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This is to certify that the

thesis entitled

TOXICITIES OF AZINPHOSMETHYL AND OTHER
APPLE ORCHARD PESTICIDES TO THE APHID

‘REDATOR, Aphidoletes aphidimyza (RONDANI)

 

(DIPTERA: CECIDOMYIIDAE)
presented by

Leslie A. Warner

has been accepted towards fulfillment
of the requirements for

M - s - degree in W

 

Major %fessor

 

Date I/AZY/Y/
// l

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OVERDUE FINES:
25¢ per day per item

RETUMING LIBRARY MATERIALS :

Place in book return to remove
charge from circulation records

 

TOXICITIES OF AZINPHOSMETHYL
AND OTHER APPLE ORCHARD PESTICIDES
TO THE APHID PREDATOR, Aphidoletes a hidim za (RONDANI)
(DIPTERA: E MYI D

By

Leslie A. Warner

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE
Department of Entomology

1981

ABSTRACT
TOXICITIES OF AZINPHOSMETHYL
AND OTHER APPLE ORCHARD PESTICIDES

TO THE APHID PREDATOR, A hidoletes a hidim za (RONDANI)
(DIPTERA: CECIDOHYI D

By

Leslie A. Warner

Aphidoletes aphidimyza, a cecidomyiid predator of

 

apple aphids, was tested for toxicities to azinphosmethyl
and several registered and experimental pesticides.
Mortalities from azinphosmethyl in eggs collected from 14
field sites differing in previous pesticide exposure re-
vealed significantly higher LCSO values in populations
taken from commercial orchard sites; the largest resistance
ratio was 14. Among the life stages, LCSO ratios for
azinphosmethyl ranged from 1 to 6-fold, with first instars
the most susceptible and eggs the least. Egg mortality

was greatest in embryos exposed just prior to eclosion.

Egg and third instar mortalities were evaluated for 28
pesticides at concentrations equivalent to recommended
field rates, and pesticides were grouped into three classes:
those causing high mortality (>50%) in both stages
(diazinon, methomyl, carbaryl, demeton, dimethoate,
azinphosmethyl); those causing high mortality in one stage
only (oxythioquinox, phosmet, permethrin, fenvalerate,
oxamyl); and those causing low mortality (<30%) in both
stages (phosalone, phosphamidon, carbophenthion, pirimicarb,

plus several fungicides and miticides).

ACKNOWLEDGMENTS

I would like to express my gratitude to my major
professor, Dr. Brian A. Croft, for suggesting this project
and assisting me in its development and completion. I
would also like to extend my appreciation to the members
of my Guidance Committee, Dr. Alan L. Jones, Dr. Mark E.
Whalon, and Dr. Frederick W. Stehr, for their suggestions
and criticisms.

I wish to thank my family and friends for their
assistance and support, with special thanks to Joseph G.
Morse for the use of his reference materials. Finally, I
gratefully acknowledge the challenges and opportunities
provided me by the Department of Entomology at Michigan

State University.

ii

TABLE OF CONTENTS

LIST OF TABLES . . . . . . . . . . . . . . . . .
LIST OF FIGURES . . . . . . . . . . . . . . . .
INTRODUCTION . . . . . . . . . . . . . . . . . .
LITERATURE REVIEW . . . . . . . . . . . . . . .
I. Tolerance and Resistance . . . . . .

II. Apple Aphid Control . . . . . . . . .

III. Aphidoletes aphidimyza . . . . . . .

 

MATERIALS AND METHODS . . . . . . . . . . . . .
I O OverVieW O O O O O O O O O O O O O C
II. Collection and Rearing . . . . . . .

III. Comparison of Life Stage Suscepti-
bilities to Azinphosmethyl . . . . .

IV. Susceptibilities of Field Populations
to Azinphosmethyl . . . . . . . . . .

V. Toxicities of Orchard Pesticides When
Applied at Recommended Field Rates .

RESULTS AND DISCUSSION . . . . . . . . . . . . .

I. Life Stage Susceptibility to
Azinphosmethyl . . . . . . . . . . .

II. Susceptibilities of Field Populations
to Azinphosmethyl . . . . . . . . . .

III. Toxicities of Orchard Pesticides . .
CONCLUS ION O O O O O O O O O O O O O O O O 0 O 0
LIST OF REFERENCES . . . . . . . . . . . . . . .

iii

Page
iv

vi

00‘be

13
13
14

15

22

24
28

28

42
53
63
67

Table

10.

11.

LIST OF TABLES

Laboratory toxicity of orchard pesticides
to eggs and larvae of A. aphidimyza (from
Adams and PrOkOpy 19777—0 O O O O O O I O O

 

Laboratory toxicity of azinphosmethyl
(0.62 1b/100 gal) to eggs and larvae of
two populations of A. aphidimyza (from
Adams and Prokopy 19777fi. . . . . . . . .

 

List of pesticides tested for toxicity to
A—0 aphidimyza O O O .' O O O O O O I O O O O

 

Contingency table analysis of A. aphidimyza

 

egg mortality: azinphosmethyl—End cohort
effects (after Zar 1974) . . . . . . . . .

Contingency table analysis of A. aphidimyza

 

egg mortality: azinphosmethyl—5nd day of
met S ion 0 C O O O O O O O O O O O C O O C

Kruskal-Wallis test for effects of time of
immersion in azinphosmethyl on egg mortal-
ity in A; aphidimyza . . . . . . . . . . .

 

Contingency table analysis of A. aphidimyza

 

egg mortality: azinphosmethyl—3nd_age of
eggs I O O O O 9' O O O O O 0 O O O O O O O

Probit analysis of susceptibilities of A.

a hidim za life stages to azinphosmethyI_
(1975 source) . . . . . . . . . . . . . . .
‘Mean LCSO values for susceptibilities of

A. a hidim za life stages to azinphosmethyl
TI97E source} . . . . . . . . . . . . . . .
Comparison of A. a hidim za larval weights
and correspondifig ECSO values . . . . . . .
Probit analysis of susceptibilities of A.
aphidimyza life stages to azinphosmethyI—

source) 0 O O O O O O O O O O 9 I O 0

iv

Page

12

26

31

31

33

33

35

37

39

39

Table Page

12. Comparison of azinphosmethyl sources (1976
vs. 1980) for life stages of A; aphidimyza . 4O

 

13. Percent mortalities from azinphosmethyl in
field-collected eggs of A; aphidimyza . . . . 43

 

l4. Probit analysis of mortalities from azin-
phosmethyl in field-collected eggs of A;
aphidimyza . . . . . . . . . . . . . . . . . 44

 

15. Comparison of population means for A;
aphidimyza egg susceptibilities to azin-
phosmethyl . . . . . . . . . . . . . . . . . 46

 

16. Comparison of A; aphidimyza egg LCSO values
for laboratory colonies and field
populations . . . . . . . . . . . . . . . . . 50

 

l7. Azinphosmethyl susceptibility in first in-
star larvae of field-collected populations
of A; aphidimyza . . . . . . . . . . . . . . 51

 

18. Comparison of azinphosmethyl LCSO values
for eggs and first instars of field-
collected A; aphidimyza . . . . . . . . . . . 54

 

19. Comparison of A; aphidimyza third instar
mortalities from azinphosmethyl for two
types of test chambers . . . . . . . . . . . 55

 

20. Pesticides causing high mortality in eggs
and larvae of A; aphidimyza . . . . . . . . . 56

 

21. Pesticides causing stage-selective
mortality in eggs and larvae of A;
aphidimyza . . . . . . . . . . . . . . . . . 57

 

22. Pesticides causing low mortality in eggs
and larvae of A; aphidimyza . . . . . . . . . 58

 

23. Mortalities caused by orchard pesticides
in life stages of A; aphidimyza, from two
separate studies . . . . . . . . . . . . . . 6O

 

LIST OF FIGURES
Figure Page
1. Types of test chambers used to assess

toxicities of pesticides to larvae of
A; aphidimyza . . . . . . . . . . . . . . . . 19

 

2. Mortality of A. aphidimyza eggs after
immersion in azinphosmethyl (. 02% a. i. )
at various times during two consecutive
days . . . . . . . . . . . . . . . . . . . . 29

 

3. MOrtality of A. aphidimyza eggs after
immersion in azinphosmethyl (. 02% a. i. )
at various ages . . . . . . . . . . . . . . . 30

 

4. Susceptibility to azinphosmethyl of life
stages of a laboratory colony of A.
aphidimlza O O O O O O O O O O O O O O O O O 41

 

5. Susceptibility to azinphosmethyl of A.
aphidimyza eggs collected from commercial
and‘research apple orchards (C+R) . . . . . . 47

 

6. Susceptibility to azinphosmethyl of A.
aphidimyza eggs collected from areas of
little or no pesticide exposure (N+L) . . . . 48

 

7. Susceptibility to azinphosmethyl of A.
aphidimyza first instar larvae collected
from laboratory and field populations . . . . 52

 

vi

INTRODUCTION

Since the commercial development of synthetic organic
pesticides, agriculture has relied heavily on chemicals to
reduce populations of arthropod pests and prevent excessive
damage to crops. Mere recently integrated pest management
(IPM) has been applied in several crop systems with some
success (e.g. deciduous tree fruits), and expansion of
these programs is likely (Blair and Edwards 1980). With
IPM, all available pest control techniques are evaluated
and consolidated into a program to manage pest populations
so that economic damage is avoided and adverse side
effects on the environment are minimized (NAS 1969).
Future expansion of IPM programs will probably emphasize
the integration of the complex interactions among species
(Newsom 1980).

Pesticides are effective tools when utilized judi-
ciously in IPM programs, but excessive application can
produce undesirable effects, including the development of
resistance and cross-resistance, problems which frequently
necessitate further pesticide application and increase the
costs of crop production. In commercial apple orchards
none of the insect pests which directly attacks the fruit

has developed resistance to the pesticides currently

2

registered. With nearly zero tolerance of pest damage to
the apples, and since no program for biological control of
these direct pests is available, protection of the fruit is
likely to continue to depend on insecticide applications.

Many secondary pests of apple (i.e. aphids and phyto-
phagous mites) have acquired a degree of resistance to the
compounds applied to control direct pests. Croft and Hoyt
(1978) reviewed the current status of apple IPM, noting
the adaptations of natural enemies to these pest complexes.
In Michigan orchards azinphosmethyl is the principal broad-
spectrum insecticide applied, and strains of the predatory

mite, Amblysieus fallacis (Garman), have acquired resis-

 

tance to this compound. Croft (1975) has developed an IPM
program for mite control in Michigan apple orchards,
relying on the maintenance of suitable predator:prey ratios
through the use of selective insecticides and cultural
practices. To maintain and possibly expand the benefits
of this IPM program, potentially non-disruptive control
techniques should be examined for management of other
secondary apple pests.

Among the indirect pests of apple are two species of

aphids (Aphis pomi De Geer, Dysaphis plantaginea

 

(Passerini)) which can decrease yield and growth. To
prevent or limit damage, growers typically apply systemic
and broad-spectrum contact insecticides. Developing an
integrated control program for aphids could reduce the

amount of pesticides applied in the orchard while causing

3

less disruption of existing natural enemy populations.

One of the first steps in developing an IPM program
is identifying the predators of the pest species.
Recently a cecidomyiid, Aphidoletes aphidimyza, has been
found preying on apple aphids with increasing frequency
(Adams and Prokopy 1977). Several characteristics of this
species contribute to its potential as a biological control
agent (Markkula et al. 1979a). This study was undertaken
to assess the mortality rates in A; aphidimyza after
exposure to those pesticides likely to be applied in
Michigan apple orchards, with the results contributing to
pesticide recommendations in an apple IPM programs
Specifically the objectives of this work were:

1) To determine the susceptibilities of

the life stages of A; aphidimyza to the lethal

 

effects of azinphosmethyl.

2) To determine the levels of resistance

 

of populations of A; aphidimyza in commercial
apple orchards in Michigan.

3) To determine the susceptibility of
eggs and third instar larvae of A; aphidimyza
to pesticides commonly applied in Michigan

apple orchards.

LITERATURE REVIEW

I. Tolerance and Resistance

Resistance of arthropods to pesticides includes 414
species (Georghiou 1979) of which 10 are natural enemies
(FAO 1979). Quantitative assessments of resistant popula-
tions of a species can be obtained through dosage-mortality
bioassays, using the standardized method of detection (FAO
1969). Georghiou and Taylor (1977a) have classified the
factors affecting the development of resistance in pests,
and several investigators have discussed the factors caus-
ing differential frequency in resistance development between
pests and their natural enemies (Croft and Brown 1975,
Morse 1978, Croft and Morse 1979).

Croft and Brown (1975) have reviewed the factors which
influence the susceptibility of arthropod natural enemies

to pesticides. Direct toxic effects

,_. . v”, —-—.-.‘..._...1 7-- __ , ‘_

of compounds can be

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developmental stageflandmlevels of nourishment. Indirect

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.__“_ "_ .-.....____ _ .. n.

.r-

effects of pesticides include the elimination of the food
source for natural enemies, secondary poisoning following
consumption of contaminated prey, and the effects of sub-
lethal doses of pesticides on longevity, development, and

reproductive rates of the natural enemy. Direct and

4

5
indirect effects of pesticides interact with the genetic,
biological, and operational factors outlined by Georghiou
and Taylor (1977b) to determine the likelihood of resis-
tance in a beneficial species.

Many arthropod species are inherently tolerant of the
effects of pesticides; when tested for toxicity, pOpulations
with no previous exposure to a given compound or related
chemicals exhibit little mortality. Developmental stages
of a species may exhibit tolerance: in tests of the green

lacewing, Chrysopa carnea Stephens (Bartlett 1964a), eggs

 

were less susceptible to pesticides than adults, with
larvae intermediate. Bartlett (1964b) generalized these
results to include all holometabolous predators and para-
sites. Pupae are generally less susceptible to the effects
of pesticides than larvae (Rettich 1980, Singh and Rawat
1980). Colburn and Asquith (1971) tested fourteen pesti-

cides on all stages of the lady beetle, Stethorus punctum

 

(LeConte), and pupae were tolerant of all but carbaryl.
No trend in tolerances among other stages was evident,
possibly indicating the importance of mode of pesticide
action and uptake.

Mortality within a developmental stage may vary with
the size, weight, sex, and physiological state of the

subjects. Recentlyamolted Heliothis spp. were more

 

susceptible than larvae with full cuticular development
(Mullins and Pieters 1980). Exposing coccinellid eggs to
chlordimeform when old (48-72 hrs) and young (<24 hrs)

 

rn

01

0f

6
resulted in greater susceptibility in the more developed
embryos (Streibert and Dittrich 1977). Elliot and Way
(1968) tested the toxicities of systemic aphicides on eggs
of two predatory anthocorid species. Unhatched eggs
consistently contained embryos that had died just prior to
hatch irrespective of egg age when treated, an effect of
organophosphorous insecticides reported by Smith and
Salkeld (1966).

The susceptibilities of A; aphidimyza eggs and third

 

instar larvae were tested by Adams and Prokopy (1977);

total egg mortality was determined by counting unhatched

eggs and dead newly-hatched larvae. No consistent
differences among stages is evident (Table 1), although
certain compounds may be stage-selective (i.e. azinphosmethyl
and demeton). Stage tolerance may depend on properties of
the pesticide as much as on the physiology, development,

and ecology of the species.

II. Apple Aphid Control

,Rosyapple aphids (Dysaphis plantaginea (Passerini))

 

 

and green applgfiaphids (Aphis pomi DeGeer) are the most

 

 

frequent andfiabundant aphid pests in Michigan apple

 

orghards (Brunner and Hdwittul98l). Detailed biologies of
these pests have been reported by several investigators
(Matheson 1919, Lathrop 1928, Blackman 1974). Many species
of natural enemies attack these aphids, including members

of the following insect families: Syrphidae, Coccinellidae,

7

 

 

 

 

 

Table 1. Laboratory toxicity of orchard pesticides to

eggs and larvae of A; aphidimyza (from Adams

and Prokopy 1977).

Percent Mortality
Concentration Early first Late

Compound (amt/100 gal) Egg instar instar
Phosmet SOWP 1.50 lb 8 24 18
Azinphosmethyl 50W? 0.62 lb 86 14 18
Endosulfan 50WP 1.00 lb 6 29 46
Demeton 6EC 0.31 pt 8 57 32
Phosalone 3EC 1.50 pt 4 0 10
Carbaryl 50WP 1.00 lb 72 21 -
Phosphamidon 8EC 0.25 pt 34 27 16
Cyhexatin SOWP 0.31 lb 14 0 12
Propargite 30WP 1.50 lb 6 2 -
Thiram 50W? 2.00 lb 6 0 8
Captan 50W? 1.00 lb 8 2 6
Control (H20) - - 4 0 8

 

8
Anthocoridae, Miridae, Cecidomyiidae, Ichneumonidae,
Cynipidae, Chamaemyiidae, Ceraphronidae, and Chrysopidae
(Evenhuis 1961, Oatman and Legner 1961, Westigard and
Madsen 1965, Holdsworth 1970, Specht 1972, Adams and
Prokopy 1977). Typically pesticides are applied when aphid
populations approach unacceptable levels, and field studies
have indicated which pesticides are aphicidal (Madsen and
Bailey 1959, Pielou and Williams 1961 a,b, Madsen et a1.
1961, Cessac 1963, Asquith 1967, 1970, Forsythe and Hall
1973, Forsythe 1976). Several of the recommended insecti-
cides produce satisfactory knockdown, but reinfestation
and resurgence can occur quickly. Other compounds produce
good aphid control but disrupt predator:prey complexes,
especially in mites. Another drawback to chemical control
is the development of resistance to organophosphorous
compounds in £1.2293 and to cyclodienes in the wooly
apple aphid, Eriosoma lanigerum (Hausmann) (Georghiou and
Taylor 1976).

\/
"31 Several integrated approaches to apple aphid control

 

.EéYfimbeen.attempted with varying degrees of success
_reported (Holdsworth 1970, Bonnemaison 1972, Madsen et al.‘
1975). Adams and Prokopy (1977) proposed an integrated
control program.for Massachusetts based on biological

control by the predatory cecidomyiid midge, A; aphidimyza,

 

recommending selective pesticide use for control of major

pests. Expansionof this program has included monitoring

—.

of aphid and midge densities, using action thresholds, and

9
implementing a predator:prey index to keep aphid popula-

tions below damaging thresholds (Prokopy et a1. 1980).

III. Aphidoletes aphidimyza

Taxonomic confusion has surrounded the aphidophagous
cecidomyiids, but several recent studies have helped
clarify the species of this family (Harris 1966, 1973,
Nijveldt 1969). Gagne (1971) found only three valid

species of Aphidoletes described for North America, with

 

A; aphidimyza by far the most abundant and widespread. The

biology of A; aphidimyza has been reviewed extensively

 

(Barnes 1929, Harris 1973, Markkula et al. 1979a, Adams
and Prokopy 1980). Adults (2mm) are active at dusk and
nocturnally; honeydew secreted by aphids is utilized as a
food source. This species is monogenic (Sell 1976) and
each female lays approximately one hundred eggs in several
small clusters, usually on the underside of aphid-infested
leaves. Females are able to locate aphid colonies even

at very low densities (El Titi 1973).

Eggs are 0.3mm long, smooth, and orange. Larvae
hatch in two or three days, growing to 2.5 or 3mm at
'maturity (7-14 days). Three instars are generally reported
although Azab et al. (1965) found evidence for four. Over
60 species of aphids have been reported as food sources
(Harris 1973). Larvae usually attack aphids by piercing
their leg joints, paralyzing the aphid and dissolving its

internal structures; the desiccated body remains attached

10
to the leaves by the mouthparts.

Reports of average larval consumption of aphids have
varied, depending on aphid species, age, and density.
Humidity, temperature, sex of larvae, and intra-specific
competition also affect consumption (Markkula et al. 1979a).
In an apple terminal caging study, Adams and Prokopy (1980)
found the consumption of é;.EQEi per cecidomyiid larva
varied between 4 and 65, with mean consumption of 27.9.

Larvae of this midge usually pupate in the soil,
forming cocoons at a depth of 3cm, although cocoons may be
found occasionally on the host plant. Adults usually
emerge after 7 to 14 days. Diapause begins in September
after several generations have been completed. Larvae
overwinter in cocoons and pupate in spring, emerging in
Michigan within the first two weeks of June (Morse, un-
published data).

Several investigators have tested the effects of some

pesticides on A; aphidimyza. Markkula et al. (1979b)

 

assessed the toxic effects of two_fungicides and four
insecticides when applied to the pupation medium. The
fungicides were not toxic to the midge but the insecticides
caused 80% or greater mortality, and their use is not
recommended for soil applications. Several acaricides are
considered safe for foliage applications in greenhouses
(Markkula and Tiittanen 1976). The ovicidal activity of
methomyl was tested by David et a1. (1980). Their results

indicate high toxicity to midge eggs, even at one-fourth

11
the recommended rate of field application for Michigan
(Jones et a1. 1980).
Adams and Prokopy (1977) completed an evaluation of
mortalities caused by several apple orchard pesticides in

two life stages of A; aphidimyza. Eggs and late instar

 

larvae were collected from a research apple orchard which
had received no insecticide or miticide treatment for six
years. These were exposed to ten pesticides at concentra-
tions equivalent to recommended field rates. Mortalities
were calculated for the egg stage, early first instars, and
late instars (Table 1, p. 7). Endosulfan and phosmet were
only moderately toxic to the stages tested, and since
these compounds are of low toxicity to predatory mites,
their use was suggested in control programs for both aphids
and mites.

Evidence of resistance in the midges to azinphosmethyl
was also reported. Eggs and larvae were collected from
two sources, a commercial orchard and the untreated research
orchard. ‘Mortalities observed in the two samples may
indicate resistance to the insecticide (Table 2). In their
toxicity tests only fifty individuals were exposed to
each pesticide, and the results may be complicated by

starvation effects.

12

 

 

 

 

 

Table 2. Laboratory toxicity of azinphosmethyl (0.62 1b/
100 gal) to eggs and larvae of two populations
of A;_aphidimyza (from Adams and Prokopy 1977).
Percent Mortaligy
Type of Early first Egg and early Late
Orchard Egg instar first instar instar
Abandoned 86 14 88 18
Commercial 6 38 42 6

 

MATERIALS AND METHODS

I. Overview

Studies were designed to determine the physiological

toxicities of pesticides to the life stages of A; aphidimyza

 

and to detect resistance in orchard populations of this
predator. Susceptibilities to azinphosmethyl were compared
among the life stages of a single strain and among eggs of
laboratory colonies of different origins. To detect
resistance, LCSO values were estimated for eggs collected
from 14 sites differing in pesticide exposure. To assess
differential susceptibility in life stages among strains,
first instar LCSO values for 4 populations were compared
with corresponding egg susceptibilities. Toxicities of
registered and experimental pesticides were evaluated for
eggs and third instars of a laboratory colony.

Each developmental stage was exposed to compounds in
a manner reflecting pesticide uptake in the field, al-
though complete coverage of eggs and larvae was ensured
through immersion to reduce variation attributable to
differential exposure. LC50 values were estimated with
probit analysis (Finney 1970), utilizing either the M.S.U.
computer program.BNPGPROBITANALYSIS or a package developed
by this author for use with a programmable calculator

13

l4
(Hewlett-Packard 25).

II. Collection and Rearing

Cecidomyiids were collected from the field using one
of two methods: 1) gathering apple leaves infested with
aphids and midge larvae, or 2) placing aphid-infested trap
plants at the collection site to attract ovipositing
females. With the first method, second and third instar
larvae were transferred to fava bean plants (Vigia spp.)

which were heavily infested with pea aphids (Macrosiphum

 

pi§i_Harris). Plants were placed in screened cages (60 x
75 x 45cm) with sand and/or Vermiculite sprinkled on the
cage floor; larvae dropped to the cage floor or soil sur—
face to pupate. After one week aphid-infested bean plants
were placed in the cage for oviposition by emerging adults.
Rearing continued by placing plants with eggs in new cages
where larvae developed. After pupation plant stems were
'cut to soil level and new plants were added after adult
emergence.

In the second method aphid-infested bean plants were
placed at the field collection site for one to three
nights. To ensure egg collection, each pot of 5-6 plants
was placed 25m from all other pots. Plants were retrieved
and placed in rearing cages where the rearing process pro-
ceeded as described above. Approximately one hundred
larvae were needed to establish a viable colony. Samples

of males collected after rearing in 1979 were identified to

15

species, and only A; aphidimyza was found among the

 

collected specimens.

III. Comparison of Life Stage Susceptibilities
to Azinphosmethyl

Most of the following experiments were conducted with
individuals collected from a laboratory colony which
originated from the Graham Research Station of Michigan
State University, near Grand Rapids, Michigan. The original
sample was collected from orchards which.were treated with
azinphosmethyl several times per season for many years.
In the egg development study, the source of eggs was a
colony which originated from a commercial orchard near
Grand Rapids, Michigan (i.e. Anderson), and had received

similar azinphosmethyl treatments.

A. Susceptibility to Azinphosmethyl - Eggs

 

A modified slide dip method (Nakashima and Croft
1974) was used to assess the LCSO for the egg stage. Eggs
were collected from the laboratory colony on bean plants
and transferred to double-stick tape (13xl3mm) affixed to
one end of a microscope slide. Twenty to thirty eggs were
placed on each slide in rows of five or six. Eggs are
usually laid in clusters of 3-20. To increase genetic
variability per slide and minimize bias, no more than four
eggs from each cluster were placed on each slide.

Slides with mounted eggs were held in a high humidity

chamber consisting of a damp sponge in a clear plastic

16

box while pesticide solutions were prepared. Eggs on each
slide were inspected for damage; those injured during
transfer appear shriveled, and the number was recorded on
a tag attached to each slide, along with total eggs present.
Subtraction of damaged from total eggs yielded the number
of viable eggs considered in each treatment. Overall
control mortality was assessed with a water dip for each
experiment.

Each slide was randomly assigned to a dose and dipped
(5 sec), drained, and allowed to dry for ten minutes, then
placed in the humidity chamber at room temperature (21-25°C)
under 16 hours of fluorescent light. Newly-hatched larvae
can crawl across the tape; to prevent larval starvation,
aphids were added to each slide prior to hatch. Unhatched
eggs and dead larvae found on the tape were counted 72
hours after immersion, and egg mortality was determined for
each dose. Larval mortality was nearly zero and was
ignored in the mortality calculations. Mortalities were
corrected for control mortality using Abbott's formula
(1925), then probit analysis was applied to estimate the
population LCSO. Two sources of azinphosmethyl were used,
both formulations being wettable powders with 50% active
ingredient (a.i.) but differing in the year of production:
1976 and 1980. The tests were replicated five times using
the 1976 azinphosmethyl, once with the 1980 source.

To determine the susceptibility of A: aphidimyza eggs

 

as a function of embryological development, eggs were

l7
immersed in a .02% a.i. solution (1976 source) at different
time intervals. Eggs were collected from the Anderson
colony at two time periods, from 7 to 10 p.m. and 4 to 7
a.m., on two different nights. Eggs within each group
(p.m. and a.m., respectively) were considered to be at the
same stage of development 1 1.5 hours, with a nine hour lag
in the a.m. group. Eggs were mounted on slides and randomly
assigned to a time for immersion in the previously deter-
mined LC50 solution. The times for dipping were spread
over two days as follows: Day I = 9 a.m., 1 p.m., 6 p.m.;
Day II = 9 a;m., l p.m., 6 p.m. Eggs were placed in a
humidity chamber until time of immersion, then dipped and
returned to the chamber until hatch, with aphids added to
each slide as previously described. Mortality was cal-
culated for each time of immersion, and contingency tables
were used to analyze the results, comparing day of dip,
time of dip, and age of eggs when dipped to determine

whether a period of greater susceptibility exists.

B. Susceptibility to Azinphosmethyl - Larvae

 

All instars were immersed in solutions of azinphos—
methyl, and they also contacted residues during their
movements after immersion, Field exposure is reflected by
this method since larvae may contact the spray and residue
during movement across the leaves. Estimates of LCSO
values were obtained by exposing groups of larvae to
different concentrations of azinphosmethyl, with water as

the control, using corrected mortalities in probit analysis.

18

Two types of larval test chambers were constructed.
Type I (Figure 1) consisted of a transparent plastic
medicine vial (4.5 x 2.5 cm) with snap cap top. The
bottom of each vial was cut off, the edge flamed, and
another cap with extended sides was inserted. A section
of fine mesh screen was attached to the snap cap by melting
the edges into the plastic. Type II test chambers (Figure
l) were made from translucent nalgene vials (5.6 x 2.5 cm)
with snap cap tops. Bottoms were removed and the top
section of a 2.4 cm diameter vial was inserted to seal
the chamber; fine mesh screening was attached to the snap
cap. The major difference between chamber types was the
fit of the bottom caps. Type I caps contacted the chamber
tube at the flamed edge, leaving a gap between the tube
and extended side of the cap where larvae were sometimes
trapped. Type II caps contacted the chamber tube at the
rim of the cap, about 1 cm into the tube.

The general larval test method consisted of removing
the bottom cap and placing larvae on the sides of the
chamber near the snap cap. The chamber was immersed in
the pesticide solution for five seconds, then drained and
blotted dry for 15 seconds. Aphids were added to the
chamber (approximately 1.5 aphids per larva) and the bottom
cap was inserted. The chamber was allowed to dry for one
hour, then it was placed in a humidity chamber for the
duration of the experiment. Specific details for each in-

star follow.

l9

 

 

TYPE I

 

TYPE II

Figure 1.- Types of test chambers used to assess toxicities of
pesticides to larvae of A. aphidimyza.

20

Twenty first instars (.6 mm long) were transferred to
each Type II test chamber; to increase genetic variability,
no more than five larvae from each leaf were placed in
each chamber. After immersion and addition of aphids, the
chambers were placed on their sides to dry, then placed in
the humidity chamber for 24 hours. Numbers of dead larvae
were recorded, with death defined as the inability to
'withdraw from the touch of a brush. Some surviving larvae
crawled through the screening thus accurate counts of
survivors could not be made. Mortality was calculated by
dividing the number dead by the total number tested for
each dose. Three replications of the LCSO estimate were
made for the 1976 source of azinphosmethyl, one for the
1980 source.

Second instar larvae selected for testing were approx-
imately 1.2 mm long. Mortality was calculated by dividing
the number dead by the total number remaining in the
chamber after 24 hours. This test was replicated four
times with the 1976 azinphosmethyl and once with the 1980
source.

Third instars were approximately 2.3 mm long and were
much more active than first and second instars; when
handled they attempted to crawl away from the disturbance.
TWenty larvae were placed in each Type I chamber which was
immediately dipped and drained. Aphids were then added,
and the bottom cap, containing Sec of moistened sand, was

inserted; the chamber remained upright throughout the test.

21
Larvae crawled down the sides, feeding on aphids, and
survivors pupated in the sand. Aphids were added for
three consecutive days, and dead larvae were counted on
the fourth day. There were three replicates of this test
using the 1976 source of azinphosmethyl and one test with

the 1980 source.

C. Susceptibility to Azinphosmethyl - Adults

 

Adults cling to groundcover vegetation during the day,
thus their primary exposure to azinphosmethyl is probably
from residue contacted as they explore leaf surfaces. To
estimate LCSO values for adults, residual toxicity was
tested. Mason jars were thoroughly rinsed with the solution
of azinphosmethyl (or water for controls) then drained and
allowed to dry for one hour. Adults require a nutrient
source for prolonged survival (Uygen 1971); a 1% honey and
water solution was made available in the jars by soaking a
small cellulose sponge with the solution and placing it in
a small plastic cup. Males and females which had emerged
within the previous 24 hours were collected from the rear-
ing cage with an aspirator and were introduced to the
treated jars. The rims were covered with fine-mesh cloth
and rubber bands secured these. The number of dead adults
in each jar was counted after one hour to determine
mortality caused by handling, then the jars were placed in
a tray of water at room temperature under 16 hours of
light. Prolonged contact with the insecticide was likely

since flies preferred clinging to the sides of the jars

22
rather than the screening. Dead and live flies were
counted after 24 hours, with death defined as immobility
and usually coinciding with a prone position at the bottom
of the jar. Mortality was calculated after deducting the
first hour deaths, and probit analysis was applied to the
corrected mortalities. The test was replicated three times

using the 1976 source of azinphosmethyl.

IV. Susceptibilities of Field Populations
to Azinphosmethyl

A. Eggs

In August 1980 cecidomyiid eggs were collected from
fourteen separate sites in the southern half of the lower
peninsula of Michigan. Each site can be classified in
one of four categories:

1) N = no known pesticide exposure; nature
preserves or wildlife experiment stations.

2) L = low probability of pesticide exposure;
recently abandoned apple orchards or sites
where pesticides may have been used but
only infrequently and inconsistently.

3) C = commercial apple orchards where pesti-
cide use is frequent and consistent, and
azinphosmethyl is applied several times
each season.

4) R = research orchards at fruit stations of

Michigan State University, where pesticide

23
use is frequent and azinphosmethyl is
applied several times each season.

Eggs were collected by placing aphid-infested trap
plants around the collection site late in the afternoon,
with eight to twelve pots per site. Early the following
morning, all pots were retrieved and returned to the
laboratory where eggs were promptly mounted on slides and
dipped in solutions of the 1980 azinphosmethyl source.

The ubiquitous presence of A; aphidimyza was evidenced by

 

the effectiveness of this method; wherever plants were
placed, eggs were found. Probit analysis was campleted
for each data set; to compare LC50 values, a t-test was
used for two groups, low vs. high probability of azinphos-
methyl exposure (N+L,C+R, respectively).

Colonies of A; aphidimyza established from field-

 

collected samples were also tested for egg susceptibilities
to the 1976 azinphosmethyl source. Probit analysis of the
resulting mortalities provided estimated LCSO values for
each population after colonization under laboratory condi-
tions. The names assigned to the colonies tested are:
Anderson, Graham, MSU, Klein, Warren, Rose Lake. Popula-
tion locations and pesticide exposure histories are listed

in Table 14, p. 44.

B. First Instar Larvae

 

When a sufficient number of eggs remained after
completing the egg susceptibility tests, the first instars

hatching on the bean plants were also treated, using the

24
methods previously described. L050 values were estimated
for each population, and ratios of egg LCSO to first in-
star LC50 were compared to determine the constancy of the
magnitude of the difference between stages among the

different exposure histories.

V. Toxicities of Orchard Pesticides
When Applied at Recommended Field Rates
A wide range of pesticides is currently registered
for use on apples in Michigan, and several others are
likely to be approved in the near future. Those compounds
frequently applied by growers and some approved for
experimental purposes were tested for mortalities produced

in the two life stages of A; aphidimyza. Concentrations

 

applied were those equivalent to maximum recommended field
rates in the 1980 Fruit Pesticide Handbook (Jones et a1.
1980), and are listed in Table 3. Eggs and third instar
larvae were tested using methods similar to those described
in Section II (A,B) with the following exceptions:

l) MOrtalities for the first instar larvae which died on
the tape were recorded and used in assessing the total
mortality for the egg stage; 2) Third instar mortality

was calculated after counting the number of emerged adults,
usually two weeks after the immersion. Mortalities for
eggs, early first instars, and third instars plus pupae

are presented for comparison for each pesticide. Egg tests

were replicated three or four times, with resulting

25
mortalities averaged, while larval tests were replicated

twice.

26

Table 3. List of pesticides tested for toxicity to A;

 

 

 

 

 

 

aphidimyza.
Compound Formulation $3103 :21) (Iggczi7lgsiggl)
ORGANOPHOSPHATES
Dimethoate 4EC 1 pt 0.50
Diazinon 4EC 1 pt 0.50
Azinphosmethyl 50WP .5 lb 0.25
Phoamet 50WP 1 1b 0.50
Phosphamidon BBC .25 pt 0.25
Demeton 6EC .33 pt 0.25
Carbophenthion BBC .25 pt 0.25
Phosalone BBC 1 pt 0.38
CARBAMATES
Methomyl 1.8L 2 pt 0.45
Pirimicarb 50WP .25 1b 0.06
Carbaryl 808 1.25 lb 1.00
Oxamyl 2L 1 pt 0.25

SYNTHETIC PYRETHROIDS

 

Permethrina 2EC .4 pt 0.10
Permethrinb 3.2EC .25 pt 0.10
Fenvalerate 2.4EC .33 pt 0.10

CHLORINATED HYDROCARBONS
Dicofol 35W? 1.33 1b 0.47

 

Endosulfan 3EC 1.33 pt 0.50

27
Table 3. Continued

 

 

 

 

 

 

Field Rate Concentration
Compound Formulation (/100 gal) (lbs ai/100 gal)
MISCELLANEOUS
Oxythioquinox 25W? .5 lb 0.12
Propargite 6EC .5 pt 0.38
Cyhexatin 50WP .38 lb 0.19
Fenbutatin-oxide 50WP .5 1b 0.25
FUNGICIDES
Bitertanol 50WP .5 1b 0.25
Benomyl 50WP .38 1b 0.19
Captan 50WP 2 1b 1.00
CGA 64251 lOWP .016 lb 0.002
Dodine 65WP .5 lb 0.32
Manzeb+dinocap 80W? 2 lb 1.60
Metiram 80W? 2 1b 1.60
a

b

ICI Formulation

FMC Formulation

RESULTS AND DISCUSSION

I. Life Stage Susceptibility to Azinphosmethyl

A. Egg Susceptibility

 

After assessing the mortality caused by azinphosmethyl

during A; aphidimyza embryonic development, a period of

 

differential susceptibility was found which corresponds to
the latter few hours of egg development. The data collected
in this experiment are presented in Figures 2 and 3. In
Figure 2, percent mortality is plotted against the time of
day the eggs were immersed in the azinphosmethyl solution.
Immersion time is confounded with embryonic age, and Figure
3 is the same data plotted against age of the embryo, with
age zero corresponding to time of oviposition. The points
are scattered, but average mortalities show a peak in
susceptibility between 34 and 44 hours.

Contingency table analysis of total percent mortality
for each cohort (PM and AM) for each date indicates
independence of cohort effects and mortality (Table 4),
both within each date and for the pooled data. However,
comparison of mortalities from DAY I and DAY II shows a
significant difference between days, with DAY II mortality
15.1% greater (Table 5). The effects of tbme of immersion
were tested with the Kruskal-Wallis test (Zar 1974). No

28

29

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mmwm mo 06:. cognac—EH

 

 

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30

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31

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m.me ANN «Hm H see
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paw H%£umamonaa«nm "zuHHMupoE wwm mnaawpfismm .< mo mfim%amnm manna hocmwawucoo .c manmh

 

32
significant differences (P > 0.05) were found in mortalities
among the 3 dip times (Table 6), indicating time of immer-
sion does not affect egg mortality.

Since time of dip has no effect on mortality, the
hypothesis that age of the egg (corresponding to degree of
embryological develOpment) affects mortality was tested.
Two ages are common to each of the four data sets: 12 and
36 hours. Homogeneity is accepted (P > 0.10) for these
results (Table 7), and the contingency table analysis of
the pooled data with subsequent large N produces the con-
clusion that mortality caused by exposure to the azinphos-
methyl LC50 is dependent on the age of the embryo when
immersed. Further tests of egg susceptibility in this
study were conducted with eggs less than 28 hours in age.

Death of A; aphidimyza embryos occurred at or near the

 

time of eclosion irrespective of age when treated, an
observation consistent with the generalized response of
embryos to organophosphates (OP's) reported by Smith and
Salkeld (1966). In their review of ovicidal activities of
pesticides, these authors hypothesized that the mode of
action of OP's involved the delayed action of cholinesterase
inhibition. During normal development acetyl choline and
cholinesterase levels increase as the embryo matures. The
presence of OP's inhibits cholinesterase but acetyl
choline levels do not reach lethal levels until maturation,
when neuromuscular activity increases. Death of less

mature insect embryos is associated with much greater LC50

33

Table 6. Kruskal-Wallis test for effects of time of
immersion in azinphosmethyl on egg mortality in
A; aphidimyza.

 

 

Percent Mortality (Rank)

Time of Immersion

 

 

Cohort 9 am 1 pm 6 pm
ll-l AM 40.5 (11) 42.5 (10) 56.4 (7)
PM 52.8 (9) 58.7 (6) 35.4 (12)
11-17 AM 82.9 (1) 65.4 (3) 56.2 (8)
PM 66.4 (2) 63.7 (4) 61.1 (5)

 

H = 1.038, H0.05,4,4,4 = 5.692; No significant difference.

Table 7. Contingency table analysis of A; aphidimyza egg
‘mortality: azinphosmethyl and age of egg.

 

 

 

 

 

Age Dead Alive % Mortality
12 62 69 47.3
36 103 63 62.0
x2 = 6.43

 

X3 05 1: 3.84; Mortality is not independent of age of egg-

34
values. The mode of action in the early stages probably
differs from that in later stages which have more advanced
development of metabolic and physiological systems; Smith
and Salkeld suggest esterases as the target site in early
embryos.

Embryonic retention of toxin after exposure to pesti-
cides may obscure the relationship between physiological
development and time of exposure. Assessing mortality
after exposing eggs of differing ages to OP's could show
which of the developing systems is most vulnerable to the
toxin, but Smith and Salkeld (1966) found no reports of
differential mortality associated with stages of embryo-
genesis. The results of this study show a period of

greater susceptibility in A;_aphidimyza eggs corresponding

 

to the completion of 70-90% of development. This period
is probably associated with the development of the central

nervous system in A; aphidimyza embryos, evidence which

 

supports the hypothesis of Smith and Salkeld.

B. Comparison of Life Stage Susceptibilities

‘Mortalities for each life stage were assessed with the
1976 source of azinphosmethyl, and results are listed in
Table 8. The mean LCSO values for each stage are presented
in Table 9 with significant differences found between the
first instars and the eggs, second, and third instars
(p < 0.10). Comparison of first instar and adult LCSO
values showed no substantial difference; a high degree of

variation exists in the adult data sets which may be due

35

 

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36

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37

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.m mNan

38
to the difficulty of handling the fragile flies.

To further compare the three instars, the average
weights of the larval sizes subjected to treatment were
determined by weighing two groups of larvae for each in-
star. The ratios of LC50 values and mean weights appear to
be geometric progressions (Table 10), each.with a different
mean (5.2 vs. 2). As larval weight increases, the LCSO
increases but not at the same rate, probably reflecting the
change in surface area and a corresponding change in the
uptake of toxin per unit of weight, or actual dose.

As testing continued from 1979 to 1980 the activity
of the 1976 source of azinphosmethyl seemed to diminish,
and the 1980 source was obtained. Egg and larval stages
were each tested once with the 1980 azinphosmethyl, and
the results (Table 11) show consistent differences when
compared with 1976 means (Table 12). Linear regression on
the two sources explains 91% of the variation in the 1980
source; in subsequent comparisons the 1976 values are
corrected, using the regression equation to approximate
the 1980 susceptibility levels.

The ratios of the LCSO value for each stage to that of
the first instar are listed in Table 12; ratios for each of
the azinphosmethyl sources are approximately equal. Slopes
from the regression lines for each stage have the same rank
for both azinphosmethyl sources, although the slopes for
the 1980 azinphosmethyl are consistently less. The lines

derived from 1980 data are presented in Figure 4.

39

 

 

 

 

 

 

 

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40

Table 12. Comparison of azinphosmethyl sources (1976 vs.
1980) for life stages of A; aphidimyza.

 

 

 

 

 

 

LCSO Ratio
LC50 (stage i/first instar) Slopes
Stage 1976 1980 1976 1980 1976 1980
Egg .0344 .0103 5.9 4.9 3.0 1.6
First .0058 .0021 1.0 1.0 2.1 1.6
Second .0126 .0053 2.2 2.5 2.0 0.8
Third .0240 .0097 4.1 4.6 1.2 2.1

 

Linear Regression of 1980 on 1976 Azinphosmethyl:

Y = .293x + .001

r2 = .91, r = .96

41

 

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42
Mortalities expected in each stage when exposed to the
maximum recommended field rate are predicted by observing
the intersection of each regression line with .03%. First
instar mortality will be greatest, approaching 97%, and
third instar mortality least, about 66%.

These predictions are indicative of the direct toxici-
ties expected after contact with the solution of azinphos-
methyl and its residue, given an adequate food supply,
temperatures between 21-24°C, and high humidity. The
conditions of relatively high humidity and constant food
supply can be expected in Michigan apple orchards through-
out most of the season. Azinphosmethyl causes little
mortality in A;_ppmi, although it has some knockdown effect
(Pielou and Williams 1961b). Sublethal effects and
the indirect toxicity in midge larvae after consuming con-
taminated aphids are not known. Research which addresses
these topics is needed, as are field studies which will
more precisely test the effects of field application of

azinphosmethyl on life stages of A; aphidimyza.

II. Susceptibilities of Field Populations
to Azinphosmethyl

A. Egg Stage

 

The locations of egg collection sites, their classifi-
cations, and the mortalities recorded for each dose tested
are listed in Table 13. Results of probit analysis of

this data are presented in Table 14, and none of the data

43

 

 

 

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44

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45
sets deviates significantly from the regression line
(p > 0.05). The populations are arranged in descending
order of LCSO values. The sites with.no or low probability
of pesticide exposure are nearly separated from the
commercial and research apple orchards. A t-test on the
difference between means of the two groups (C+R, L+N) shows
the means to be significantly different at the .025 level
(Table 15). Ranges of LC95 values overlap at one point
only (.12% a.i.); the group means differ significantly
(p‘: 0.01, Table 15).

Resistance is often recognized as the ability of a
population to survive field rates of the pesticide which
normally kill the majority of susceptible populations.
Additionally, a resistance ratio of 10 or more may indicate
development of resistance in a population. The results of
these tests support the hypothesis that resistance to
azinphosmethyl has developed in some populations of A;

aphidimyza. Although the ratio of maximum to minimum LCSO

 

values is only 3.4 (VerEllen/Heffron), the data collec-
tively represent two groups of populations with different
pesticide exposure histories and differing mean values of
lethal concentrations. Graphical presentation of the
regression lines (Figures 5 and 6) provides further evi-
dence of a low level of resistance development. Expected
mortalities at the recommended field rate in the C+R
populations are all less than 53% and as low as 10% in the

Fennville population, while expected mortalities in the

46

Table 15. Comparison of population means for A. aphidimyza
egg susceptibilities to azinphosmethyl.

 

 

 

 

Population Standard
type Mean deviation Replicates t
mm
C+R .0394 .0119 8 a
2.23
N+L .0272 .0070 6
LC95
C+R .1761 .0788 8 b
2.96
N+L .0868 .0286 6

 

a Significant at a = 0.025.

b Significant at a = 0.010.

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on. 0.. 00. Ho.

 

 

47

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48

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49
N+L populations are generally above 50%, with the exception
of Warren.

FAO (1969) recommends comparing susceptible LC50
values with those from field populations suspected of
resistance development. The most susceptible populations
found are those which have been colonized in the laboratory,
with significant increases in susceptibility occurring
after colonization (Table 16). Errors in correction of the
1976 source of azinphosmethyl could account for some of
the differences, but 1980 source measurements for two of
the colonies indicate the validity of the correction.
Comparing the VerEllen LC50 with the lab LC50 for the
Warren colony yields a 14-fold difference in susceptibility
levels, a ratio indicative of low-level resistance

development in the VerEllen population.

B. First Instar Larvae

 

The field survey of larval susceptibilities was not
as extensive as that for the egg stage. One population
from each type of exposure history was included, with
results presented in Table 17. LC50 values for all but
Rose Lake are considerably greater than that of the Graham
lab colony; regression lines are plotted in Figure 7.
Predicted mortalities for exposure to field rates of the
pesticide indicate no survival for the Rose Lake popula-
tion and 75-82% mortality for the other three populations.

To determine whether the magnitude of difference

between egg and first instar stages is relatively constant,

50

Table 16. Comparison of A; aphidimyza egg LCSO values for
laboratory colonies and field populations.

 

 

 

 

1979* 1980
Population Lab Colony Field Survey Lab Colony
MSU .018 .030 -
Klein .011 .033 -
Anderson .007 .029 -
Graham. .011 .031 .010
Rose Lake .009 .024 -
Warren .004 .039 .005

Paired t-test:
c = 15.64a

 

* Corrected to 1980 azinphosmethyl source.

a Significant at a = 0.01.

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52

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53

the ratios of egg LCSO to larval LCSO for each population
were compared (Table 18). The ratios vary considerably
among the populations, but averaging the two high exposure
and the two low exposure population values yields ratios
which are of similar magnitude, and which are equivalent
to the Graham.lab colony ratio. This information supports
the hypothesis but much more evidence is needed before

generalizing the results.

III. Toxicities of Orchard Pesticides

Differential mortality occurred in the two types of
test chambers used in these experiments. Eight of the
pesticides tested had measures for both chamber types, and
a t-test analysis of mortalities showed a significant
difference between the two chambers (Table 19). Linear
regression of Type II on Type I yielded an equation for
correcting the Type II mortalities to equivalent mortali-
ties for Type I chambers, with 82% of the total variation
in the corrected values explained by the fitted regression.
The following discussion uses these corrected values and
they are indicated by the superscript "*".

The pesticides tested are classified into three
groups:. those causing high mortality (>50%) in both
stages, those causing high.mortality fi>48%) in one stage
only, and those causing low mortality (<30%) in both

stages (Tables 20-22). In the high mortality group, azin-

phosmethyl appears to be the least toxic compound, but the

54

Table 18. Comparison of azinphosmethyl LC50 values for
eggs and first instars of field-collected
é;_aphidimyza.

 

 

 

Population Egg LCSO First Instar LCSO Ratio (Egg/First)

 

Royal .034 .0080 4.2
Graham. .031 .0050 6.2
Rose Lake .024 .0025 9.6
Heffron .018 .0068 2.6
Graham-Lab .010 .0021 4.8

Average Values
C + R .0325 .00650 5.0
L + N .0210 .00465 4.5

 

 

55

Table 19. Comparison of g. aphidimyza third instar
‘mortalities from azinphbsmethyl for two types
of test chambers.

 

 

 

Corrected Percent Mortality

 

 

Compound Type I Type II

Azinphosmethyl 60.3 25.0

Fenvalerate 18.9 13.3

Oxamyl 9.5 23.3

Phosmet 21.4 15.9 Paired t-test:
Dimethoate 86.7 57.4 t = 2.55a
Demeton 78.2 66.7

Endosulfan 83.3 53.3 \

Morestan 6.7 6.7

Linear Regression: Type I Mortality =

1.38 (Type II Mortality) + .56

r2 = .82, r = .91

 

a Significant at a = .05.

56

 

 

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57

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58

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j'J

59
data are from the 1976 source; mortalities caused by the
1980 source will be greater. 0f the stage-selective com-
pounds, five are more ovicidal than larvicidal; only
endosulfan is less toxic to eggs than larvae. Stage
selectivity is significant when a pesticide is applied to

control apple pests; the majority of A; aphidimyza in the

 

favored stage will survive the treatment, allowing for
continued biological control of aphids.

Most of the low mortality pesticides are fungicides
and acaricides but several insecticides could be useful in
an IPM program for aphids. Pirimcarb is an aphicide not
yet registered for use on apples which appears to have no

direct toxic effects on Q; aphidimyza and which could

 

possibly be applied to reduce aphid populations to levels
more favorable for midge control. Carbophenthion provides
good control of San Jose scale, rosy apple aphid, woolly
apple aphid, and white apple leafhopper (Jones, et al.

1980). Phosphamidon provides excellent control of rosy and

“W.w—..._,.+ .

green_apple aphids. ‘fhosalone is recommended for leafroller

and codling moth control while_alsowprOVidihgié°°d ¢°htf°1

of applemmaggot, spotted tentiform leafminer, pest mites,
andfaphids. I

Direct comparison of these results with those of
Adams and Prokopy (1977) is hampered by differences in
dosage and/or formulation. Table 23 lists corrected
mortalities for both data sets. Third instar mortalities

for Massachusetts are generally less than the larval plus

60

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.MN mHan

61
pupal mortalities found in this study, but no trend among
egg mortalities is apparent. Compounds which caused little
egg plus first instar mortality in this study produced
similar low mortalities in the study by Adams and Prokopy.

Low survival of eggs and first instars appears in
both data sets for carbaryl, demeton, and azinphosmethyl.
The Fitchburg population may represent a resistant strain,
especially since the majority of the mortality is from
early instar death, a factor virtually eliminated with the
addition of aphids to test conditions in the present study.
Phosmet and phosphamidon are exceptions to egg mortality
classification. Phosmet results in the present study
varied, with one replicate showing 11% mortality while the
other three had greater than 75% mortality. Phosphamidon
mortality primarily differs by the amount of early larval
mortality in Adams' and Prokopy's work; again, starvation
may be confounding their results.

The results of this study are consistent with other
findings. Markkula et al. (1979b) reported emergence of
adults from treated pupae was unaffected by the fungicides
benomyl and thiram, while diazinon and malathion caused
100% mortality, and.mevinphos and pyrethrin caused
approximately 80% mortality each. Markkula and Tiittanen
(1976) treated second and third instars with acaracides,
finding all six pesticides produced less than 10% mortality,
including oxythioquinox and dicofol, consistent with

results in Table 22. Ovicidal activity of methomyl

62
reported by David et al. (1980) is consistent with the
100% mortality found in this study.

Laboratory reports on the direct toxicities of
pesticides against particular life stages of arthropods are
useful for identification of highly toxic and practically
non-toxic compounds. Results reported here are based on a
single strain reared in the laboratory, and test methods
may not approximate actual exposure in the field. Larvae
on vegetation tend to congregate under aphids and may
avoid direct contact with pesticide spray and with the
residue if aphid colonies are dense. Indirect effects of
pesticides have not been considered here, and consumption
of contaminated aphids may have lethal or sublethal
effects. In addition, food source disruption can occur if
pesticides are applied which are toxic to aphids or are
effective knockdown agents. Although larvae are mobile,
they are restricted to crawling over plant surfaces to
find aphids, and they seem to have limited powers of prey
location. Interspecific and intraspecific competition is
generally not considered in tests of pesticide effects.

In this screening study most of the variables were con-
trolled in order to assess the direct toxic effects of

pesticides on §L_aphidimyza, resulting in information use-

 

ful in initial preparation of integrated pest management

recommendations.

CONCLUSION

Susceptibilities of g; aphidimyza life stages to

 

azinphosmethyl follow the generalization proposed by
Bartlett (1964a), that of adult susceptibility being
greatest, eggs least, and larvae intermediate, if adult
survival after direct exposure to spray is assumed to be
much less than survival after residue exposure. During
embryogenesis maximum susceptibility occurs after 70% of
development is complete, a finding which may shed light on
the mode of action of azinphosmethyl.

Low levels of resistance were found in selected

populations of g; aphidimyza. This might be expected con-

 

sidering the already high levels of tolerance to azin-
phosmethyl, with field mortality not exceeding 90% for

any stage except first instar larvae (Figure 4). Resis-
tance in this species could be diluted easily considering
the dispersal potential of adults. The polyphagous habits
and ubiquitous presence in habitats surrounding orchards
(Harris 1973, Morse unpublished) could produce a constant
influx of susceptible individuals, diluting the resistance
genes and maintaining low levels of resistance in orchard
populations. Furthermore, azinphosmethyl resistance may

be unstable as manifested by the inoreased susceptibility

63

64
of populations after 2 or more generations of laboratory
colonization (Table 16). Many authors (e.g. Keiding 1967)
have noted unstable resistance to organophosphorous com-
pounds in laboratory strains of arthropods. If an unstable,

low level of resistance is present in AL_§phidimyza,

 

elimination of migration of susceptible wild types during
laboratory selection experiments would possibly stabilize
resistance and increase levels substantially.

If the primary mode of action of azinphosmethyl is
inhibition of cholinesterase, as suggested by Smith and
Salkeld (1966), similar levels of resistance might appear
in each life stage; weak evidence for this was found
(Table 17). Resistance to the mode of action of azinphos-
methyl may be present in the embryo, even if selection
pressures are more intense on other stages. After select-

ing larvae of the housefly Musca domestica with

 

diflubenzuron, Grosscurt (1980) found both larvicidal and
ovicidal resistance had developed, though he suggests they
are not linked. The presence and functioning of resis-
tance mechanisms among life stages could provide a basis
for stabilization of resistance in insect species.

Several pesticides with little direct toxicity to A;

aphidimyza have been identified in the survey of pesticide

 

mortalities. All fungicides and most acaricides are
placed in this category, as are several insecticides.
Phosphamidon and carbophenthion are currently registered

on apple as is phosalone, a compound highly toxic to

65
predatory mites and not recommended for use in integrated
mite control in Michigan. Pirimicarb has potential for
reducing aphid populations to levels more favorable for
control by midges, but it is not registered for apples.
The permethrin formulations differed in toxicity to A;

aphidimyza and could be applied without severely disrupting

 

midge populations, but introduction of synthetic pyrethroids
in apple has been discouraged by Croft and Hoyt (1978).
Predatory mites are highly susceptible to these compounds,
and pest mite outbreaks may occur.

Applications of stage-selective compounds would
ensure survival of most individuals in the favored stage,
allowing continuation of biological control within the
orchard. Since egg toxicities are much greater than larval
plus pupal toxicities (except endosulfan), these insecti-
cides do not follow Bartlett's generalization of stage
tolerance in natural enemies. Other factors may determine
life stage susceptibilities, such as pesticide mode of
action, development of detoxification systems, and pene-
tration of toxin. Application of compounds from the high
mortality group should not be recommended unless a large
proportion of the population is pupating, escaping direct
contact with the pesticide.

Adults of AL_aphidimyza do not emerge until June,

 

preventing biological control of early season aphid
populations by this species. Pesticide applications prior

to A; aphidimyza emergence can include compounds highly

 

66
toxic to this midge. Further research which assesses
field toxicities of orchard pesticides to midges and
aphids and combines toxicity information with effective
monitoring for predator:prey ratios will assist in the

implementation of IPM for aphids in apples.

LIST OF REFERENCES

Abbott, W. S. 1925. A method of computing the effective-
ness of an insecticide. J. Econ. Entomol. 18:
265—267.

Adams, R. G. Jr., and R. J. Prokopy. 1977. Apple aphid
control through natural enemies. In: Lord, W. J.
and W. J. Bramlage, eds. Fruit Notes 42: Cooperative
Extension Service, Univ. Mass., 6-10.

. 1980. Aphidoletes aphidimyza (Rondani)
(Diptera: CecidOmyiidae)? an effective predator of
the apple aphid (Homoptera: Aphididae) in
Massachusetts. Protection Ecology 2: 27-39.

 

 

Asquith, D. 1967. Mite and apple aphid control on apple
trees following soil applications of Temik. J. Econ.
Entomol. 60: 817-819.

1970. Codling moth, red-banded leaf roller,
apple aphid, European red mite, and two-spotted spider

‘mite control on apple trees. J. Econ. Entomol. 63:
181-1860

Azab, A. K., M. F. S. Tawfik, and I. I. Ismail. 1965.
Morphology and biology of the aphidophagous midge,
Phenobremia a hidivora Rubsaamen. Bull. Soc. Entomol.
Egypte Z9: ZE-ZS.

 

 

Barnes, H. F. 1929. Call midges (Diptera: Cecidomyiidae)
22 enemies of aphids. Bull. Entomol. Res. 20: 433-
2.

Bartlett, B. R. 1964a. Toxicity of some pesticides to
eggs, larvae, and adults of the green lacewing,
Chrysopa carnea. J. Econ. Entomol. 57: 366-369.

 

. 1964b. Integration of chemical and biological
control. In: P. DeBach, ed. Biological Control of
Insect Pests and Weeds. New York: Reinhold, 844 pp.

 

Blackman, R. L. 1974. Aphids. Ginn. B. Co. Ltd: London,
175 pp.

67

68

Blair, B. D. and C. R. Edwards. 1980. Development and
status of extension integrated pest management pro-
grams in the United States. Bull. Entomol. Soc.
Amer. 26: 363-368.

Bonnemaison, L. 1972. Integrated control of apple orchard
aphids. Abst., Revue de Zoologie Agricole: 48-64.

Brunner, J. F. and A. J. Howitt. 1981. Tree Fruit

Insects. Cooperative Extension Service, Michigan
State University: 96 pp.

Cessac, M. 1963. [Efficacite en plein champ d'un
acaricide nouveau: L'ethion (8.167 R. P.)]. Abstr.,
Phytiat. Phytopharm. 9: 87-94.

Colburn, R. and D. Asquith. 1971. Tolerance of the
stages of Stethorus punctum to selected insecticides
and miticides. J. Econ. Entomol. 64: 1072-1074.

Croft, B. A. 1975. Integrated Control of Apple Mites.

Coop. Ext. Service, Michigan State Univ. Bulletin
E-825 o

, and A. W. A. Brown. 1975. Responses of arthro-
pod natural enemies to insecticides. Ann. Rev.
Entomol. 20: 285-335.

 

, and S. C. Hoyt. 1978. Considerations for the
use of pyrethroid insecticides for deciduous fruit

pest control in the U.S.A. Environmental Entomol. 7:
627-630.

 

, and J. G. Morse. 1979. Recent advances on

pesticide resistance in natural enemies. Entomophaga
24: 3-11.

 

David, P. J., R. L. Horsburgh, J. P. McCaffrey, and L. F.
Ponton. 1980. Apple: the ovicidal effects of
methomyl (Lannate-L) on beneficial insects. Pesti-
cide Research Experiments, Shenandoah Valley Res.
Sta., VA Polytech. Inst. and State Univ.

Elliot, W. M. and M. J. Way. 1968. The action of some
systemic aphicides on the eggs of Anthocoris nemorum

(L.) and A; confusus Reut. Ann. Appl. B161. 62:
215-226.

El Titi, A. 1973. [Influences of prey density and
morphology of the host-plant on the egg distribution
of the aphidophagous gall midge Aphidoletes aphidimyza

(Rond.) (Diptera: Itonididae)]. Abst., 2. Ang.
Entomol. 72: 400-415.

69

Evenhuis, H. H. 1961. Some notes on the dipterous enemies

of aphids harmful for apple growing in Nova Scotia.
Canadian Entomol. 43: 1020-1021.

Food and Agriculture Organization (FAO). 1969. Recommended
methods for the detection and measurement of resistance
of agricultural pests to pesticides. FAO Plant
Protection Bulletin 17: 76-82.

. 1979. Pest resistance to pesticides and crop
loss assessment - 2. Report of the Second Session of
the FAO Panel of Experts, Plant Production and Pro-
tection; Paper 6/2, Rome.

 

Forsythe, H. Y. Jr. 1976. Control of the Rosy Apple Aphid
in Ohio. Ohio Agric. Res. and Dev. Center no.214,
Wooster, Ohio.

, and F. R. Hall. 1973. Summer Control of the
Apple Aphid in Ohio. Research Circular 196, Ohio
Agric. Res. and Dev. Ctr., Wooster, Ohio.

 

Finney, D. J. 1970. Probit Analysis. New York: Cambridge
Univ. Press, 333 pp.

Gagne, R. J. 1971. The genus Aphidoletes Kieffer
(Diptera: Cecidomyiidae) inINorth America. Entomol.
News 82: 177-181.

 

Georghiou, G. P. 1979. The management of insecticide
resistance. Symposium on Pesticide Resistance,
International Congr. of Plant Protection, Washington
D.C.

, and C. E. Taylor. 1976. Pesticide resistance
as an evolutionary phenomenon. Proceedings of XV
International Congress of Entomol., washington D.C.
759-785.

 

. 1977a. Genetic and biological influences in
the evolution of insecticide resistance. J. Econ.
Entomol. 70: 319-323.

 

. 1977b. Operational influences in the evolu-
tion of insecticide resistance. J. Econ. Entomol.
70: 653-658.

 

Gill, J. L. 1978. Design and Analysis of Experiments,
vol. 1. Iowa State University Press: Ames, 409 pp.

Grosscurt, A. C. 1980. Larvicidal and ovicidal resistance
to diflubenzuron in the house fly (Musca domestica).
Proc. K. Akad. Wet. Ser. C Biol.‘Med: Sci. 83: 127-
142.

70

Harris, K. M; 1966. On gall midge genera (Diptera:
Cegidomyiidae). R. Entomol. Soc. Lond. 118: 313-
35 .

. 1973. Aphidophagous Cecidomyiidae (Diptera):
taxonomy, biology, and assessments of field popula-
tions. Bull. Entomol. Res. 63: 305-325.

 

,‘ Holdsworth, R. P. Jr. 1970. Aphids and aphid enemies:

effect of integrated control in an Ohio apple
orchard. J. Econ. Entomol. 63: 530-535.

Jones, A. L., M. E. Whalon, and J. A. Flore, eds. 1980.
The 1980 Fruit Pesticide Handbook. Coop. Ext. Ser.,
Mich. State Univ. Ext. Bull. E-154, 95 pp.

Keiding, J. 1967. Persistence of resistant populations
after the relaxation of the selection pressure.
World Review Of Pest Control 4: 115-130.

Lathrop, F. H. 1928. The biology of apple aphids. The
Ohio Journal of Science 28: 177-204.

Madsen, H. F. and J. B. Bailey. 1959. Control of the
apple aphid and the rosy apple aphid with new spray
chemicals. J. Econ. Entomol. 52: 493-496.

Madsen, H. F., P. H. Westigard, and L. A. Falcon. 1961.
Evaluation of insecticides and sampling methods
against the apple aphid, Aphis pomi. J. Econ. Entomol.
54: 892-894.

Madsen, H. F., H. F. Peters, and J. M. Vakenti. 1975.
Pest management: Experience in six British Columbia
apple orchards. Canadian Entomol. 107: 873-877.

 

Markkula, M., and K. Tiittanen. 1976. Mortality of
Aphidoletes aphidimyza larvae treated with acaricides.
Annales Agric. FEnniae 15: 86-87.

 

, M. Hamalainen, and A. Forsberg. 1979a. The
aphid midge Aphidoletes a hidim za (Diptera,
Cecidomyiidae) afidqits use in o ogical control of
aphids. Ann. Ent. Fenn. 45: 89-98.

 

 

Markkula, M;,'M. Rimpilainen, and K. Tiittanen. 1979b.
Harmfulness of soil treatment with some fungicides
and insecticides to the biological agent Aphidoletes
aphidimyza (Rond.) (Dipt., Cecidomyiidae). Ann.
Agric.7Fenn. 18: 168-170.

 

Matheson, R. 1919. A study of plant lice injuring the
foliage and fruit of the apple. Cornell Agric. Exp.
Sta. Mem. 24: 683-762.

71

Morse, J. G. 1978. Comparative resistance to azinphos-
methyl, in the predatory mite, Amblyseius fallacis,
and its prey, Tetran chus urticae in greenhouse
experiments. . . e813, Mich. State Univ., East
Lansing, MI, 65 pp.

Mullins, W., and E. P. Pieters. 1980. Weight vs. Toxicity:
A Need for Revision of the Standard Method for Testing
Heliothis Resistance of Insecticides. Paper presented
at Ent. Soc. Amer., Dec. 1980, Atlanta GA.

Nakashima, M. J., and B. A. Croft. 1976. Toxicity of
benomyl to the life stages of Amblyseius fallacis.
J. Econ. Entomol. 67: 675-7.

 

National Academy of Sciences (NAS). 1969. Insect Pest
Magagement and Control. Publ. 1695, Washington D.C.,
50 pp.

Newsom, L. 1980. The next rung up the integrated pest
ggnagement ladder. Bull. Entomol. Soc. Amer. 26:
9-37 .

Nijveldt, W. 1969. Gall Midges of Economic Importance.
London: Crosby Lockwood & Son, Ltd, 191 pp.

Oatman, E. R., and E. F. Legner. 1961. Bionomics of the
apple aphid, Aphis pomi, on young, non-bearing apple
trees. J. Econ. Entomol. 54: 1034-1037.

 

Pielou, D. P. and K. Williams. 1961a. The effectiveness
of residues of insecticides in preventing reinfesta-
tion of apple leaves by apple aphid, Aphis omi DeG.

I. Diazinon, Trithion, and Sevin. Cana 1an ntomol.
93: 93-101.

. 1961b. The effectiveness of residues of
insecticides in preventing reinfestation of apple
leaves by apple aphid, A his omi DeG. II. Thiodan
and Guthion. Canadian Entomo . 3: 1036-1040.

 

Prokopy, R. J., W. M. Coli, and R. G. Hislop. 1980.
Sampling methods and provisional economic threshold
levels for major apple insect and mite pests in
Massachusetts. In: 'W. J. Lord and W. J. Bramlage,
eds. Fruit Notes 45: 15-18.

Rettich, F. 1980. Field evaluation of permethrin and
decamethrin against mosquito larvae and pupae (Aedes
cantans). Acta Entomol. Bohemslov 77: 89-96.

Sell, P. 1976. [Monogeny in Aphidoletes aphidimyza
(Rond.)]. A. Ang. Entomol. 82: 58-61.

72

Singh, 0. P., and R. R. Rawat. 1980. Toxicity of some
insecticides against pupae and adults of Dicladispa

armi era (Coleoptera: Chrysomelidae) on rice (Oryza
sativa). Indian J. Agric. Sci. 50: 271-272.

 

Smith, E. H. and E. H. Salkeld. 1966. The use and action
of ovicides. Ann. Rev. Entomol. 11: 331-356.

Specht, H. B. 1972. The apple aphid A his pomi (Homoptera:
Aphididae) on apple under summer con itions in a
controlled environment cabinet. Canadian Entomol.
104: 105-111.

Streibert, H. P. and V. Dittrich. 1977. Toxicological
response of insect eggs and larvae to a saturated
atmosphere of chlordimeform. J. Econ. Entomol. 70:
57-59.

Westigard, P. H. and H. F. Madsen. 1965. Studies on the
bionomics of summer generations in California of the
apple aphid, A his omi DeGeer (Homoptera: Aphididae).
Canadian Entomol. 9 : 1107-1114.

Zar, J. H. 1974. Biostatistical Analysis. New Jersey:
Prentice-Hall, Inc., 620 pp.