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RESFONSE 0F APPLE VARIETIES TO MITE
INFESTA‘HON ANS) THE STATUS OF GRQHARD
MITES RESISTANCE T0 CRGANSPHGSPHORGGS
COMPOUNDS 3N 500?.‘i‘e ’fiS‘EERN MiCHIGAN

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MK‘HIGAN STATE UNIVERSRTY
Ashok V1953! Ghate
1962:

 

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RQSEONSJ 0F AIPLE VARIETILS TO MITJ INFESTATION
AKD TEL STATUS OF ORCHARD HITS; RESISTANCE
TO ORGAHOIHOSIJQRQUS COHEUUKLS IN
SOUTHWES th MICHIGAN.

by Ashok Vithal Ghate

Mite counts from 8 apple varieties were made to
study the response of apple varieties to mite infestations.
Bioassay tests were carried out on European red mites,
Panonychus ulmi (Koch), and two-spotted spider mites,
Tetranychus telarius (L.) to determine the susceptibility of
the orchard mites from different orchards in southwestern
Michigan, to parathion and malathion. Bioassay tests were
made to determine the effectiveness of Kelthane on parathion
resistant two-spotted spider mites. The results of the
experiments are outlined as follows:

1) Mite populations were highest on the Red Delicious
variety. Yellow Transparent, Grimes Golden and
Jonathan varieties were more susceptible to mites
than Wagener, McIntosh, Wealthy and Dutchess.
Maximum clover mite populations were evident on
the Yellow Transparent variety.

2) Resistance to parathion and malathion was evident
with the SurOpean red mites. The level of resistance
to malathion was slightly higher than to parathion.

A strain from Eau Clainzon plum and a strain from

3)

4)

5)

6)

7)

Bangor on apple showed a 22 fold and a 21 fold
increase in LD 50 to parathion and a 50 fold and

a 13 fold increase in LD 50 to malafihion over a
susceptible strain. A strain of EurOpean red mites
collected from Eau Claireon cherries was most
susceptible to parathion and malathion.

Clover mites were highly susceptible to both parathion
and malathion. Clover mite pOpulations were more
homogenous in, their reSponse to parathion and
malathion than EurOpean red mite populations.
Two-spotted spider mites also showed evidence of
resistance to parathion, however the level of
resistance was not high. A strain from Sparta on
apples showed a 9 fold increase in LD 50 over a
susceptible strain.

A susceptible strain of two-spotted spider mite
collected from red clover and maintained in the
greenhouse on beans did not lose it's susceptibility
to parathion after two years.

Parathion-resistant two-spotted Spider mites were
easily controlled with Kelthane.

Resistance of EurOpean red and two-spotted spider
mites to parathion and malsthion has developed due to
the frequent applications of various organophosphorous

pesticides.

Rnsrowst or APPLL VinItrIss T0 MITE IRFJSTATION
AND THE STATUS or OhCHARD hirES RLSISTANCE
TO OAGANOPHOSIHQRQUS CQ;POJNUS IN
SOUTHWESTERN MICHIGAN

By
Ashok Vithal Ghate

A TflESIS

Submitted to the College of Science and Arts,
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIBECB
Department of Entomology

1962

ACKNOWLEDGMENTS

My grateful acknowledgment is made to Professor
Ray Hutson, Head of the Department of Entomology, for

providing the assistantship which made this study possible.

To Dr. Angus Howitt, under whose guidance this
investigation was made, I wish to express special thanks

for his constant interest and assistance.

My sincere appreciation is extended to Dr. Wayne
Woodby, the superintendent of schools and Mr. William
Gleason, Vocational Agriculture Teacher, Fennville High
School, Fennville for use of the facilities of the Vocational

Agriculture Building for fiiis research.

I wish to express my thanks to Dr. Roger
Hoopingarner for his assistance with the figures and

suggestions.

I also wish to extend my sincere appreciation to
Doctors G.Guyer, E.S.Beneke and Mr.Arthur Wells for their

critical reading of the manuscript.

ii

II
III

IV

VI

TABL: or oongNTs

Introduction...................................
Literature Review..............................
Procedure......................................
Part A

Experiment I..............................

Experiment II.............................

Experiment III............................
Part B

Experiment I.............................L
Presentation and Discussion of Results.........

SmaryOOOOOOOOO00.0.00...OOOOOOOOOOOOOOOOOOOOO

BibliographyOOOOOOOO0.00000000000000000000COOOC

iii

Page

12

12
14
17

19
22
42
46

Table

1.

3.

5.

LIST OF TiELhS
Page

Response of orchard mite populations to
different varieties of apple................ 23

Laboratory studies showing the effects of
parathion sprays on strains of the European

red mite collected from different areas of
Southwestern Michigan, 1961................ 25

Laboratory studies showing the effects of
malathion sprays on strains of the European

red mite collected from different areas of
Southwestern Michigan, l961............... 31

Laboratory studies on the effects of
parathion and malathion sprays on strains of

Clover miteSOOOOOOOOOOOOOOOOOOOQOOOOOOOOOO 34

Laboratory studies on the effects of parathion
and Kelthane sprays on strains of

two-spotted spider mites collected from
different areas of Southwestern Michigan,

1961000000000000000000000000000000000.0000. 38

iv

Figure

I.

2.

3.

LIST OF FIGURSS

Dosage-mortality curves of Panonychus ulmi

(Koch) in response to parathion.............. 26

Dosage-mortality

curves of Panonychus ulmi

(Koch) in response to malathion.............. 32

Dosage-mortality
Koch in response

Dosage-mortality
(L.) in response
Dosage-mortality
(L.) in response

curves of Bryobia praetiosa
to parathion and malathion.. 35

curves oi Tetranychus telarius
t0 parathionoooooooo00000000 39

curves of Tetranychus telarius
to Kelthwe00000000000000... 4O

INTRODUCTION

Resistance of orchard mites to acaricides is a serious
problem in the United States and other countries. O'Neill
and Hantsbarger (1951) were the first to report European red
mite resistance to parathion and several other phosphate
compounds in apple orchards in the Wenatchee Valley of
Washington. Now most of the apple infesting mites have
develOped resistance to parathion, TBPP, malathion and other
organophosphate acaricides wherever these materials have
been used regularly in the spray program. The EurOpean red
mite Panonychus ulmi (Koch), two-spotted spider mite,
Tetranychus telarius (L.), pacific mite Tetranychus pacificus
McG., four Spotted spider mite T.canadensis (McG.), McDaniel
mite 2.Mcdanieli McG. have been reported resistant to at least
one of these materials. The European red mite is also known
to be resistant to ovex (Foott 1959), chlorobenside, fenson,
Genite and Chlorobenzilate in apple orchards.

Madsen (1958) stated that resistant strains existed in
California for all summer Sprays on pears except with Tedion
and Sulphenone. The EurOpean red mite and two-spotted spider
mite are resistant to parathion on peaches and plums in 9
states of United states and Canada. EurOpean red mites have
been in America for half a century and are now widely
distributed over the country. They were first observed in

United States by Dr.H.L.Ewing in Oregon in 191L(WEbster 1949)-

-1-

-2-

In Michigan, European red mites and two-spotted spider
mites are serious economic pests. The clover mite Bryobia
praetiosa Koch also occurs in Micnigan but is not as
serious a pest as Paglgi (Koch) and T.telarius (L.).
burepean red mites and clover mites overwinter as small red
eggs on twigs and tree branches. Adults of the European red
mite can be identified by their red color and stiff spines
protruding from their backs. Clover mites lack the spines
and their front legs are twice as long as the other legs.
Two—spotted spider mites overwinter chiefly in the adult
stage and are ordinarily not present in serious numbers until
July. They are one of the most important pests of greenhouses.

In Michigan, mite resistance has not been a Serious
problem. Mitchell (1952) reported that European red and
twoespotted spider mites could readily be controlled with
numerous organic miticides. Sherman(l955) reported that
mites had developed resistance in greenhouses but not in
orchards. Parathion and other organophosphates had still
given good control of mites when used in spray programs.
iaines (1958) stated that sites were resistant to parathion
in orchards. He reported that control was obtained by the use
of an early treatment followed by mid—summer applications of
miticides. Kelthane was the most effective compound evaluated
for control of the mites.

The objectives of the investigations reported here were:

1) To study the response of apple varieties to mite

infestation.

-3-

2) To determine by laboratory technique if there is
resistance of European red mite, two-spotted spider
mite and clover mite from orchards, to parathion and
malathion.

3) To determine the effectiveness of Kelthane for control

of two-spotted spider mites.

LITDRATURE REVIEW

Resistance is interpreted by Glass (1960) as a greater
tolerance for a pesticide than that possessed by the normal
or original strain of the pest. The matter of resistance of
insects or mites to insecticides is not new. It was recognized
sixty years ago and since then 18 resistant strains of insects
and mites are known to exist on deciduous orchard trees and
Vines (Glass 1960). Dr. Melander recognized the resistance of
San Jose scale to lime sulfur in the Clarkston, Washington
area fifty years ago. The resistance of the red scale on
citrus in California to hydrogen cyanide has been well known.

On apples resistance of codling moth Carpocapsa pomonella (L.)

 

to lead arSenate in some degree is universally known. More
recently this insect has become resistant to DDT and certain
other chlorinated hydrocarbons, in some of the major apple
growing regions of the United States. The red-banded leaf
roller Argyrotaenia velutinana (Wlk.) has become resistant to
TDE in many orchards in the Eastern parts of North America.
It is not surprising therefore that similiar resistance
should develOp in orchard mites.

March (1958) reported that little is known concerning
the biochemical mechanisms of mite resistance to organo-
phosphate compounds. However, Taylor and Smith (1956) have
studied the organephosphorous resistance in Tetranychus
telarius (L.) and T.cinnabarinus.BoiSduval by means of

diagnostic dosages of malathion and found it to be inherited

-4-'

-5-
as a single dominant factor.

Andres and Prout (1960) also provided evidence of a
major gene for resistance. In 1937 it was found that the
two-spotted spider mite, Tetranychus telarius (L.) on roses
in certain greenhouse in Illinois were more difficult to kill
with selenium and certain sulfur compounds,than were mites on
snapdragons and other flowering plants. In 1959, in Ohio
two-spotted spider mites on roses were less susceptible to
acaricides than when they were on beans or tomatoes (Newcomer
1951). Neiswander and Morris (1940) first suggested the
possibility of mite resistance to selenium.

Parathion was introduced in the United States in 1947
and was widely and effectively used to control orchard pests
including mites. Sherman and King (1948) reported outstanding
control of the two-Spotted mite in Eichigan when parathion was
used as a summer spray. In Missouri, Wingo and Thomas (1948)
obtained good control of mites on soybeans. In the pacific
Northwest, Newcomer and Dean (1948) found parathion to be of
great promise against BurOpean red nite and pacific mite,
Tetranychus pacificus McG. In western New York, Chapman and
Lienk (1950) recomended parathion and TEPP for the control
of European red mite.

Asquith (1950), Baker (1952), Lienk and Chapman (1951),
Hough (1948) and Chapman (1955), reported good control of
orchard mites with parathion, TEPP and Aramite. Madsen and
Bailey (1959),Haines (1957). Foott,g§ Q; (1959) reported

good control of orchard mites with Guthion. In Canada

~6-
outstandiig results were obtained in laboratory work
conducted on mites at Nova Scotia, Quebec, Ontario and
British Columbia with CPR and demeton.

Aerosol containing parathion was found better than
aerosol containing hexaethyl tetraphosphate and was recomended
for the control of pests of greenhouse including two-spotted
spider mites (Smith,gt g1,1948, Blauvelt and Hoffman 1948).
Jacks (1954) reported effective control of T.urticae Koch
on beans in the greenhouse with .0005 percent parathion.
Rosenstiel (1948) obtained 94 percent control of two-Spotted
spider mites on beans in the greenhouse. In 1948, strains of
two—spotted spider mites resistant to aerosols of parathion
were found in greenhouse in Maryland, New Jersey and
Connecticut (Smith and Fulton 1951). These strains were also
studied by Hamilton (1950) and the resistance was reported
to carry over into succeeding generations. The resistance was
not lost when the mites were grown on ornamentals, weeds
and food crOps (Smith 1951). Two-Spotted spider mite resistance
was also reported by Garman (1950) in the greenhouse. In
Norway, greenhouse spider mite T.urticae Koch was reported
to be resistant to parathion,(Fjelddalen and Daviknes 1952).

There is both a natural and an induced variation in
two-spotted mite pepulations. Neiswander, gt Q; (1950)
observed that two-spotted spider mites of green type were
much more resistant to the action of acaricides than the
two-spotted spider mites of red or maroon type and the mite

pepulation feeding on roses was usually more resistant to

-7-
the action of acaricides than the mites on beans.

Most of the apple infesting mites have deveIOped
resistance to parathion, TEPP, malathion and other phosphate
acaricides whenever tiese materials have been used regularly
in the spray program. Watson and Naegele (1960) studied the
influence of selection pressure on the development of
resistance in populations of T.telarius(L.) by deve10ping
strains of the two-spotted spider mite resistant to parathion
under 96>F. constant temperature carried through forty-five
generations and found that resistance developed more rapidly
under high selection pressure, Under regular periodic
selection the same level of resistance was reached in time
regardless of selection pressure. High levels of resistance
were demonstrated after a Single severe selection.

O'Neill and Hantsbarger (1951) reported that a strain
of European red mite in the Wenatchee Valley of Washington
was resistant to parathion and several other organephosphorous
compounds including BPN and TLPP. No resistance was found
to be present to non-phOSphorous compounds. In 1951 phosphate-
resistant mites were found in the Yakima valley. Newcomer
(1951), Newcomer and Dean (1952,1953) reported that repeated
applications of parathion caused P.313i,i.pacificus,
T.Mcdanieli to become resistant to this compound. Newcomer
(1951) suggested the use of two or more materials with
a different mode of action during the season to prevent
resistance. He reported that EurOpean red mites had not

developed resistance to oil.

-8—

In hichigan the problem of mite resistance was
restricted to greenhouses and was not believed to be an
important factor in their control in 1953, (Sherman 1955).
Cutright (1955) reported that experimental work conducted
in 1955 demonstrated that nites were resistant to parathion.
hence limited use of parathion was advised in Ohio. Outright
(1958) also reported two races of parathion resistant mites
in northern Ohio. One population was not resistant when
demeton was used for control whereas the other immediately
became resistant to demeton. In a three year field study
of parathion-resistant Burcpean red mites, Outright (1956)
reported that the cessation of the use of parathion for one
season did not reduce resistance. However parathion became
effective again after its use was discontinued for two
successive years.

In southern and central Net Jersey reports were received
in August 1951 that parathion was not giving satisfactory
results at the recomended dosage. Experiments showed the
develOpment of resistance of European red mites to parathion
and TEPP (Driggers 1954). hamilton (1950) reported orchard
mites developing resistance to parathion. Dean (1956)
reported that P.21mi had become resistant to TEPP and
malathion, but that demeton still gave effective control.
Harris (1955) reported that EurOpean rod mites had develOped
resistance to parathion.

Lienk 23 El (1952) reported that nuropean red mites

had become resistant to parathion and malathion in New York.

-9-
This strain was however highly susceptible to Aramite. In
Eastern New York Lienk (1955) reported orchard mites resistant
to organophosphorous compounds.
In California, Eadsen and Bailey (1959) reported that

resistant strains are known for all summer acaricides

except Tedion, and Sulphenone. The development of resistance
to acaricides by the EurOpean red mite on pears in California
parallels the situation on apples. Resistance to the ovex
group and Kelthane is limited to a few orchards.

Resistance of orchard mites to chemicals has been

reported outside of United States. Strains of EurOpean

red mites resistant to parathion, malathion and systemic
organephOSphates, in British Columbia, Canada, have been
reported by Downing (1954,1959). Foott (1959) found

EurOpean red mite resistant to ovex and related compounds

in Ontario, Canada. In Norway greenhouse spider mites
T.urticae Koch have developed resistance to parathion,
(Fjelddalen and Daviknes 1952).Van de Vrie, (1959) observed
the resistance of Panonychus ulmi (Koch) to organephosphorous
insecticides, in Zeeland, Holland. In South Africa, two-
spotted spider mites were reported resistant to parathion,
(Kriegler 1957). There are also recent reports of resistance
of orchard mites to organophosphorus compounds in South
Australia, England, Israel, Japan, Syria, Tasmania (Glass
1960, Brown 1961).

Control 9; organophosphorous resistant mipgg.

Newcomer (1951) suggested that if the continued use of

-10-

a single acaricide such as parathion tends to build up resistance
then it is better to use two or more different materials

during the season. Asquith (1960) suggested using a mixture

of two acaricides each having different chemical properties.
Outright (1956) reported that mites gradually lose their
resistance to a specific chemical when other chemicals with
different killing actions are used, However, Crow (1957)
reported that a snort period of absence of the insecticide

is not likely to lead to a susceptible population. A susceptible
population that has once been resistant is likely to increase
rapidly in resistance when the specific chemical is again
applied (Keiding 1959, Crow 1957). Pimentel (1954) also

reported that reversion of resistance arising in the field

is less likely than among laboratory populations. Aramite

was still effective against parathion resistant orchard mites
according to (Newcomer and Dean, 1953, Lienk 23 31 1952,
Hamilton 1950, Lienk 1955, Cutright 1956, Driggers 1954 and
Naegele 1955).

Another outstanding material for the control of organe-
phoSphorous—resistant mites is Kelthane. It is a Specific
miticide-that has performed well in Michigan during the past
six years (Mitchell, Dowdy and Klos 1961). Many other workers
reported excellent results in controlling mites with Kelthane,
(Van de Vrie 1959, Foott gt 3; 1959, Chapman 1959, 0atman1959,

Haines 1958, Naegele 1956, Nistric 1957, Ellertson 1960).
Naegele (1956) reported that Kelthane was most effective

against phosphate resistant strains of two-spotted mites.

-11-
Other promising acaricides regorted are Tedion, demeton,
ethion, ovex and Trithion.

European red mites on apples have been reported to be
resistant to one or more of the following compounds-
fenson, Genite, chlorobenside and Chlorobenzilate (Collyer
and Kirby 1959, Outright 1956, Foott gt a1 1959, Madsen
1958, hadsen and Bailey 1959, Newcomer and Dean 1952,1955,
Van de Vrie 1959.).

In New York and in certain other areas the European
red mites and two-spotted mites on peaches have develOped

resistance to parathion.

”RUCnDURS
Part A.

All work reported in this section of the study was conducted
in the Vocational Agricultural Building of the Fennville
High School located in Fennville,Michigan. These experiments
were carried out during July, August and up to the middle of
September 1961. Fennville was selected since it is centrally
located to the fruit growing areas of southwestern Michigan.
In addition an experimental orchard developed by the Lakeland
Fruit Growers Incorporated, was located in the Fennville area.
The Superintendent of Schools, Dr.Wayne Woodby, cooperated by
allowing personnel associated with entomological research to
use the facilities of the Vocational Agriculture Building.
Experiment I

The purpose of this experiment was to study the response
of apple varieties to mite infestations. The experimental
orchard at Fennville was selected for this study. The orchard
had been unsprayed for the past two years. Bight apple
varieties were selected for the mite pooulation study. Four
trees (replicates) of each variety were selected at random
for mite counts. It was found that the border trees were
more heavily infested with mites than the trees in the center.
Hence one tree from each variety at the border was selected
from the middle of the orchard. Leaves were collected for
examination around the periphery of each tree. A sample of
100 leaves equally divided among the four replications was

-12-

-13-

taken at random at shoulder height and at arms length from
each variety or treatment . The leaves were placed in quart
ice cream cartons, marked according to treatment and taken

to the_Vocational Agriculture Building, Fennville High School.
Upon arrival,the samples were refrigerated at 46156 F. to
permit delayed counting.

Mites and eggs were removed from the leaves to glass
plates with a brushing machine (Henderson and McBurnie 1943,
Morgan gt g; 1955).The plates were normally examined immediately
but sometimes were refrigerated overnight. Henderson and
Mchurnie (1943) found that the machine re:oved 82 percent of
the eggs and 88 percent of the active stages of the citrus
red mite from orange tree foliage. Morgan 33 a; (1955) found
100 percent of the active stages and 98.8 percent of the eggs
of the durOQean red mite and of clover mite were removed from
leaves of Delicious apple trees. The apparatus consists of a
small electric motor that drives two contrarotating spiral
brushes and a turntable mounted about six inches below. An
adhesive coated glass disk, five inches in diameter, is
placed on the turntable to trap the mites. The machine is
Operated by inserting the leaf between the whirling brushes
and withdrawing it, first one end of the leaf is brushed and
then the other. To prevent the mites from being thrown out
beyond the disk, a pair of curved metal slides extend about
two inches above the brushes and down to within one-eight
of an inch of the revolving disk. A binocular micros00pe

was used in counting mites on the plates. The total plate-

-14-
area consisting of 20 sectors of the counting disk was examined.
If the number was more than 200 then only half the counting
disk consisting of 10 sectors was counted.

The apple varieties selected for mite count were Red
Delicious, Wealthy, Grimes Golden, McIntosch, Yellow Transparent,
Jonathan, Wagener and Dutchess. The mite counts were taken on
August 12, 20,27 and September 5,1961.
ixperiments ll,lll

The purpose of these experiments was to determine the
susceptibility of huropean red mites, and clover mites from
different orchards in Nichigan to the organOphosphates,
parathion and malathion. Technical grades of parathion and
malathion were employed for testing.

Experiment 1;

The European red mite was used as the test mite in the
laboratory studies, concerning the organOphosphorous compounds,
parathion and malathion. Mites from apple,prune and cherry
orchards were collected from Fennville, Paw-Paw, Eau Claire,
Coloma and Bangor.

The leaves were examined by means of a magnifying lens
for file presence of European red mite.The heavily infested
leaves were brought in paper bags or ice cream cartons to
the Vocational Agriculture Euilding of Fennville High School,
Fennville for testing. If distant orchards were involved
cartons or paper bags were transported in an insulated ice-chest.
Upon arrival at the laboratory the samples were refrigerated

at 45:56’F. Regrigeration permited a delay in testing for

-15-

at least three days. Generally when the mites were brought
from the orchards they were treated on the same day in the
laboratory to measure their resistance to parathion and
malathion.

One percent stock solutions of parathion and malathion
were made in acetone and were stored in 100 ml. flasks
securely stOppered in a refrigerator at 46:56)F. One percent
solutions of parathion and malathion were used for further
dilutions for one week after which new stock solutions were
made and the old ones discarded. All solutions were made in
acetone. A Spreader, Vatsol (10 percent) was added with an eye
dropper until even wetting of the leaves was obtained. The
sprays were thoroughly mixed with a glass stirring rod.
Bioassay Eggtg

A modification of the leaf disc method as described by
Rodriguez (1958), and Hoyt and Harries (1961) was used to
test the mites. Selected leaves were dipped and evenly
wetted in the spray mixtures. After the spray dried, discs
thirteen-sixteenths of an inch in diameter were cut from
the leaves with a cork borer. A streak of vaseline was
applied to the cut edge of each disc, by rolling the discs
on a glass slab smeared with a thin coat of vaseline. Tests
showed that mites were repelled by a vaseline barrier at the
edge of the leaf disc. The leaf discs were placed with the
upper side down on slightly larger disc (1 inch diameter)
of white blotting paper and the mites were placed on the

lower side of the leaf discs. These were put on cellulose

-15-

sponge pads 3 inches in diameter and one-half inch thick in
lOOmv. petri dishes partially filled with water. Five discs
or replicates were placed in each petri dish after which
each disc was infested with 10 adult mites from selected
leaves brought from the orchards. The mites were moved to the
discs with a brush made by keeping a single fine hair to the
end of a wooden handle.

dites from apple cherry and plum trees were tested on
discs from bean leaves since it was found that leaf disks
from cherry, plum or apples did not have a waxy surface nor
were they flat and thin enough to rest evenly flat on the
moist blotting paper. It was also found that the leaf discs
from apple, cherry or plum tended to get moist on the upper
surface drowning the mites sometimes. Dark red kidney bean
(Phaseolus vulgaris L.) was used for making leaf disks. The
petri diShes were left uncovered at room temperature of about
7§,F. Three fluorescent tubes were installed over the table
containing petri dishes to furnish the light required to
maintain l4 tolS hours photoperiod. The fluorescent tubes
were covered with a green paper to produce a subdued light.
It was noted that in the presence of subdued light the mites
had less tendency to move to the moist barrier. European red
mite counts were made using a binocular micrOSCOpe and counters
for recording the living and dead mites. Counts were made at
intervals of 24 hours and 72 hours. Mortalities were computed
using Abbott's formula to correct for natural mortality and

build up of the check as related to populations (Abbott 1925).

-17-

The LD-SOs were determincd from 72 hours count.Dosage against
percent mortality were plotted on logarithmic probability
paper (No.3128,Codex Sock Co.,Inc.,Norwood, Mass.). With a
tranSparent strainght edge a temporary straight line through
the points, particularly those in the region of 40 to 60
percent effect was fitted. The Chiztest was adOpted to see
the fitness of the line. The slope function (3), LD 50s with
19/20 confidence limits were determined by the method of
Litchfield and Wilcoxon (1949).

Experiment III

 

The clover mite, was used as the test mite in laboratory
studies concerning the organOphOSphorous compounds, parathion
and malathion. Unfortunately only two strains of clover mites
could be collected from apple orchards and one strain from
sour cherries indicating that clover mites are seldom troublesome
as fruit pests in well sprayed plantings in Michigan.

Clover mites were collected from apple and cherry trees
using the methods previously described. However it was found
that the clover mites prefer the Yellow Transparent variety of
apple and both the strains of clover mites on apple were found
on Yellow Transparent.

The method used for Bioassay tests was the same as in
EXperiment.II with some nodifications.The petri dishes
containing five leaf discs with adult mites were enclosed by
a rectangular cage(52§(28“x24") covered with an inert vinyl
plastic, Snetsinger (1956) reported that temperature of 663F.

O
to 70 F., with relative humidities of 90 percent were the most

-l8-
satisfactory ones for incubation and rearing of clover mites.
The plastic cage was filled with 3 inches of moist Sphagnum

mo

69

s to serve as a moist chamber and the petri dishes were

.‘._J

r

"(1

e t on the Sphagnum moss. Water was added daily to the Sphagnum
moss to keep it moist. The petri dish covers were propped
Open to a width of 2 mm. to prevent fogging of the inside of
the covers and resultant moisture drops on the discs.
Clover mite counts were made using the methods
previously described. LD 50s with 19/20 confidence limits

were determined by the method of Litchfield and Wilcoxon

(1949) previously described.

Part B

The experiments in this part were conducted at the
Michigan State University Plant Science greenhouse,
Entomological section located at East Lansing, Nichigan.
Experiment I

Two-Spotted Spider mites, were used in this investigation.
The purpose of this experiment was to conduct bioassay studies
on 5 strains of two-spotted spider mites collected from apple
orchards and one strain of two-Spotted spider mite reared
in the greenhouse for two years. A 15 percent wettable
powder formulation of parathion was employed in this work.
Method of rearing and testing

A modification of the method as described by Cleveland
(1960), Andres and Reynolds (1958) was used for rearing and
testing the mites. The temperature was maintained at 75’F.

f 10, and relative humidity over 60 percent.

The cranberry beans were grown in 4 inch pots. Plants
were watered lightly every day, but no nutrients were added.
Two pots of plants were kept in white enamel trays. To
prevent migration of mites, the trays contained about one
inch of water. As soon as the plants began to vine, the
vines were cut. It was seen that the loaves did not touch
the ground or any other material. The trays containing the
pots were enclosed separately by a rectangular cage (52"x
28hx24") covered with an inert vinyl plastic. A door at

one side of the cage permitted access to the colonies of mites.

-19-

-20-

Fresh bean plants were added at the first Sign of plant break
down. Mites were transferred from one plant to another by
removing the old mite-infested leaves and placing them on

the new plants. In this way 5 colonies of two-spotted spider
mites from orchards and one colony of greenhouse strain of
two-spotted spider mites were maintained.

Four beaneseeds were planted in each pot. The seeds
germinated in about 5 to 6 days. When the plants were 5 to 4
inches tall they were infested with mites. A section of a leaf
from a stock plant heavily infested with mites— eggs, adults
and nymphs was placed on each leaf of the test plants 2 to 5 days
before treatment to give time for the build up of a good
infestation.

Treatments: Four plants were used for each treatment. The
sprays were tested at different dosages. Distilled water was
used in mixing the sprays. The sprays were thoroughly mixed
and were constantly stirred with an magnetic mixer while being
used. Spray treatments were applied in a ventilated booth
using a specially constructed atomizer while being rotated
on a turntable. The atomizer was mounted about 20 inches
from the plant.

Counts: Mortality counts of adult mites were made 24 hours
and 72 hours after treatment. The percent mortality was
based on the total number of dead and live adult mites
present on the leaves. Two leaves from each plant were

taken for counting. Counts were made using aéépencer

binocular wide angle microscope, and counters for recording

-21-
the living and dead mites. The leaves were observed for mite
count by keeping under a 7 mm. square counting grid for
keeping track of the mites. About 25 to 50 mites per
replication (two leaves) were counted depending upon the

infestation of the mites.

PRESENTATION AND DISCUSSION OF RESULTS.
' PART A
Experimentg;

The data from part A of experiment I is presented in
Table l. Mite populations were found to be the highest in
the Red Delicious variety. Yellow Transparent , Grimes Golden
and Jonathan varieties were also found to be more susceptible
to mites when compared with Wagener, McIntosh, Wealthy and
Dutchess. Eur0pean red mite and two-Spotted mite pOpulations
were found to be maximum on Red Delicious variety. Grimes
Golden and Jonathan were also susceptible to Surcpean red
mites. Clover mite pOpulationS were maximum on Yellow
Transparent. The results indicated that two-Spotted mites
were very scarce in this orchard and negligible. Due to the
rains on September 5 and the beginning of cold weather mite
pOpulations were greatly reduced by September 6,1961.

After surveying many orchards of apple and pears it
was found that EurOpean red mite populations were beginning
to build up about the middle of June. Many orchard growers
reported the presence of European red mites chiefly on Red
Delicious, Jonathan and Grimes Golden. No reports were
heard about two-spotted spider mites till the middle of
August 1961. Two-spotted Spider mites caused little damage
in orchards in 1961. Reports from different sections of
Michigan indicated that populations of this pest were low
throughout the season. EurOpean red mites were more abundant,

-22-

-23-

 

 

HHm oe Hem emH one we owe sea was He Has eeH wee em awn HHH meoHoHHos eoe
e o e oH Hm e mH em mm o A HH as o e e muoeose
MNH H HHH as sea NH esH oeN meH m oeH emH HRH o eNH HHH eoeHoe moeHue
HwH c He mam ooe e meH oem eem e eoH HmN New H as sea .eueeus 3oHHo»
as m ow e NNH oH meH mH eHH a HeH e me a NmH e eesoeeos
mm 0 mm em eoH m soH ee as H as HN an 0 He mH seoHeoz
ee 0 He HN ms H HHH me as N mm em ee 0 en HH euooeHoz
me o HN om mHH o as meH ea 0 Ne HeH as o om we toeowez
H _L .d, 48 3 LL 4d ,l4fl 3 #1 _d ‘43 3 41 _d 49
WW . o 0 mm o o o % . o - mm o . o kh
S .4 n S 3 n S 1. n S .4 n u o H Hm>
3 TL 1 a T. 1 a T. 1 a .L J
T. m e T. m 9 TL m e .L m B
B T. a B T.. a B I. a E I. a
J 1 1 3 1 3 1 3
T.- _.Lc T... T: T.- _.L. TL. I.
n O n O n O n O
S S S S S S S S
E B E B
HeeH .m toesooeom HeeH .AN outwe< HeeH .oN ouswss HeeH .NH senses

 

mo>moH OOH Hod wwwm was mouHE mo HmnESZ

 

 

.mfimam mo mowuofinm> acouowmfip ou mcowumadaoa mafia wumsouo mo omsoamom .H oHan

-24-
particularly on plums and apples.
Experiment II

The results of the bioassay tests on European red mites

with parathion are given in Table 2. Figure 1 shows the
dosage mortality curves of 15 strains of huropean red mites
plotted on logarithmic probability.paper. From this the LD
50 which is an index of the mean tolerance or the mean
resistance of the group tested is determined with their
confidence limits using the method described by Litchfield

and Wilcoxon (1949). From the Chi tests for detecting a
poorly fitted line or Significantly heterogenous data, it

was found that the data were not significantly heterogenous
and the lines were a good fit. From the mortality curves
(Figure 1) it is apparent that the European red mites are
becoming resistant to parathion. The results do not show
marked differences in the LD 50s for different strains.

The level of resistance ranged from 2 to 22 fold over the
least resistant strain H, which was collected from Eau Claire
on CherrX.Strain A, which was collected from SXperimental
ordhard, Fennville on apple was assumed to be a susceptible
strain since it was reported that this ordhard had not been
sprayed for two years. However from the mortality curve and
the slope of the line it does not seem to be a normal
susceptible strain indicating that resistance is not
completely lost even after the use of phosphate acaricides
was discontinued for two years. Two strains H and E collected

from cherry and a third strain D collected from crab apple

-25-

.3 samuum ucmumwmmu umwma mnu :uHB poumaéoo owumu xocmuom

.‘

 

 

mo.m mm.m Haoo.-eeoo. smoo. m Amsaamv 3mm 2mm 2
wH.mH mw.m owfio.-oHHo. meso. m Amfiaamv 3mm 2mm a
om.om mm.q oomo.-oNHo. ommo. m Amflaamv wowemm a
me.mH eN.q ommo.-omfio. oafio. m Amhaamv Homcmm e
mo.mH aa.m oafio.-wHHo. omao. m Aofiaamv esofiou H
He.N mHoo.-wooo. Hfioo. m Aawuoeovowamfio 5mm :
Hw.HN NH.q oflmo.-owfio. came. m Agnfiavuwamgo sum u
sm.m ma.m emoo.-oNoo. smoo. m Amfiaamv mHHu>ccmm a
om.m mH.N msoo.-omoo. “moo. m Aauwm30v mHHa>ccma m
Na.~ 0N.N omoo.-mmoo. omoo. m Amhaam nmwov mflfla>camm a
ms.a mq.m wmoo.-msoo. Nmoo. m mflaamv mHHH>ccmm o
wa.m mm.m oHHo.-oaoo. omoo. m Amaaamv mHHa>acmm m
“N.m mm.N «soc.-mmoo. smoo. m Aofiaamv mHHH>ccmm a
u...0..aum..a QGHH m0 ON\®H AGOHuMHquUCOO mCOquUHHQQH mmuHE m0 GUHSOm
hosmuom macaw muHEHA ucmoummv mo HonEsz
moameauaoo om-na

 

 

.HomH .cmwfisoflz cumumosnusom mo mmoum ucmummmwv Scum wouomafioo
muHE pop mammoasm mfiu mo mcflmuum :o m%mumm cownumuma mo muommwm mnu wcflsozm mmeSum anoumuonmq .N mHQMH

99-99 -26-

RTALITY

\_

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P F. R CE HT

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9 5‘
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{AH 002 004 008 c2 04

PERCENT CONCE NT RAT! O N

FIG.1: Dosage-mortality curves of Panonychus ulmi (Koch)

in response to parathion.

4L

 

.L—.

I
2
,4

 

C
Q

P 'r'K/th:

-27-
were equally susceptible to parathion when compared to the
strain A that was collected from the experimental orchard,
Fennville on apple. Strain H however showed slightly higher
susceptibility to parathion when compared to the other
three strains. The potency ratios of different strains of
Eurogean red mites when compared with the most susceptible
strain H, are presented in Table 2. Strains G and K collected
from Eau Claireand Bangor on plums and apple showed some
differences in the LD 50s when compared to the most
susceptible strain H. Data indicated a 22 fold resistance for
the strain G collected from Eau Claire on plums over the
strain H collected from Eau Claire on cherry and a 7 fold
resistance over the strain A collected from the experimental
orchard, Fennville on apple. Data for the strain K collected
from Bangor on apple showed a 21 fold resistance over the
strain H and a 6 fold resistance over tae strain A. Data
for all the other field collections showed intermediate
levels of resistance between those for strains A and G.
Strains J and I showed a 15 and 13 fold resistance over
strain H. respectively. All the strains differed significantly
in potency as determined by the method described by Litchfield-
and Wilcoxon (1949). This further indicates that the
European red mites in southwestern Michigan are becoming
resistant to parathion.

The diversity of the response or the heterogeneity
of the populations towards parathion looks very conSpicuous

judging from the lepes of the lines. The lepe function

-28-
values (S) ranged from 2.15 to 4.39. and were calculated by
the method described by Litchfield and Wilcoxon (1949). It
is interesting to note that the lepe of the line seems to be
correlated with the LD 50 values ie.the slope lowers with
the increase in LD 50. This may be true in case of heterogenous
populations like the ones tested here and up to a certain
degree of resistance.

There have been numerous reports of resistance to
organOphosphorous compounds by mites but quantitative data
have not been found. From the log dosage probit lines it is
apparent that there is a relation between the decrease in
susceptibility and increase in heterogeneity towards parathion.
The resistant strains were considerably more heterogenous
towards parathion than the less resistant ones. But in a few
instances data are available to show decrease in heterogeneity
after resistance has reached a high level. Lindgren and
Dickson (1945) and Yust gt 3.1. (1951) found that HON — resistant
California red scales which had a high LD-SO and a rather low
slope of the dosage-mortality curve, deve10ped super resistant
strains of higher LD-SOs and steeper slopes upon severe
selection in the laboratory. When curves were also compared
for parallelism with the curve of strain H from the slope
function ratio, only the curves of strains J,K and L were
found to deviate significantly (19/20 probability) from
parallelism.

The slope of the lines and the level of the resistance

(Between 2 to 22 fold) indicate that the mites are becoming

-29-
resistant but that the level of resistance has not reached
a high level. Taylor and Smith (1956) reported a 100 fold
resistance of resistant two-spotted mites strains over the
susceptible strains.

The method by which mite resistance can develop
indicates that resistance may appear in any area in which
phosphate acaricides or nonselective phosphate insecticides
with acaricidal activity are applied frequently. A record
of previous applications of chemicals was known for some
orchards in wnich mites were collected. The plum orchard at
Eau Claire from where the strain G was collected had
regularly been sprayed with parathion for 6 to 7 years for
mite control. This strain was the most resistant among the
strains tested. The apple orchard at Bangor from which the
strain K was collected (21 fold resistance) had also been
frequently sprayed with parathion. The experimental orchard
at Fennville from WAiCh strain A was collected had not been
sprayed with any pesticides for two years and the resistance
appears to have been reduced to some extent but not lost
altogether. Strains H and E, collected from cherries were
the most susceptible to parathion. Parathion had been used
sparingly in this orchard. Dieldrin and lead arsenate or
Diazinon had been employed for the control of plum curculio
and cherry fruit fly, reSpectively. The host might have
something to do with the lack of resistance. There are
no reports about any insect developing resistance on

cherry. The development ofresistance by EurOpean red mite

-30-
to parathion is the culmination of a selection in which the
most resistant individuals have been brought together to
form a genetically fixed resistant strain. The selective
agents have been parathion and various phosphorous
pesticides.
Out of the 13 strains of European red mites tested

with parathion, biOassay tests with malathion were made on
six strains-A,E,G,H,K,and M. The data on finese tests is
presented in Table 3 and the mortalitywmmrves as in Figure 2a
The LD 50s with their confidence limits, slope of the line,
and fine potency ratio were determined by the method described
by Litchfield and Wilcoxon (1949) and are given in Table 3.

From the Chi2

test it was found that all the lines were a
good fit and the data were not heterogenous. From the
mortality curves it is apparent that the European red mites
tested were also resistant to malathion. The level of
resistance to malathion, however is higher than that of
parathion. Data showed that strain G collected from Bau Claire
on plum had a 30 fold resistance over the least resistant
strain H collected from Eau Claire on cherry. Strain K
collected from Bangor on apple showed a 13 fold resistance
over the strain H. This further demonstrated that the host
from which the mites were collected might have something to
do with resistance. The mite strain from plum was found

to be the most resistant both to parathion and malathion.

Similarly mite strains from cherries were most susceptible

both to parathion and malathion. Organophosphate chemicals

.: Cashew ucmumfimou unwoa ecu mo OmuQA msu :uHB pmquEoo out mcflmuum oLu mo m.omuQA uoflumu socmuom

\
‘ul

 

-31-

 

ma.m ma.N one.-smo. mac. n Aoaaaev sea sea 2
Ha.ma om.N oaa.-ama. mma. m Aoaaaev senses a
wN.N who.-aoo. «Ho. m Asnnoaovoaaeau sea :
oo.om Hw.H ooe.-mam. ohm. m Asaaavanaeao sea a
no.m am.a mmo.-amo. mac. n snnoeov oaaa>eeoa a
ma.a oa.a mmo.-aao. HNo. m Aoaaaev oaaasaeoa e
wowumu mafia mo ON\mH Acowumhucmocoo mcofiuMUHHamH mmuHE mo oopsom
mucouom oaon muHEHq unmoummv mo unpasz
ooeeoaaeou om-aa

 

 

.HomH “sewage“: cumumoszusom mo mmmum ucmHmMMHp Eouw pouomHHoo
ouHE emu commonsm o:u mo mcwmuum so manage cowzumame mo muommmm mnu wswsosm mmprum kHOumuonmA .m manna

-32-

p
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Of)

---_..._.i._ - . ___...._...—. a- _J

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(32 “ '.(34 ’”'”TOE{” “ J""".2 "‘ "'T4
PERCENT CONC ENTRATION

FIG.2: Dosage-mortality curves of Panonychus ulmi

in response to malathion.

IT'Y

'
U
5.

iCRTA

IT by

tzEtfitgfl

(Koch)

-33-
are not as extensively used on cherries as on apple, and
this may be one of the reasons why mites and insects on
cherries have not develOped resistance to phosphates. The
development of resistance by European red mites to parathion
and malathion on apple is due to the selective agents such
as various phOSphorous pesticides. The resistant individuals
have been brought together to form a genetically fixed
resistant strain.

The resistance of European red mites to malathion might
be due to cross-resistance. Malathion is chemically similiar
to parathion so that resistance to parathion confers resistance
to malathion and possibly to other organOphosphorous compounds.

From the lepes of the lines it can be said that the
European red mite pOpulations of these six strains are less
heterogenous to malathion than to parathion. There also does
not seem to be any corelation between the decrease in
susceptibility and increase in heterogeneity to malathion.
Experiment III

The data on the bioaSsay tests on 3 strains of clover
mites with parathion and malathion are presented in Table 4,
and the mortality curves are plotted on log~dosage and
probit-mortality as shown in Figure 3. The LD-SOs with their
confidence limits, slope of the line and the potency ratio
were determined by the method previously described. From
the Chiztest it was found that all the lines were a good

fit and the data were not heterogenous. From the LD-SOs,

it is apparent that the clover mites are highly

-34-

 

 

 

mm.H mmooo.umoooo. woooo. mm.H cocoo.unmooo. Noooo. m Axuuonovuuwmfio 3mm o
ae.a goo.-mmooo. eaooo. am.- oHoo.-anooo. eaooo. m Aoaaaev noweem a
sq.H Hmooo.nmmooo. Nwooo. N¢.H Nwooo.uwoooo. whooo. m Aofiaamv oHHH>scom <
mafia oN\mH A.osoo mafia ON\mH A.o:oo .waou mmqu mo condom
mo uflEHH ucoouomv mo quHH unmouomv mo
oaofim mocopwmcoo owned oaon moampwmcoo owned HonEDZ

cowsuwfimz cownumumm

 

 

mo mcflmnum so mammam COHSUmHmE was cofizumuma mo muommmo mfiu

.mmuwe um>oHo
so moHvSum muoumuoan .q oHLMH

° P
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-35-

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PERCENT (N3 CENTRATIOi

Ap:Strain A tested with parathion.Bp:Strain B tested with parathion.

Asztrain A tested with malathion.Bm:Strain B tested with malathion,

FIG. 3. Dosage-mortality curves of Bryobia praetiosa Koch in
response to parathion and malathion.

-35-
susceptible both to parathion and malathion. The LD-SOs
for the 3 strains range from .00062 to .00094 percent
concentrations to parathion and malathion. From the potency
ratios it was found that there was a significant difference
in potency to parathion between the strain B which was
collected from Bangor when compared with the most susceptible
strain C which was collected from Eau Claire on cherry.
However there was no significant difference in potency of
this strain to malathion when compared with strain C.
Strain B did not differ significantly in potency to both
parathion and malathion.

Judging from the lepes of the lines the homogeneity
of the clover mite pOpulations to the organophOSphorous
compounds looks very apparent. There also seems to be a
strong indication that the clover mites in orchards
might not become resistant to organOphosphorous compounds
in near future in Michigan. The only explanation for the
non-resistance of the clover mite to organOphOSphorous
compounds might be due to the fact that the clover mite is
not a regular pest on commercial orChards in Michigan and
hence are not exposed to the organophosphorous treatments
as much as the EurOpean red mites and two-spotted spider

mites.

Part B

Experiment I.

The results of the bioassay tests on 5 field strains
and one greenhouse strain (red clover) of two-spotted
spider mites with parathion and Kelthane are presented in
Table 5 and the dosage-mortality curves are plotted on
log-dosage and probit-mortality as shown in Figures 4 and 5.
The LD 503 with their confidence limits, slope of the line and
the potency ratio were determined by the method previously
described. The LD 508 were expressed in terms of pounds of
toxicant per 100 gallons of water. From the Chiztests it
was found that all the lines were a good fit and the data
were not heterogenous. From the LD-SOs it is apparent that
the two-spotted spider mites are becoming resistant to
parathion. The LD-50s range from 0.50 to 4.70 lbs. of
parathion per lOO gallons of water. The resistance has not
reached a high level. From the potency ratio it was found
that there was a significant difference in potency to
parathion between the strains A,B,D and B when compared
with the most susceptible strain 0 which was collected from
Bangor on crab apple. The greenhouse strain F which was
collected from red clover and reared on beans for two years
in the greenhouse did not show any significant difference in
potency when compared with the strain C and was equally
susceptible to parathion as the strain C. This indicates
that the greenhouse strain which was collected from red clover

-37-

-€38-

 

 

ee.m ma.o-ao.o NH.o am.m no.0-oe.o mm.o e Ano>oao eoav
samuum endoscoouo m

Ne.N am.o-sa.o HN.o an.a om.m-o-.e oh.e e Aoaaanv shaman m

am.N HN.o-m-.o NH.o Na.m oN.H-Ha.o ma.o e Ao-aaov oaaa>eooae a

mo.m na.o-oH.o ea.o ae.N ee.o-am.o om.o e Aoaaaev aoween o

nH.N ea.o-ao.o NH.o oo.N aw.m-ow.~ om.m e Aoaaaev oaasseeoa a

Nw.m am.o-HN.o am.o me.m eH.N-om.H om.a e Aoaaaov sonata a

mafia oN\mH A.Hmm . mafia 0N\mH A.Hmw .wamu mouHE mo oousom

so oases ooH\nHv so sheds ooH\nHv so

maon mosmuflmcoo owing macaw mocmwwmsoo OmuQA nmnfisz

outfiuamm COHsumhmm

 

 

.HomH .smwwnoflz snoumoBSuSOm mo mmopm ucoummmwv Eouw pmuomHHoo mouwe Hopwam
pouuoamnosu mo mcflmuum so manuam osmsufimz was COflSumpma mo muoomwm ens so mmwwSHm au0umuonmq .m oHan

-39-

i
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Fannie-IN iCW <3ALS.

FIG.4: Dosageemortality curves of Tetranychus telarius (L.)

in response to parathion.

PERCENT MOhTLLITY

f‘.
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(a, ”7.5 a O I 2 7

POUNDS iN IOO GALS'

FIG.5: Dosage-mortality curves of Tetranychus'telarius

(L.) in response to Kelthane.

-41-
and maintained in the greenhouse for two years on beans

did not lose it's susceptibility to organOphOSphorous

compo nds. The level of resistance indicates that the mites
have not deveIOped a high level of resistance but are
becoming resistant to parathion. Taylor and Smith (1956)
reported a 100 fold resistance of resistant two-Spotted
spider mite strains over the susceptible strains. Data

for the field collections from different areas and the
greenhouse strain do not show any marked differences in
susceptibility of the two-spotted spider mites to Kelthane
that would indicate any substantial amount of Kelthane
resistance in these strains. The LD-50s range between

0.12 to 0.29 pounds per 100 gallons. The potency ratios

do not show any significant difference in potency to
Kelthane. The lepes of fiielines indicate diversity of the
response or the heterogeneity of the populations towards
parathion and Kelthane. The susceptibility of the Bangor
strain C to parathion might be because the crab apple trees
from which fliis strain was collected had sparingly been
sprayed with pesticides as the trees were neglected. The
relatively resistanct strains A,B,D and E were collected from
commercial orchards where the organophOSphorous compounds
though not much used for mite control are frequently been
used for the control of other orchard pests. Acaricides other
than organophosphorous compounds are commonly and effectively
used for two-spotted spider mite control and hence the

resistance has not develOped to a high level to parathion.

SUhRARY

Mite counts from 8 varieties of apple from the
experimental orchard located at Fennville, Michigan were
made by using a brushing machine ( Henderson and McBurnie
1943, Morgan gplgL 1955) and a binocular micrOSCOpe, to
study the response of apple varieties to the mite infestation.
Bioassay tests were carried out on European red mites,
Panonychus ulmi (Koch), clover mites, Bryobia praetigsa,
Koch and two-spotted Spider mites, Tetranychus telarius
(L.) to determine the susceptibility of the orchard mites
from different orchards in southwestern Michigan, to the
organophosphorous compounds, parathion and malathion.
A modification of the leaf disc method as described by
Rodriguez (1958), and Hoyt and Harries (1961) was used to
test the Burcpean red and clover mites. A modification of the
method as described by Cleveland (1960) and Andres and
Reynolds (1958) was used to rear and test the two-spotted
spider mites. Bioassay tests were made to determine the
effectiveness of Kelthane on two-spotted spider mites
resistant to parathion. The results of these experiments are
outlined as follows:

1) Mite populations were found to be highest in Red
.Delicious variety. Yellow Transparent, Grimes Golden
and Jonathan varieties were more susceptible to
mites than Wagener, McIntosh, Healthy and Dutchess.

Clover mite populations were maximum on Yellow Transparent.

-42-

2)

3)

4)

5)

6)

7)

-43-
Resistance to parathion and malathion was evident
with the EurOpean red mites.
The level of resistance to malathion was slightly
higher than dust to parathion. Strain collected from
Eau Claireon plum and a strain collected from Bangor
on apple showed a 22 fold and a 21 fold increase in
LD-SOs to parathion and a 30 fold and a 13 fold increase
in LD-SO to malathion over a susceptible strain.
Mites collected from cherries were most susceptible
to parathion and malathion.
European red mite populations showed more diversity
of the response or heterogeneity towards parathion
than towards malafiiion.
Clover mites were highly susceptible to both parathion
and malathion. The mite pOpulations did not show any
heterogeneity towards parathion or malathion.
Two-spotted spider mites also showed evidence of
resistance to parathion. The level of resistance had
not reached a high level. One strain showed a 9 fold
increase in the LD-SO over a susceptible strain.
A susceptible strain of two-spotted spider mite
collected from Red clover and maintained in the
greenhouse on beans did not lose its susceptibility
to parathion even after two years.
Farathion-resistant two-spotted spider mites were
easily controlled with Kelthane. The data did not

indicate any resistance to Kelthane.

-44-

8) Resistance of Burcpean red and two-spotted spider
mites to parathion and malafliion has developed due
apparently to the frequent applications of various

phOSphorous pesticides.

 

CHLMICAL means or rRorh :TARY ochrouwhs RthRRED To 13 THIS

Aramite

chlorobenside
Chlorobenzilate

demeton

Diazinon

ethion

Genite

Guthion

Kelthane ‘

malathion

ovex

parathion

Tedion
EFT

Trithion

2-(p-tert-butylphenoxy) is0propyl 2-chloroethyl
sulfite.

p-chlorobcnzyl p-chlorophenyl sulfide.

ethyl 4,4'- dichlorobenzilate.

: 0,0-diethyl 0(and S)-2—(ethylthio)

ethyl phOSphorothioates.
0,0-diethyl-O-(2-isoproy1-4-methyl-6-pyrimidyl)
thiophosphate.

0,0,0'-tetraethyl-S,S'-methylene
biphosphorodithioate.

2,4-dichlorophenyl benzenesulfonate.

: 0,0-dimethyl S-(4-oxo-l,2,3-benzotriazin

-3(4H)—yinethy1) phosphorodithioate.

: l,l-bis(p-Chlorophenyl)-2,2,2—trichloroethanol.

S-(l,2-dicarbethoxyethyl)0,0-dimethyl

dithiophosphate.

: p-chlorophenyl p-chlorobenzenesulfonate.

O.

0,0-diethy1 O-p-nitrophenyl phosphorothioate.
2,4,4', 5-tetrachlorodiphenyl sulfone.
tetraethyl pyrophOSphate.

0,0-diethyl S-p-chlorOphenylthiomethyl

phosphorodithioate.

-45-

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-52-

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-55-

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"INtfltfifitfl'flttT1155