formed. Sixteen of the pupae measured 72. 87 f
. 04 mm (Plate I-6). Emergence of 15 adults occurred 28 to 35 days after pupation. 45
The incipience of pupation as determined in field cages and funnel traps coincided with a reduction in the number of larvae present in the bud clusters during the period between bloom and petal-fall to show that most pupa formation occurred at this time and continued at a reduced rate through shuck-split. This pupation period agrees with that determined in the feeding-larva study.
There was an extremely close correlation between cage and funnel trap experiments indicating that although a wide range of 19 to 31 days in pupa duration existed, the average number of days was 28 to 29. If an adjustment for the pre'pupa stage is made, the actual length of pupation is reduced to 23 to 25 days.
The mature larvae dropped to the ground and pupated in the soil. They formed cocoons containing sand or dirt and occasionally debris (Plate II-7). The amount of time required for a larva on the ground to find a suitable pupation site and to spin a cocoon could not be determined but the agreement bemeen experiments indicates that this was not an important factor in determining the duration of the pupa stage.
An estimation of pupa density was made by dividing the total of 28 larvae recorded in 76 funnel traps by the total funnel trap area. One larva was trapped for each 14. 59 ft2 of trap area.
This is the equivalent of 6. 86 larvae per 100 ftz of trap area and is the basis for estimating the population at 3, 684 pupae per acre of crown cover. 46
Adult moth stage. —
Three types of ovipositional cages: wire sleeves over tree branches, cloth cages on the ground in the orchard and sand-filled pots containing foliage in a controlled environment chamber were evaluated to determine which was the most suitable for fecundity experiments.
In two separate experiments female moths in glass cages produced the greatest number of eggs. Fifteen moths of undetermined sex ovi- posited 100 eggs which were observed 6 to 8 days after adult emergence.
Mean number of days for occlusion was eight (4-11), and 97% of the eggs hatched. Four virgin females caged with one to three males each oviposited 54. 75 _-I_-_ 10. 64 (45-69) eggs, 4. 2 _-l_-_ . 43 (4-6) days after being caged. The greatest number of eggs of each female hatched in 7 to 9 days. The range of hatching was 4 to 12 days and the percent of eggs
'which hatched was 94. 5 i . 45.
No eggs were laid by moths placed in wire sleeve cages and only
12 eggs were collected from a total of 10 females in cloth cages. Five to 15 moths were placed in each of the field cages. Moths in sleeve cages usually died in 2 or 3 days as compared with those in cloth cages which lived approximately 2 weeks. The difference may have been due to the restricted space and reduced light in the former cages.
Females recovered from a black light trap and virgin moths were placed in 90% ethyl alcohol and dissected under a binocular microscope. A mean of 138. 6 :16 .68 (116-158) eggs was counted in the ovaries of
10 virgin females. This represented egg-laying capacity. In the orchard probably not all of the eggs are expelled. Ten females recovered from 47 the black light still contained a mean of 46. 63 :19. 04 (21-79) eggs per moth. Thus an average of 90 eggs per female is deposited in the field.
This rate of oviposition compared more favorably with females in glass cages actually laying at a rate of 54. 75 eggs than did the mean number of eggs in virgin females.
A duration of 12 to 14 days existed between the mating of insects in glass globes and the emergence of the larvae. This compared favorably with estimates from field collected data. Seventeen days elapsed between trapping of the first adult with the black light trap and the first observations of the larvae in the fruit. This period was 9 days as recorded by the funnel trap.
Periods of moth flight were determined through the use of black light and funnel traps. Black light traps located in unsprayed tart cherry blocks were operated nightly from June to September. Mechanical failure of the black light terminated this phase of the study at Lake
Leelanau in August of 1966 and at Hart and Shelby in August of 1967.
The collections each night were evaluated for the nurriber of _A. 551: colorella moths present. In 1967 sex of the maths caught at Hart also was determined.
There was agreement in 1966 among all three experimental orchards in which black light traps were used concerning relative incipience, peak and termination of emergence (Fig. 10, 11, and 12).
The first flight of moths was observed at Shelby on June 12, at Acme on
June 14 and at Lake Leelanau on June 17. These emergences occurred 48
18 days after full bloom at Shelby and Acme but an uneven bud develop- ment prevented determination of the full bloom at Lake Leelanau.
Incipience of adult emergence occurred in 1967 on June 6 at Hart,
June 8 at Shelby and June 13 at Acme (Fig. 13, 14, and 15). These dates were 18 to 19 days after full bloom at Hart and 20 days after full bloom at Shelby. The bloom period was not determined at Acme. The largest catch in both Oceana County orchards was taken on June 23.
Duration of emergence was 27 days at Hart, 22 days at Shelby and 29 days at Acme.
These two years of data indicated that moths began flight 18 to 20 days after full bloom and were trapped in the orchard for another 22 to
27 days.
Hourly collections were made on four consecutive nights during the period of adult moth flight. Moths were attracted to the black light beginning at dusk. They increased in number and reached a peak of activity between 1:30 and 3:30 AM on 3 of the 4 nights (Table 6). There was a sharp reduction in the number of moths trapped after this hour.
This may have been related to the nightly increase in humidity until about 3:30 AM and the increased amount of daylight after 4:30 AM.
There was also a significant difference in the number of moths recorded for each date.
The proportion of females to males also was calculated on a daily basis in 1967 (Fig. 13). The mean ratio was 0. 307 indicating that more males were trapped than females.
Table 6. -Hour1y flight patterns of the adult Acrobasis tricolorella as determined by trapping with black light at Acme Mchiga-l966
PM AM 8:30 9:30 10:30 11:30 12:30 1:30 2:30 3:30 4:30 Total to to to to to to to to to 9:30 10:30 11:30 12:30 1:30 2:30 3:30 4:30 8:30
6/23 0 22 29 29 41 71 115 26 4 337
6/24 2 26 so 27 29 71 9o 19 8 332
6/25 1 10 10 16 14 28 25 23 2 129
6/26 0 5 5 74 34 18 5 l 2 144
Total 3 63 94 146 l 18 188 235 69 1 6 932
Mean . 75 15. 75 23. 50 36. 50 29. 50 47. 00 58. 75 17. 25 4. 00
Within-tree variation of emergence was determined by the construction of grids consisting of 10 traps each under three selected trees. ’I‘wo traps in a north-south line were placed adjacent to the trunk, but lack of area prevented the addition of traps in an east-west grid. Four traps, one at each compass point, were placed under the inside perimeter of the crown and four were placed under the outside perimeter. Due to the low density of the population variation between trees was not determined.
As shown in Table 7, significant difference existed between the total of 16 adults trapped in the north-south grids as compared to two in the east-west grids. As larvae were assumed to pupate under the half of the tree in which they fed, it was apparent that those parts of the trees which were subjected to a lower light intensity and greater
49 Table 7. -Number of Acrobasis tricolorella adults which emerged from three funnel trap grids, Hart Michigan-1967
North South East West Total
Adjacent to the tree trunk 3 l _a _a 4
Under crown perimeter 0 5 1 0 6
Outside of crown perimeter 5 2 0 l 8
Total 8 8 1 l
ano traps in this area
physical interference from limb movement of adjacent trees also contained a lower infestation. This was possible since the trees were planted in rows which ran in an east-west direction. Although no significant difference existed between inner, middle and outer traps of the grid, the largest number of moths was removed from the outside perimeter of the tree. Thus when larvae drop to pupate they may be blown away from the area immediately under crown cover. The within- tree variation recorded by the grid experiment indicated that a limited number of funnel traps could most efficiently be used by distributing them one per tree at the periphery in either the north or south halves in as large a sample of trees as possible.
In addition to the above-mentioned 30 traps, two funnel traps were placed under the periphery in the north and south halves of each of 20 trees and inverted to trap adults as they emerged from the ground. Ten additional traps, two per tree, were moved randomly at weekly intervals to determine if the presence of the trap created an artificial environment. 50 51
Adult emergence as determined from funnel traps is expressed as percent of the population that emerged per sample date (Fig. 8).
Duration of emergence for 24 adults collected beginning June 14 and
continuing to June 26 corresponded closely to that observed in the black
light trap. In contrast to the large number of males recorded in the black light traps, both sexes were recorded with equal frequency in these emergence traps. The funnel trap measures the absolute density of adult emergence; therefore, it substantiates the duration of emer-
gence as recorded by the black light, but it does not confirm the numbers nor the emergence pattern derived from the light trap. Unlike the emergence trap, the light trap's use for density estimates is influ- enced by variations in weather, insect mating behavior and trap location.
The absolute population density of adults was estimated from the
12 moths recorded in 40 funnel traps. One adult was trapped per
17. 91 ft2 of trap area. This was the equivalent of 5. 58 adults trapped per 100 ft2 of trap area. The population density computed per acre of
crown cover assuming random distribution under the tree was 3, 000 moths. Although the distribution was not equal under all parts of the tree, the estimate was not corrected for this factor.
The difference of 684 pupae which existed between the mature larvae estimate of 3, 684 and the adult estimate of 3, 000 can be att ributed to pupa mortality and to sampling error. 500y ¢
475 r
450 -
425' 4oo~
37s- saor
325-
night 300L
per 275+
250-
moths 225 -
of
200 T
I75?-
Number I5O " l25 P IOO '
75- 50¢
25” 0 J I I 1 1 f ré u mu I 7 l2 I7 22 27 2 7 I2 IT 22 27 I 6 ll l6 2| 26 3' JUNE ‘ . JULY AUGUST DATE OF CAPTURE Figure 10. -Seasonal adult Acrobasis tricolorella flight as determined by trapping with black light Shelby, Michigan - 1966
52 29 with
22
. trapping by
I5
1
8 determined as
I
AUGUST flight
Is
f CAPTURE tricolorella OF
JULY
I
4 1966 DATE - Acrobasis
T
27 adult
Michigan
r
20 Acme, -Seasonal
11. light
I3‘
JUNE
O O
0 208’ Figure 6 «now 10 Jaqumu black 53
0
black
with
I
AUGUST
trapping
by
I8
determined as
flight
CAPTURE
I
4
OF
JULY
DATE
tricolorella
1966
-
27
Acrobasis
Michigan adult
1 20
-Seasonal
Leelanau,
12.
F
Lake
‘
-
-
.
-
"
*- ~
"
-
"
'
h I3
JUNE
C
‘
light
Figure
IO
l2
,0
24'-
42 48
36
54
60
66 72 18 04 lubgu Jed sqiow io JOQUJHN
54 with
trapping
by
Total
Females
-
-
July
l
-
determined
30I
as
flight
capture \’
25
--ll== of
I
l i...‘
20
Date
tricolorella
1967
-
Acrobasis
Michigan
Hart,
-Seasonal
6
13.
rLl I I l light
June
O o O 4 .9 8 8 c o '0 N IoL
I50
Figure iubgu Jad sulow lo quwnN black
55
I 20
black I
I5
with IO trapping
by 5
determined
July I
as
1
301 capture flight
of
l 25
Date
tricolorella.
UN
I [ 20 196T
' -
Acrobasis
I I5 adult
Michigan
I I0 Shelby,
-Seasonal 8 14. South
- l I 1 l
June
o o O 4 0 light an 8 e N Figure
I20-
I40- I00 iufigu .Iad squw io .IaqumN
56 by I5 determined 5 as AUGUST I flight 25 1967 - Capture tricolorella of I5 Michigan
Date
Acrobasis 5 Acme, I
JULY adult light
25
black
-Seasonal
with
I I5 15.
JUNE 0
I2
28- 32L
20- Iubgu .Iad 3mm: 40 JaquInN Figure trapping
57 57
Secgnd generation stage. -
Observations were made on a second generation of A. tricolorella which infested cherry orchards located at Acme, Shelby and Hart in 1966. Three hundred nineteen cherries placed in a field cage yielded l
130 hibernacula on tree branches and 21 pupa cocoons located in sand.
Thirty—five mature larvae from another orchard produced 33 cocoons; two larvae died. The first pupation was observed 20 days after the incipience of fruit infestation. The presence of mature larvae in the fruit and the formation of cocoons were the first indication of the occurrence of a split brood.
The pupae did not overwinter but began emerging in the field cages between August 1 and 9, 16 to 24 days after cocoon formation.
Black light traps were maintained to record the flight of second generation moths. Adults were initially trapped in the three orchards on July 27 and 28, 1966, seven to 10 days after the beginning of harvest.
The second brood was much smaller in number in the first representing
5. 05% of total adult population at Shelby and 8. 33% of that recorded at Acme. Duration of flight varied from 27 to 36 days. In 1967 only one black light was operating during the flight period of second brood moths.
One moth was trapped on August 15 at Acme. It was not determined if this result indicated a variation in the size of the second brood as compared with 1966 or a change in the trapping efficiency of the black light.
Observations of second brood larvae showed that they form a nest on the under side of cherry leaves (Plate I-5). One hundred and seventy- 58 five leaf nests, removed from the Shelby orchard between August 20 and
September 4, yielded 20 first and second instar larvae. In addition, the majority of larvae reared from second brood eggs fed and constructed nests upon leaves placed with them in petrie dishes.
Second brood larvae fed primarily on the lower epidermis and mesophyll of the leaf. Parts of the upper epidermis were also eaten to give the leaf a skeletonized appearance. Those parts of the upper epidermis above the. feeding area turned brown; thus the larval damage was easily discernible. Occasionally, feeding damage was observed on the midrib. Caged larvae were also observed to burrow directly into the woody portion of a twig. Webbing and a small pile of frass were present at the opening.
Infested leaves were removed from trees and dissected with the aid of a binocular microscope. The larval nests were on the under- side of the leaves adjacent to the midrib and consisted of two protective coverings. The outer covering was a loose canopy of shiny silk extending over the lower epidermis which was used as a feeding area. The ends of this canopy were attached to the midrib and the leaf. As the feeding area increased, the strands were filled with bits of frass. The larva, as it grew, formed a second covering under the first. This was a tightly woven cylinder immediately adjacent to the midrib. This tubular nest consisted of dulllsilk strands that formed a smooth interior surface, protected externally by bits of frass. The cylinder, 1mm wide and l to
10 mm long, was just large enough to contain the larva. Its length increased with the duration of the larva on the leaf. 59
Second generation larvae caused no economic damage to the fruit crop as they appeared several weeks after harvest. Although they fed primarily on the leaves, they were occasionally found feeding on both fruit in the laboratory and on unpicked fruit in the field. In orchards where the fruit is not harvested, it is possible that more cherries would be infested. The absence of any post harvest insecticide application may greatly increase the following year's infestation. JJ As indicated by the reduced number of larvae observed in leaf nests gathered during the first week of September, it may be concluded that hibernacula are probably formed by second brood larvae during the latter part of August.
Timing According to Stages of Bud Develogment. [-
The development of host and parasite can often be correlated as both often require the same environmental conditions for development.
The various stages of bud development in tart cherries can be used to determine the feeding habits of the insect. Determination of stages is made from the appearance of the tree as a whole since environmental variations may cause buds on one area of the tree to be further or less advanced than those on the remainder of the tree. Stages are dated according to their occurrence in the Oceana County, 1966-67.
Plate 1. - Stages in the life history of Acrobasis tricolorella showing: (1) hibernaculum in crotch of cherry twig (2) fourth instar larva in opening buds (3) feeding damage to buds (4.) fifth instar larva at full bloom stage (5) leaf nest of second generation larva (6) pupae.
6O v . ’ ".y.' . . _ .- "a _ “a . ..|
® ‘ “ . \IV .. 4. ' . 6", J: \I!*. . ‘ t‘” (‘ . '
.,
Plate II. -Stages in the life history of Acrobasis tricolorella showing: (7) cocoon (8) adult (9) egg (10) fourth and fifth instar larvae (11) injury to fruit by second instar larva (12) cherry fruit Split open showing feeding of second instar larva (l3) injury to fruit by third instar larva 61 62
Green-Tip
Early - month of March. Larvae are in hibernacula. Bud scales
have separated exposing the underlying green tissue.
The bud is expanding slightly but remains firm to the
touch. (Plate III-l)
Late - Second and third weeks of April. Larvae emerge from
hibernacula. The buds are slightly pliable due to the
presence of air within. The amount of green tissue
present has increased and continues to protect the leaf
or flower parts within. (Plate III—2)
Delayed- dormant - Begins fourth week of April. Larvae feed in
buds. One quarter to one half inch of the leaf tip is
exposed. In flower buds, green tissue is approximately
twice the height of the bud scales'. A slight crease may
be visible across the top of the bud. (Plate III-3)
Bud-Separation - third week of May. Larvae continue feeding in
buds. Flower buds have opened to expose individual
blossoms. Blossoms begin to swell but remain covered
with green scales. More than l/2-inch of the leaves is
exposed. (Plate III-5)
Bloom - fourth week of May. Larvae move to new bud clusters
and may pupate as petals fall. Green tissue has
separated to expose white petals. Petals expand and
open. The entire leaf is exposed. (Plate III-4) 63
Shuck-split - first week in June. All larvae have pupated. First
adult emergence occurs 3 to 7 days after this stage.
Receptacle parts protecting ovule turn brown and fall
away. (Plate 111- 6)
anemical Control. -
Spring applications. -
Insecticides in the Shelby orchard were blower applied. The amount of spray applied was halved, compared to a dilute spray of 300 gallons per acre. Half of each tree was sprayed. The side of the tree receiving thorough coverage was called the direct side and the remaining side was the indirect side. The experiment was replicated four times with a replication consisting of 10 grees for each treatment. Chemicals were applied May 3, 1966. The treatments were evaluated on May 16 and 19, 1966.by a field collection of 25 damaged bud clusters per replicate. Clusters were stored in polyethylene bags and later examined under a binocular microscope in the laboratory for the presence of alive and dead larva.
As shown in Table 8, Azodrin (dimethyl phosphate ester with gigs
3 - hydroxy- N-methylcrotonamide) and parathion gave better control than any of the other treatments. At the time of application the air temperature was 45 F. It was cold throughout the following 24 hrs and the fumigant action of parathion was minimized. However, parathion 44 ‘- \ o 3' .3 \. is r ) h l 1' a c4 '0 .1 .I l
a-'
[I 1.... C ‘ o Iv o - . D
. I’l'
D fi
Plate III. -Stages of bud develOpment in tart cherry showing: (1) early greentip (2) late greentip (3) delayed dorment (4) full bloom (5) bud separation (6) shuck Split
64 65 also is effective as a contact spray. Imidan (O, O - dimethyl S- phthalimidomethyl phosphorodithioate) and azinphosmethyl were not effective in this experiment.
The spraying of alternate rows in the orchard in an attempt to reduce costs gave significantly less control (Table 8) than did spraying every row. Many larvae in the buds on the side of the tree not receiving a direct spray were able to survive and continue feeding.
This was determined by the selection of infested bud clusters from directly and indirectly sprayed sides of each tree; pairing them and calculating differences in larval mortality for each treatment.
The Wilcoxin non-parametric test for paired comparisons
(Siegal 1956) which measures the magnitude as well as the direction of any observed differences showed p(t < 11), significant at the . 05 level.
This indicates that both sides of the tree must be sprayed thoroughly for best control.
Some growers spray on a weekly basis alternating sprayed and unsprayed rows. Since precise timing is important for maximum effectiveness, this method is not recommended.
The delayed dormant treatments at Lake Leelanau orchard were gun-applied dilute sprays with four replicates per treatment and six trees per replicate. Both sides of the trees were sprayed. Spray application was made on May 24 and the treatments were evaluated
May 29—31. Damaged bud clusters were collected from each replicate, placed in polyethylene bags and examined in the laboratory for the presence of dead larvae. As shown in Table 8, Azodrin and parathion Table 8. -Effect of various insecticides applied to tart cherry in the delayed dormant stage on Acrobasis tricolorella third- to fifth-instar larvae, Shelby and Lake Leelanau, Michigan-1966
Mean % mortality:
Treatment Dosagea Indirect Direct
_S_lle_l_b_y _Sh_9_1_by Lake Leelanau
Azinphosmethyl 0. 5 37. 5(40) 45. 9(37) 85. 7(28) ZEC
Imidan 3EC 0. 75 23. 7(59) 42. 6(47) 29. 8(17)
Azodrin 5EC 0. 5 64. 6(48) 82. 9(41) 100. (ll)
Parathion SEC 0. 5 68. 4(38) 85. 7(35) 100. (12)
Endosulfan ZEC 1. 0 - — 92. 0(25)
Control - 9. 5(42) 9. 1(44) 0 (ll)
apounds active ingredients per 100 gal water
l”Indirect = side of tree not receiving insecticide; direct = side of tree receiving insicticide; both sides of the tree were sprayed at Lake Leelanau; no. in parenthesis 1' no. of larvae observed
gave outstanding control of the larvae; azinphosmethyl, Imidan and endosulfan gave commercial control of this pest. Low temperatures delayed larval emergence until May 7 and insecticides were applied
17 days later. The extremely cold weather, which froze 70% of the
flower pistils, continued throughout the evaluation date and may have delayed feeding and nest building and made the larvae more susceptible to the action of the insecticides than they would have been at warmer temperature 8 . 66 67
Azodrin and parathion were the most effective insecticides evaluated in both spring experiments based on percent mortality.
Azinphosmethyl performed more effectively at Lake Leelanau than at
Shelby. Promising results were obtained with endosulfan and Imidan.
Summer applications . —
The preharvest treatments at Lake Leelanau orchard were applied with a hydraulic gun using dilute sprays. Four replications per treat- ment were employed, a replication consisting of six trees. The materials were applied June 27 and July 10, 1966 and the plots were evaluated on July 14 and 15, 1966. Cherries were selected at random within each replicate and the presence or absence of larval damage was recorded for each.
Effective control of the larva was achieved with a single application of all insecticides employed (Table 9). The first application, timed to coincide with peak adult emergence was probably effective against both eggs and adults since adult activity began June 17. The second app- lication applied 10 days after larvae were observed in the fruit did not increase control over that obtained from a single application. Since larvae were already in the fruit, they may not have been affected by the second application of insecticides.
Chemical treatments in the Hart orchard on Tyler Road were blower applied, 2X concentration based on 300 gallons of dilute spray per acre. There were three replications per treatment, 15 trees per replicate. The dates of application were June 27 and July 10 and those 68 of evaluation, July 14 and 15. Evaluations were made by recording all cherries in each replication as infested or non-infested. Results of chemical treatments at Hart showed that Azinphosmethyl and parathion gave satisfactory control (Table 10). The remaining treatments did not give satisfactory control.
Ultra low volume methods were employed to apply the summer treatments in the Hart orchard located on Old U. S. 31. Each block consisted of approximately 100 trees. Evaluations were made from the center trees of each block. The insecticides were applied on June 10,
June 22 and July 8, 1966 and the plots were evaluated on July 19, 1966.
All insecticides were highly effective (Table 11). The first spray,
June 10, was applied 2 days before moth emergence so that its residue protected the foliage until the second application. A third application was made 3 days after the larvae were observed in the cherries so that this application may have had little effect in controlling the pest.
The 23% infestation of the control in this experiment is the highest recorded in any of the orchards. The difference between this percentage and those recorded in the treatrnents emphasizes the effect of proper timing in control of the adult moth.
Treatments in the Hart orchard in 1967 were applied with a hydraulic gun using a dilute spray of 2 gal per tree. Ten trees per treatment were employed with two replications per tree. The materials were applied on June 14 and June 30, 1967, and the treatments were evaluated on July 11, 1967. Evaluations were made from 100 cherries Table 9. -Effect of various insecticides as preharvest applications to tart cherries on Acrobasis tricolorella larvae - Lake Leelanau - Michigan - 1966
One application _ Two applications Total Total a cherries Percent cherries Percent Treatment Dosage examined infested examined infested
Endosulfan 2EC l. 0 3792 0. 5 4480 O. 3 Parathion SEC 0. 5 3697 O. 6 3088 0. 4 Azodrin SEC 0. 5 2719 0. 3 3239 0. 2 Imidan 50 WP 0. 75 3746 0. 2 2277 0. 3 Azinphosmethyl 0. 5 2778 0. 1 4184 O. 2 2EC Carbaryl l. 0 1374 0. 7 3036 0. 7 5 Flowable Control - . 4147 7. 4 3498 4. 3
apounds active ingredients per 100 gallons water
Table 10. Effect of various insecticides as preharvest applications to tart cherries on Acrobasis tricolorella larvae - Hart, Michigan - 1966
a Total cherries Percent Treatment Do sage examined infested
Lead Arsenate 0. 5 + 0. 5 1690 4. 3 Parathion 8EC Azinphosmethyl 25% WP 0. 25 2981 l. 7 Lead Arsenate 0. 5 2147 3. 3 Carbaryl 5 Flowable l. 75 2163 3. 6 Perthane 4EC 2. 0 ' 2102 2. 5 Parathion 8EC 0. 5 2197 l. 4
Control - 3431 9. 9
apounds active ingredients per 100 gallons water 69 Table 11. -Effect of various ultra low volume-applied insecticides as preharvest applications to tart cherries on Acrobasis tricolorella larvae Hart, Michigan - 1966
Treatment Dosagea Total cherries Percent examined infested
Thiocron 2. SEC 1 2000 l. 5
Azinphosmethyl 2ULV l 2013 . 5
Azodrin SEC 1 2013 . 0
RP 11974 3EC 2 2035 . 8
Control - 2093 23. 9
a'pounds active ingredient per acre bS ((6-chloro-2-oxo-3-benzoxazolinyl) methyl) 0, O-diethyl phosphorodithioate
Table 12. -Effect of various insecticides as preharvest applications to tart cherries on Acrobasis tricolorella larvae Hart, Michigan - 1967
Treatment Dosagea Total cherries Percent examined infested
GS 13005 40 E 0. 5 2000 1. 6
Nia 10242 50 WP 0. 5 2000 . 9
Azodrin 3. 2EC O. 4 2000 . 3
Azinphosmethyl 0. 5 2000 1. 6
Control - 2000 10. 9
apounds active ingredient per 100 gallons
70 71 which we re selected at random from each replicate and recorded as being infested or non-infested; Azodrin and Nia 10242 (2, ~3-dihydro-2,
2—dimethyl—7nbenzofuranyl methylcarbamate) gave outstanding control
(Table 12).
Timing of spray application to within 1 week of adult emergence as determined by black light was effective in reducing the insect population thus confirming the results of 1966. SUMMAR Y
Acrobasis tricolorella Grote is an economic pest of Michigan
tart cherry orchards since its presence in the fruit constitutes adulteration under a 1929 Michigan Act. This study, conducted during 1966 and 1967 showed that emergence of first generation moths began 19 to 20 days after the full bloom stage of flower develop- ment and continued for another 22 to 27 days. Both sexes emerged with equal frequency. The p0pu1ation in 1967 was 3000 adults per acre of crown cover. Females were found to contain an average of
138 eggs of which 90 were oviposited on protected areas of fruit spurs and on the underside of leaves. Eggs were laid 4 to 6 days after adult emergence and hatched in 7 to 9 days.
Immature larvae entered near the stem of the cherries and burrowed irregularily toward the pits. They continued to feed around the pits and formed small pockets in the tissues of the cherries;
12. 12% of the cherries were infested. There was no significant difference in the number of larvae between all 4 areas of the tree.
The majority of the larvae fed in the ripening cherries for 11 to 14 days before leaving to form hibernacula in the crotches of the fruit spurs. The two periods of greatest summer mortality were at the time of larval migration: to feed in the cherries and to form hiber- nacula. Overwintering larvae were in the second and third instars.
Some larvae did not form hibernacula but continued to feed in the cherries until they were mature. These larvae dropped to the ground to pupate and initiated a second generation. The moth population was
72 73 5% of the size of the first generation in 1966 and less than 1% of the first generation in 1967. The larvae from eggs laid by these moths fed upon leaves in nests constructed adjacent to the leaf midrib.
Larvae formed hibernacula which could not be distinguished from those formed by first generation larvae. This generation is important since it occurs in the orchard after harvest and contributes to the following year's insect population.
The hibernacula consisted of two separate layers of silk which completely enveloped the larvae and varied in size between 1 and 4 mm.
Larval emergence in the spring coincided with the late green- tip stage of bud development. The winter mortality was 44. 6% in
1966 and 48. 1% in 1967. Parasitism and dislodged hibernacula contributed to winter mortality. Two parasites belonging to the
Families Eupelimidae and Pteromalidae were identified.
At emergence the larvae crawled along the twigs to nearby bud clusters where they constructed nests and began to consume the interior portions of the buds. Spring larvae fed in an average of 4. 2 clusters and consumed up to 75% of each during the bloom period.
The largest number of larvae was present in the lower half of the trees. The majority of larvae dropped to the ground to pupate during full-bloom and continued dropping at a reduced rate through shuck- split. The greatest mortality recorded on one date was 21% and was probably caused by low temperatures. Measurements of larval head capsules indicated the presence of 5 instars. 74 The fifth instar larvae spun cocoons and formed a prepupa
stage lasting 3 to 5 days before the onset of pupation. Pupation then occurred in the soil and lasted 23 to 25 days.
Chemical applications were timed to coincide with emergence of both the spring larvae and the adult moth. Emergence was determined by observations of spring larvae feeding in bud clusters and by trapping of the moth with black light. Chemicals applied in the spring gave partial control of A. tricolorella larvae. It was determined that
both sides of the trees must be sprayed for maximum effectiveness.
Several chemicals gave excellent control when the first of two applications coincided with the trapping of the first moth and the
second application followed in 11 to 14 days. LITERATURE CITED
Dever, D. A. 1953. An analysis and study of the cherry insect pest complex in Wisconsin. Ph. D. Thesis. Univ. of Wisconsin, Madison, 155 p.
Essig, E. O. and H. H. Keifer. 1933. A pest of Sierra plums. Monthly BulletinCalif. Dept. of Agric. , 22:153-155.
Forbes, W. T. M. 1923. The lepidoptera of New York and neighboring states. N. Y. Agric. Exp. Sta. Memoir 68: 395p.
Grote, A. 1878. U. S. geological, geographical survey of the territories. 4: 694p.
Haegele, R. W. 1932. Some results with Pyrethrum in control of Mineola scittiella (Hulst). J. Econ. Entomol. 25: 1073-77.
Heinrich. C. 1956. American moths of the subfamily Phycitinae. U. S. N. M. Bull. 207: 11-14.
Houk, W. E. 1950. Studies on the Mineola moth (Mineola scitulella) and other Northern Michigan fruit insects. Masters Thesis. Mich. State Univ. E. Lansing.
Howitt, A. J. and A. Pshea. 1965. The development and use of ultra low volume ground sprayers for pests attacking fruit. Quarterly Bull. Mich. Agric. Exp. Sta., 48: 144-160.
Hulst, G. D. 1900. Some new genera and species of Phycitinae. Can. Entomol. 32:169.
Li, J. C. 1966. Statistical Inference I. Edwards Brothers: Ann Arbor. 658 p.
Newcomer, E. J. 1950. Orchard insects of the Pacific Northwest and their control. U. S. D. A. Circ. 270 rev. 50.
Oatman, E. R. 1964. Bionomlcs of the destructive prune worm, Mineola scitulella on sour cherry in Wisconsin. J. Econ. Entomol. 57: 100—102.
75 76
Oatman, E. R. 1966. Insect injury to sour cherries in the absence of insecticide sprays. J. Econ. Entomol. 59: 30-32.
Pack, H. J. and V. Dowdle. 1930. A wild host of Mineola scitulella. J. Econ. Entomol. 23: 321.
Siegal, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill, New York. 312 p. Steele, R. G. D. and J. H. Torrie. 1960. Principles and procedures of statistics. McGraw-Hill, New York. 481 p.
Shull, W. E. and C. Wakeland. 1941. The Mineola moth or destructive prune worm. Idaho Agric. Exp. Sta. Bull. 242: 1-7.
Wakeland, C. 1930. Work and progress of the agricultural experimental station. Idaho Agric. Exp. Sta. Bull. 170: 20-21.
APPENDIX
Appendix Table 1. -Measurements of number of bud clusters, trunk diameter, tree height, crown diameter, crown height and crown area of eleven tart cherry trees Hart, Michigan - April 18, 1967
Variablesa Trees Diam. Cluster Tr. Ht. Cr. Dia. Cr. Ht. Cr. Area
1 10. 2 2932 170 195 114 69, 800 E
2 8. 9 2787 168 150 120 56, 520 3 8. 6 2467 162 207 108 70, 800 g 4 5 2369 165 252 121 95, 740 h
5 '8. l 1793 174 216 138 94,120
6 7. 2 1616 124 183 78 44, 820
7 6.1 1278 138 144 114 51, 550
8 6. 4 1184 121 144 100 45, 220
9 5. 9 1038 103 135 72 39, 510
10 3 8 740 116 94 80 23,430
11 4.1 728 102 120 79 29, 710
aVariables: Diam. = Trunk diameter in feet measured one foot above the ground Clusters = Number of bud clusters containing at least one fruit bud Tr. Ht. = Tree height in inches measured at the highest point
78 Appendix Table 2. -Occurrence of Acrobasis tricolorella larvae damaged fruit of tart cherry tree Hart, Michigan - July 11, 1967—
Number of infestations recorded in 25 cherries from each quadrant of the tree South South North North Tree QBPGI' Lower Upper Lower Total Mean
1 0 0 0 0 0 2 2 3 3 2 10 2. 5 3 6 2 3 4 15 3. 7 4 4 4 3 2 13 3.2 5 8 17 4 5 34 8. 5 6 1 2 8 2 13 3.2 7 3 2 5 4 14 3. 5 8 3 4 6 6 19 4.7 9 4 7 7 1 19 4. 7 10 6 4 4 5 19 4.7 11 3 2 3 4 12 3.0 12 4 2 2 1 9 2.2 13 2 2 3 4 11 2.7 14 2 2 2 3 9 2.2 15 3 4 5 3 15 3.7 16 1 3 2 2 8 2.0 17 3 3 3 2 11 2.7 18 3 2 5 2 12 3.0 19 4 5 3 2 14 3. 5 20 2 3 2 4 11 2. 7 21 2 1 4 3 10 2.5 22 4 2 3 1 10 2.5 23 0 3 1 1 5 1.2 24 3 4 2 0 9 2.2 25 3 1 1 1 6 l. 5 26 1 10 l 4 16 4.0 27 1 0 0 2 3 .7 28 1 0 6 3 10 2. 5 29 4 0 1 3 8 2.0 30 1 2 5 4 12 3. 0
79 Appendix Table 3.- Summary of Acrobasis tricolorella larvae movement observed at intervals in replicates of tagged terminal bud clusters of tart cherry, Hart, Michigan - 1967
Quadrant April May 111418212528 2 5 9121619232630 South Lager In b 3 l 7 4 4 4 0 0 7 2 1 2 0 O 0 0 Out 0 0 2 2 3 0 1 l 1 4 4 8 l 1 3 l yithinc o 1 1 2 z o o 5 3 o 4 1 z 2 0 Dead 0 0 0 l O 0 O O 0 2 0 0 0 O 0 Total larvae present 3 20 22 23 24 24 23 29 30 25 23 15 4 1 0 South Upper In 0 3 8 3 4 2 0 3 0 2 3 0 O 0 0 Out 0 0 0 2 1 l 0 1 O 1 3 1 6 8 1 Within 0 0 0 1 0 l 0 1 0 l 2 0 1 O 0 Dead 0 0 0 0 0 0 0 0 1 2 O 0 O 0 0 Total larvae present 0 3 ll 12 15 16 16 18 17 16 16 15 9 l 1 North Lower In 2 l 2 3 2 4 1 l 7 1 2 0 l O 0 0 Out 0 0 0 l O l 1 l 0 4 3 5 8 8 0 Within 0 0 4 2 2 4 O l l 1 3 l 0 0 0 Dead 0 0 0 0 l 0 0 1 O 0 l l 6 0 0 Total larvae present 2 14 17 18 21 21 21 26 27 25 21 16 8 0 0 North Upper In 0 3 7 1 4 l 2 9 2 O 1 l 0 0 0 Out 0 O 0 1 l 2 0 O 0 2 4 2 8 6 2 Within 0 0 O 0 0 l 0 0 0 0 5 0 2 2 0 Dead 0 0 O 0 1 l 0 0 0 0 1 0 0 0 0 Total larvae present 0 3 10 10 12 10 12 21 23 21 17 16 8 2 0 Grand Total In 5 35 22 10 15 4 3 25 5 5 6 2 0 O 0 Out 0 0 2 6 5 4 2 3 1 1 1 14 15 33 25 4 Within 0 1 5 5 4 6 0 7 7 2 14 2 5 4 0 Dead 0 O 0 l 2 1 0 1 1 4 2 1 O 0 0 Total larvae present 5 4O 60 63 72 71 72 93 96 86 76 62 29 4 0
a) In = First observation of a larvae in a tagged bud cluster b) Out = First observation of the absence of a larvae previously present in a tagged bud cluster c) Within = The observation of an In and Out in the same
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