Extent and significance of azinphos- methyl resistance in

Extent and significance of azinphosmethyl resistance in codling moth
AP142
Graham Thwaite
NSW Agriculture
AP142
This report is published by the Horticultural Research and
Development Corporation to pass on information
concerning horticultural research and development
undertaken for the Apple & Pear Industry.
The research contained in mis report was funded by the
Horticultural Research and Development Corporation with
the financial support of Eastern Metropolitan
Fruitgrowers, Harcourt and District Fruitgrowers, NSW
Farmers Assoc - Orange Fruit Branch, Orchardists and
Fruit Cool Stores Assoc of Victoria, Bayer Australia,
Colin Campbell Chemicals, Incitec Pty Ltd, Koor
Intertrade Pty Ltd, Rohm and Haas Aust Pty Ltd and
Wellcome Australia Limited.
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expressing the opinion of the Horticultural Research and
Development Corporation or any authority of the
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The Corporation and the Australian Government accept
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© Copyright 1996
CONTENTS
Industry Summary
3
Technical Summary
4
Recommendations
5
Technical Report
6
Introduction
6
Results
9
Discussion
23
Conclusion
26
Acknowledgments
26
References
27
Appendix 1
List of cooperators
28
Appendix 2
List of contributors
30
Appendix 3
List of publications
31
3
Extent and Significance of Azinphos-methyl Resistance in Codling Moth
W G Thwaite, AR&VC Orange and D G Williams, IHD Knoxfield
INDUSTRY SUMMARY
Codling moth is a very destructive pest of apples and pears throughout the world.
Without adequate control it will cause damage to fruit and renders it unsaleable. Since
1960, pome fruit growers in eastern and central Australia have used a program of
azinphos-methyl sprays to control the pest. Azinphos-methyl has, in almost all situations,
provided excellent control of codling moth such that the pest has been virtually absent
from many orchards for 30 years.
Control began to decline in some orchards in the 1970s and 1980s. In almost all cases,
the problem was corrected by attention to spray application techniques. In 1991, the first
evidence of resistance was detected in Victoria and shortly afterwards in codling moth
from Queensland. A research program in 1991/92 and 1992/93 set out to determine how
widespread the resistance had become and how serious it was on individual orchards. The
work was joindy funded by the agricultural chemical industry, local fruit grower
organisations and HRDC.
Extensive sampling and testing of codling moth in south-east Queensland, New South
Wales and Victoria revealed levels of resistance up to 7 fold, although most populations
did not exceed around 4 fold. In the two orchards most seriously affected (at Forbes and
Orange in New South Wales) control of codling moth using azinphos-mediyl was
unsatisfactory and serious economic injury was caused despite otherwise adequate spray
schedules.
Sex pheromone traps as a device to capture moths for treatment with azinphos-methyl
to detect resistance were used in each of the two seasons. This potentially simple and
inexpensive method was not effective in Australia, unlike its success in western USA.
Because a rapid resistance diagnostic technique was unavailable, the survey for resistance
was restricted.
Apple and pear crops in eastern mainland Australia are now at risk from increasing
codling moth damage brought on by resistance to the key chemical used for its control.
There is every likelihood that crops in South Australia will also be at risk. Research is
now urgently needed to provide growers with a resistance management strategy to
overcome the resistance problems. In the meantime, orchardists should carefully check
their spray machinery and pesticide application practices to ensure that the products in
current use are applied effectively.
4
Extent and Significance of Azinphos-methyl Resistance in Codling Moth
W G Thwaite, AR&VC Orange and D G Williams, IHD Knoxfield
TECHNICAL SUMMARY
Azinphos-methyl has been used for more than 30 years to control codling moth, the
most destructive pest of apples and pears in south-east mainland Australia. In 1991, the
first case of suspected resistance was detected in southern Victoria and shortly afterwards
confirmed from an orchard in Queensland, with a resistance factor (RF) at the LCJQ of 2.6.
In 1991/92, an extensive survey of orchards in south-east Queensland, the BathurstOrange, Forbes and Batlow districts of New South Wales and the Goulburn Valley in
Victoria was undertaken using a sex pheromone trap technique developed as an effective
resistance diagnostic method in the USA. Dose-mortality data for adults were compared
between a standard bioassay technique (LCJO 0.11 gac/L) and with moths stuck to trap
bases (LCJQ 0.17 gac/L). Discriminating doses (DD) were established as 0.5 and 1.0 gac/L
respectively.
A total of 460 traps were deployed in 1991/92 in 23 orchards but these yielded only
436 moths. Traps were in the orchard for one night only. Dose-mortality data from two
of these orchards failed to provide any clear indication of resistance, nor was it detected in
the limited testing possible in 12 other orchards. The technique was further tested in
1992/93 in three orchards in which resistance was proven using the standard technique.
1321 moths were caught in 537 traps. Only one orchard (Centofanti, Orange) had an
elevated LC^, RF 1.8. However, all three strains had much higher LQ^s than the
susceptible strain.
Larvae were captured in corrugated cardboard for rearing to adults in bom 1991/92 and
1992/93. The larvae were either from fruit (3 orchards) or tree trunks (23). Testing at the
DD was possible for 23 groups of moths from field collected material and all except 2 (1
each in 1991/92 and 1992/93) exhibited tolerance or resistance to azinphos-methyl. The
most resistant strains in 1991/92 were from Girot (6.4) and Centofanti (6.3) fold RF «t the
LCjo. Resistance in the Girot strain appeared to increase between 1991/92 (39%) and
1992/93 (22%) mortality or moths treated with 0.5 gac/L.
Dose mortality data were also obtained for the effect of azinphos-methyl on newly
hatched larvae. An LCso of 0.008 and LG*, of 0.12 gac/L as a deposit on fruit were
established. Limited testing of field strains failed to detect resistance in larvae.
Resistance to azinphos-methyl was diagnosed in codling moth collected from 19
orchards in south-east Australia.
5
Extent and Significance of Azinphos-methyl Resistance in Codling Moth
W G Thwaite, AR&VC Orange and D G Williams, IHD Knoxfield
RECOMMENDATIONS
Extension/adoption by industry
Growers need to be made aware of the many instances of failure of azinphos-methyl to
provide the excellent control of codling moth the industry had come to expect At this
point the overall magnitude of resistance is low, but there is potential for the problem to
become very serious, very quickly. It is also important for orchardists to carefully check
spray application techniques and spray equipment
Directions for future research
One of the targets within this two year project was to evaluate sex pheromone traps as a
resistance diagnostic tool. The traps did not provide the same type of information as they
appear to have done in the USA where the technique was developed. There is an
important need for a rapid diagnostic test for resistance to replace the slow process of
rearing moths from larvae.
The second urgent need is for growers to be provided with information to enable them
to successfully manage a resistant population. A management strategy is also required for
orchards without a resistance problem to try to prevent resistance developing. Research is
needed to find appropriate pesticides to use as an alternative to or in rotation with
azinphos-methyl. This would involve laboratory bioassays to establish patterns of crossresistance and field trails to prove robustness of the strategy. Other options include the
use of codling moth mating disruption using sex pheromone dispensers and the
development of biological control, such as the use of insect parasitic nematodes.
Provision of a robust resistance management strategy for codling moth is imperative if
growers are to maintain control of this serious pest
6
TECHNICAL REPORT
Introduction
Azinphos-methyl is the insecticide used by most apple and pear growers in Queensland,
New South Wales, Victoria and South Australia to control codling moth, Cydia pomonella
(L.), the industry's most destructive pest. The insecticide was first recommended for
codling moth control in 1959 following the discovery of resistance to DDT in the late
1950's (Morris and Van Baer 1959; Lloyd 1960).
There has been some grower discontent with azinphos-methyl for many years, but
generally most cases of inadequate control could be attributed to deficiencies in spray
application methods and timing. However there was a small number of growers who
claimed tiiey constantly have control problems, usually in specific blocks, for which there
appeared to be no adequate explanation.
Suspected resistance
The possibility of resistance to azinphos-methyl in codling moth in Australia has been
raised from time to time but it was never detected in laboratory testing (Thwaite unpublished). A review by Croft (1982) reported that no case of resistance to azinphosmethyl had been recorded in the world to that time despite more than 20 years of its use
in some apple and pear orchards. A number of suspected control failures have been
reported, e.g. Reidl et al. 1986, but it was Varela and Welter (1990) who first confirmed
resistance in a California pear orchard.
Four cases of suspected resistance, two in Victoria and one each in Queensland and
New South Wales, were investigated in 1991. Once resistance was confirmed in one of
these, other orchards in the three states were surveyed to determine the extent of
resistance. This report documents our findings over two growing seasons, 1991/92 and
1992/93.
Materials and methods
Collection of adults
Three methods were used to obtain codling moth adults for testing:
1. Reared from overwintering larvae captured on tree trunks
2. Reared from larvae within fruit
3. Captured in sex pheromone traps.
Overwintering larvae. Some first generation and most second generation codling moth
larvae spin cocoons on the trunk of host trees and hibernate during the winter (Geier
1981). Cocoons are usually found under the bark although larvae will take advantage of
holes or depressions in the trunk, crotch or main limbs to hibernate. If artificial shelter is
provided, this will often become a favoured hibernation site, especially if the tree trunk is
smooth.
In some orchards, larvae were removed directly from the tree trunk and placed into
containers with corrugated cardboard and allowed to respin cocoons. In others, corrugated
cardboard bands were placed around tree trunks in February to capture larvae. Bands
were removed during winter. The larvae in cardboard were held in a coolroom at 3-4°C
for about four weeks before transferring to a controlled environment room (26°C, 50%
RH) until adults emerged.
7
Larvae from fruit. When a grower advised that fruit was damaged by codling moth,
fruit likely to be infested with larvae were picked and placed into seedling trays with two
layers of corrugated cardboard around the perimeter. As larvae emerged they spun
cocoons between the layers of cardboard. Progeny of the first (spring) brood of moths did
not require chilling prior to pupation and emergence, but late season larvae were chilled to
break diapause.
Pheromone traps. In nature, male codling moths are attracted to virgin females via a
chemical signal or pheromone released by the female. The pheromone has been copied
and used in rubber dispensers or caps for use in sticky traps devised for pest monitoring.
A technique for using sex pheromone traps for capturing "ferel" male codling moths in
the field for resistance testing was described by Riedl et at. (1985) and modified by
Varela and Welter (Thwaite 1990).
In 1991/92 in New South Wales and Queensland, cardboard pheromone traps, a locally
made version of the Pherocon 1C design, were used. The trap bases measure 226 x 278
mm and each was marked with a 20 x 20 grid taking in an area 120 x 240 mm in the
middle. Coordinates were identified by the letters A-F across the top and 1-12 down the
side which enabled the treatment details of individual moths to be recorded. Shortly
before taking the bases into the field, a think film of Tangletrap® (The Tanglefoot
Company, USA) was applied to the grid area, approximately 4 g/base. A pheromone
dispenser was suspended from the top of the trap using a pin. Dispensers were stored in a
freezer before and between uses.
In Victoria, commercially available pheromone traps (Agrisense-BCS delta design) were
used. Excess adhesive was removed from the bases and the cap placed in the middle of
the base. The bases were not marked with a grid.
For the 1992/93 season, commercially available Trece Pherocon 1C traps (Pest
Management Supply Inc, USA) were obtained for use in both New South Wales and
Victoria. No trapping was attempted in Queensland in 1992/93.
Codling moth adults are active around dusk when the air temperature exceeds 15°C.
Only males are attracted to sex pheromone traps. Traps were placed at about 2 m high on
a convenient limb on the perimeter of a tree in the afternoon and removed either later the
same night or early the following morning. Trapping was only attempted when weather
conditions were favourable for moth flight Traps were returned to the laboratory and
stored in cool conditions until the moths were treated.
Adult bioassays
All adult bioassays were by topical application using an Arnold hand microapplicator
(Burkard, UK). A 1 uL droplet of azinphos-methyl technical grade (Bayer Australia
Limited 1991/92 and Makhteshim Chemical Works, Israel 1992/93) in acetone or ethyl
methyl ketone (EMK) was deposited on the dorsal thorax of the moth. The two technical
materials were compared in bioassays and were found to produce equivalent results.
Experimental controls were treated with solvent only. The age did not exceed 3 days in
tests on moths from all sources except pheromone traps where the age was unknown.
Prior to treatment, moths which were not otherwise immobilised (on sticky traps) were
anaesthetised using carbon dioxide. Following treatment they were held in controlled
environment conditions (26°C, 55%RH, constant light) for 24 hours before mortality was
assessed, unless otherwise specified. Moths with unrestricted movement (i.e. not on sticky
bases) were held in perspex cylinders, 80 mm internal diameter and 50 mm high, with a
8
90 mm diameter glass petri dish at the base and a plastic petri dish lid with three air holes
on the top. Moths on sticky bases were left exposed on the shelf of the controlled
environment room.
Unrestricted moths were declared dead if, when gently prodded with a needle, they
were incapable of flight Moths on the sticky base were prodded gently and if there was
no movement (antennae, legs, body) the moth was declared dead except that where there
was slight movement of the claspers only, the moth was regarded as dead. Mortality data
were, where possible, corrected for control mortality using Abbott's formula (Abbott
1925).
Tests were either discriminating dose (DD), that is the concentration of insecticide
which should kill all or almost all of the individuals treated if they are susceptible, or to
determine a dose response line (DRL) to calculate resistance factors. It was often
necessary to test moths in small groups to obtain sufficient numbers within the restricted
age range (0-3 days). The data from individual tests from the same strain were then
pooled. Analysis of dose response was carried out using a probit program on a personal
computer which generated dose-mortality statistics such as the LCJQ (the concentration
lethal to 50% of individuals tested) and the LC,, (lethal to 99% of individuals tested) and
the slope of the DRL. The LC^ approximates the discriminating dose.
Comparison of pheromone trap versus unrestricted moths. Specific tests were carried
out to compare the DRLs obtained when moths were stuck onto trap bases or had
unrestricted movement. The laboratory strain was used and about 25 male moths were
gently stuck to each of five bases. Slight warming of the bases softened the Tangletrap
and improved adhesion. Moths were topically treated, the results assessed then analysed
as previously described.
Larval challenge
Azinphos-methyl applied to fruit protects it from attack from newly hatched larvae.
The insecticide is also active against eggs about to hatch as well as adults (Thwaite 1984).
It is possible that resistance could occur in larvae and not adults or vice versa.
A bioassay technique for larvae which involves dipping fruitlets in insecticide and later
challenging each fruitlet with a neonate larva has been described (Thwaite 1985). The
technique was used to screen for resistance to azinphos-methyl in larvae of codling moth.
Dose mortality data. Granny Smith fruitlets harvested in the previous December were
dipped in batches of 50 in aqueous suspensions of azinphos-methyl (Gusathion® 350 g/kg
wp), allowed to drain and air dry. Five replicates of 10 fruits at each concentration were
challenged by placing a newly hatched codling moth larva from the culture onto the fruit
using a fine brush. Fruit dipped in water only were used as controls.
The containers of 10 fruit (a replicate) were left open and held in a controlled
environment room at 26°C, 55% RH under low intensity light for one week after which
assessments were made. Each fruit was dissected and the fate of the larva determined.
Four experiments were conducted, two over a concentration range of 1.95 to 31.25 x
10'3 (grams active constituent per litre) and two from 1.0 to 30 x 10'3 gac/L. Mortality
data from the two experiments in each set were pooled and analysed using the probit
program to obtain dose-mortality statistics.
9
Resistance survey. As larvae became available from codling moths reared from various
orchards, they were used for fruit challenge to survey for resistance. Fruit were dipped in
a suspension of azinphos-methyl 0.01 gac/L with water dipped fruit used for controls. A
similar number of treated fruits were challenged with larvae from the laboratory
(susceptible) strain.
Results
Victoria 1991192
Codling moth was obtained from two orchards at Bacchus Marsh1 in southern Victoria
where poor control of the pest had been observed in the 1990/91 season. Upon
emergence, moths were treated by topical application using a DD of 0.4 gac/L azinphosmethyl in acetone (D S Morris, unpublished).
Corrected mortality data are given in Table 1. Assuming the DD established 30 years
ago is still valid, these data provide evidence of resistance to azinphos-methyl at Bacchus
Marsh. However testing was confined to the field strains - there was no susceptible field
or laboratory strain with which to make a comparison.
Table 1. Mortality* of codling moth adults from two Bacchus Marsh apple orchards, 1991
Delios strain
Durham strain
No. tested
No. dead
No. tested
No. dead
Az-methyl 0.4 gac/L
20
4
21
5
Control (acetone)
6
1
10
0
Corr. mort. (%)
4.0
23.8
A
After 48 hours at 25°C
These strains warranted further investigation to confirm resistance. However the
growers improved their spraying technique and in 1991/92, codling moth infestation was
negligible (Figure 6). No moths from 1991/92 were available for testing.
Pheromone trap technique. A limited amount of trapping was undertaken in the
Goulburn Valley, Victoria (Table 8). No meaningful data on resistance status of moths
were obtained.
Victoria 1992/93
Further testing of the Durham (Bacchus Marsh) strain moths reared from larvae from
infested fruit and a DD of 0.4 gac/L showed that resistance, first detected in 1991, was
still present in the population (Table 2).
1
A list of all growers and the location of orchards is given in Appendix 1
10
Table 2. Response of Durham strain adult codling moth to azinphos-methyl 0.5 gac/L
compared with Orange laboratory strain, 1993
Strain
Orange
Durham
Treatment
Az-methyl
Control
Az-methyl
Females
Tested
Dead
26
10
4
0
8
6
Males
Tested
Dead
23
14
6
1
10
9
Total
Tested
Dead
49
24
10
1
18
15
49.0
10.0
83.3
Mortality (%)
The corrected mortality for Durham females and males was 38.5% and 53.1%
respectively, 43.3% for both sexes combined. Mortality for the Orange strain was 75%
and 90% for females and males respectively. The numbers tested are too small to draw
conclusions about the differences in response between the sexes and between the 83.3%
mortality in the Orange laboratory strain in Victoria compared with the usual 90+% result
obtained in NSW.
Queensland 1991/92
Adults from overwintered larvae. Approximately 250 larvae in trunk bands were
forwarded to Orange from die Zorzi orchard, Cotton Vale (near Stanthorpe) Queensland in
winter 1991. The orchard had a recent history of heavy codling moth infestation. Initial
testing comparing the response with the Orange laboratory strain (Table 3) provided
evidence that there was resistance in the Zorzi strain.
Table 3. Mortality of two strains of codling moth adults treated with azinphos-methyl
n
Strain
Laboratory
100
(susceptible)
Zorzi, Qld
Resistance Factor
100
gac/L
(95% CI)
LG*, gac/L
(95% CI)
Slope
(±SE)
0.19
0.46
5.89
(0.15-0.23)
(0.33-0.64)
(0.54)
0.48
5.12
2.26
(0.27-0.84)
(0.95-27.7)
(1.10)
2.6
11.1
LCJO
These results are based on only 20 moths at each concentration, but the difference in
response between the strains is clear. Figure 1 graphs the data and the Zorzi line suggests
that the strain is heterogenous (contains a mixture of susceptible and resistant individuals).
11
Adults were reared from larvae in bands from three Stanthorpe district orchards and the
mortality at the DD for each strain compared with the Orange laboratory strain is given in
Table 4. Dose-mortality statistics are shown in Table 11.
Table 4. Mortality of codling moth adults from Stanthorpe, Queensland treated with
azinphos-methyl
Strain
Orange lab.
Corr. mort
No. treated
0 (control)
110
11
0.5
134
127
0
62
1
0.5
42
27
0
30
0
0.5
13
8
61.5
0.5
11
6
54.5A
Zorzi
Harvey
GBHRI
A
No. dead
Az-methyl
(gac/L)
(%)
94.2
63.7
Uncorrected mortality
Pheromone traps. Limited trapping at Stanthorpe in January 1992 (Table 8) was
ineffective in detecting resistance even in the Zorzi orchard where resistance is known
(Table 3).
Table 5. Mortality of Stanthorpe district strains of codling moth, 1993
Treatment (azinphos-methyl gac/L)
Strain
0 (control)
0.5
1.0
8
5
56.7
Costanzo
(ex fruit, 2/93)
Treated
Dead
Corr. mort (%)
15
2
14
5
25.9
Laurie
(ex bands)
Treated
Dead
Corr. mort. (%)
10
0
39
20
51.3
Volpato
(ex bands)
Treated
Dead
Corr. mort. (%)
17
0
27
10
37.0
6
4
66.7
12
99.
95
S>
90
"5
*-»
o
A
/
Zorzi
Stanthorpe
x> 5 0
(D
*•»
O
©
v-
Orange
Laboratory
k.
O
O
10
5
1 J
Az-methyl
gac/L
p p p p p ^ .-*
'-* io co oi N o en
oo o> ->i to en o>
Co
en en
Figure 1 - Dose-response lines for the Orange laboratory (n = 100) and Zorzi Queensland
(n = 100) strains of codling moth using the standard bioassay technique.
13
Queensland 1992/93
Adults reared from larvae. Three strains from the Stanthorpe district were tested and
the results are summarised in Table 5 and Figure 4. All three strains are resistant to
azinphos-methyl based on the DD tests.
Pheromone traps. No attempt was made to carry out pheromone trap tests in the
Stanthorpe district in 1992/93 because results obtained in New South Wales failed to
establish the effectiveness of this method (Table 13).
New South Wales 1991192
Early testing concentrated on orchards in which growers had previously indicated a
problem. The first DD tests were on adults ex H & L Rayner orchard, Bathurst where
control of codling moth has been less than satisfactory for some seasons. The results are
given in Table 6.
Table 6. DD tests (0.5 gac/L) of adults reared from larvae ex tree trunks, Rayner,
Bathurst, September 1991
Date Range
A
Mortality
Number of Moths
Treated
Dead
(%)
24.9 to 12.10.91
20
15
75.0
18.10.91
6
4
66.7
Total
26
19
73.1
Uncorrected - no moths were treated with EMK alone
As the Rayner moth mortality is less than the > 99% mortality expected from the
laboratory (susceptible) strain (Table 3) it was provisionally concluded that tolerance of
resistance to azinphos-methyl occurs in the Rayner strain, but further testing was required
to confirm and quantify it
Table 7. Effect of azinphos-methyl on codling moth adults in a standard bioassay and on
pheromone trap bases
Method
Standard
n
383
(unrestricted moths)
Moths adhered
to trap base
257
LCso
(95% CI)
(95% CI)
Slope
(±SE)
0.11 gac/L
0.42 gac/L
4.05
(0.10-0.12)
(0.32-0.54)
(± 0.45)
0.17 gac/L
0.86 gac/L
3.34
(0.15-0.20)
(0.57-1.31)
(± 0.33)
LC99
14
Pheromone trap tests. Statistics generated from dose-mortality tests on the OPsusceptible Orange laboratory strain for both the standard bioassay and moths adhered to
trap bases are given in Table 7.
The L Q , for the adhered moths of 0.86 gac/L is very close to the 0.90 gac/L
communicated by S C Welter (unpublished) and is double that for unrestricted moths. For
resistance diagnosis using pheromone traps, 1.0 gac/L was established as the DD, and 0.5
gac/L confirmed as the DD for unrestricted adults.
Trapping was undertaken in 15 orchards in New South Wales between early November
1991 and March 1992 (Table 8).
Table 8. Codling moth resistance survey 1991/92 in New South Wales (N)> Queensland
(Q) and Victoria (V) - distribution of moth catches in sex pheromone traps
District
(State)
Orchard
Number of
Nights
Total
Traps
Total
Moths
Moths per
Trap
Orange (N)
Centofanti
8
80
113
1.4
Shea
3
20
34
1.7
W Culverson
3
35
1
<0.1
Leone
2
10
14
1.4
Other (3)
3
18
15
0.8
Rayner
8
102
170
1.7
BARS
2
8
8
1.0
Girot
2
14
31
2.2
Other (2)
2
20
1
<0.1
Batlow (N)
Combined (3)
1
30
15
0.5
Stanthorpe (Q)
Zorzi
2
45
8
0.2
Calvesi
2
25
13
0.5
Other (3)
1
35
10
0.3
Shepparton (V)
Combined (3)
1
18
3
0.2
TOTALS
23
460
436
0.95
Bathurst (N)
Forbes (N)
Bioassay data for four orchards where the number of moths treated exceeded 10 are
presented in Table 9. There were sufficient data from Rayner's to produce a dose
response line (Figure 2) which differed from the susceptible laboratory strain. However
we were unable to show a statistical difference between the lines.
For the three states combined, testing was possible for only 15 of the 23 orchards
surveyed. We were unable to diagnose azinphos-methyl resistance in adult codling moth
from any of these using the pheromone trap method.
The only orchard where survivors were observed at the DD (1.0 gac/L) was Rayner's
15
and this was prior to the decision to declare moths which moved claspers only as dead.
Some movement was observed in a few individuals but it is not clear from the laboratory
notes that only claspers were involved.
Table 9. Codling moth resistance survey - pooled results of bioassays on moths on
pheromone trap bases using 1 pL/ moth, control mortality disregarded
Location
Bathurst
Orange
Orchard
No. tests
Az-methyl
pooled
(gac/L)
treated
dead
Mort.
2
0.125
14
8
57
2
0.25
14
11
79
4
0.5
31
26
84
2
1.0
26
22
85
1
1.5
16
16
100
1
0.25
7
4
57
4
0.5
18
15
83
6
1.0
48
48
100
Leone
2
1.0
11
11
100
Shea
3
1.0
19
19
100
Rayner
Centofanri
Number moths
%
Overwintering larvae from the bands. When it became obvious that the pheromone trap
technique was not providing adequate data, trees on suspected resistant orchards were
banded in February-March 1992. Distribution of bands and the larvae yield are given in
Table 10. Where less bands were collected than were put on, birds or other animals
removed them. At BARS Bathurst, magpies destroyed the bands most likely while
seeking the overwintering larvae.
Recovery of adults from the bands range from 81% for Zorzi to < 23% for Reilly. The
reason for this is unknown. It may be associated with some variation in the storage time
and conditions.
Dose-mortality data were possible for four of the strains listed in Table 10. These are
given in Table 11. Corrected DD data for the 10 strains in Table 10 which yielded adults,
plus the Orange laboratory strain and moths which emerged from larvae ex fruit from
Pearce's orchard, Orange are presented in Figure 3.
New South Wales 1992193
Pheromone traps. Data were obtained from three orchards to further evaluate the
pheromone trap method as a resistance survey technique. Large numbers of moths were
taken (Table 12) and the maximum catches were:
Bathurst
26.10.92
169 moths in 40 traps
Forbes
28.10.92
172 moths in 40 traps
Orange
16.11.92
116 moths in 20 traps
16
99 .
Lab Strain
(S)
/
95.
(n=222)
90.
/
/
Rayner
(R?)
(n=85)
•*->
o 50.
•o
<D
*-»
O
•*
7
<D
k-
v.
O
O
10.
5.
oi
p
p
Ol
01
Azinphos methyl gac /L
Figure 2. Dose response lines for the orange laboratory strain (S) and the Rayner strain
(R?) using the pheromone trap bioassay technique. Rayner data are uncorrected for
control mortality
17
100
80
cc
t r 60 o
•o
t3
£
CD
40
O
O
20 --
Legend:
A - Orange laboratory strain, 134 moths treated (n)
B - Pearce, Orange, larvae ex fruit Feb 1992, n = 47
C - Gottschall, Orang, n = 18
D - Rayner, Bathurst, n = 70
E - Zorzi, Stanthorpe, n = 42
F - Harvey, Stanthorpe, n = 13
G - Reilly, Batlow, n = 29
H - Granite Belt HRS, Stanthorpe, n = 11 (uncorrected)
I - Galvin, Batlow, n = 10 (uncorrected)
J - Duffy, Batlow n = 25
K - Girot, Forbes, n = 62
L - Centofanti, Orange, n = 79
Figure 3. Corrected mortality of codling moth adults from 11 orchards and the Orange
laboratory strain, 1991/92. Moths were treated with 0.5 gac/L azinphos-methyl. Adults
were reared from larvae in cardboard bands (Table 10).
18
Table 10. Collection of diapausing codling moth larvae using cardboard bands in New
South Wales (N) and Queensland (Q), 1992
Location
Date bands
Length of bands (m) Number
On
Off
Attached Retrieved
BARS
24.3
24.6
72
Rayner
24.3
17.6
Duffy
21.2
Galvin
Orchard
Adults
larvae
emerged
0
0
0
72
67
71
30
25.5
50
50
69
44
21.2
25.5
50
50
22
10
Reilly
21.2
25.5
50
50
200+
45
Forbes (N)
Girot
20.2
5.6
50
50
312
245
Orange (N)
Centofanti
19.2
20.5
50
50
200+
247
Gottschall
27.2
12.6
50
50
40
21
McClymont
23.3
17.6
50
25
2
0
Offner
23.3
17.6
50
50
3
0
GBHRS
3.2
10.4
45
45
20
11
Harvey
28.2
14.5
40
40
122
73
Zorzi
28.2
7.5
30
30
180
145
Bathurst (N)
Batlow (N)
Stanthorpe (Q)
Dose-mortality data were generated for each of strains using data from the first
generation moths, October for Forbes, October-November for Bathurst and NovemberDecember for Orange (Table 13).
19
Table 11. Dose-mortality data for adults of four strains of codling moth from Orange (O),
Stanthorpe (S) and Forbes (F) reared from overwintered larvae compared with a
susceptible laboratory strain
Strain
(District)
n
gac/L
gac/L
Slope
RF
(LQo)
LaboratoryA
383
0.11
0.42
4.05
-
Harvey (S)
69
0.35
2.93
2.51
3.2
Zorzi (S)
164
0.45
1.58
4.26
4.1
Centofanti (0)
235
0.69
2.37
4.33
6.3
Girot (F)
245
0.70
5.88
2.52
6.4
A
See Table 7.
Table 12. Summary of codling moth captures in sex pheromone traps, October 1992 to
February 1993
Orchard
District
Number of
Total
Total
Moths per
nights
traps
moths
trap
Girot
Forbes
6
190
361
1.9
Rayner
Bathurst
7
179
489
2.7
Centofanti
Orange
9
168
471
2.8
537
1321
2.5
TOTALS
Table 13. Dose-mortality for three field strains and the laboratory strain of codling moth
using the pheromone trap technique, 1992
Strain
n
LCjo
Lt-99
gac/L
gac/L
Slope
RF
LCso
LaboratoryA
272
0.17
0.67
3.88
-
Girot
221
0.16
3.83
2.24
0.9
Rayner
442
0.17
2.91
1.87
1.0
Centofanti
273
0.30
5.88
1.80
1.8
A
Test date 15.12.92 using azinphos-methyl ex Israel.
20
The 95% confidence intervals (CIs) for the LC50 data in Table 13 were:
Laboratory
Girot
Rayner
Centofanti
0.15-0.19
0.13-0.25
0.13-0.21
0.23-0.39
The pheromone trap technique failed to diagnose resistance in the Girot and Rayner
strains, while the Centofanti strain was 1.8 x resistant (statistically significant as the CIs
did not overlap). Note that in the previous season, 1.0 gac/L killed 100% of the moths on
the bases ex Centofanti's (Table 9), yet in spring 1992, it took (statistically) 5.9 gac/L to
kill 99%.
Bioassay of adults reared from larvae. Fruit infested with larvae were collected from D
Gartrell's orchard in February 1993. As adults emerged they were treated and the results,
Table 14, indicate resistance.
Table 14. Mortality of adult codling moths treated with 0.5 gac/L (D Gartrell, Orange, ex
infested fruit, 1993)
Treatment
Treated
Dead
Control
3
0
Azinphos-methyl
26
11
Corr. morL (%)
42.3
Bands were placed on trees in seven orchards in February 1993, and diapaused larvae
and pupae were collected from Selwood's orchard, Orange in early November 1993.
Results from testing adults are in Table 15 and illustrated as corrected mortality at 0.5
gac/L in Figure 4.
Larval challenge
The statistics obtained in the dose-mortality experiments in 1991/92 are given in Table
16.
Both sets of data (tests undertaken two weeks apart) are in general agreement - the IXZ^
and LQ, are 1.3 and 1.2 x higher in the second set than the first set respectively. Table
17 compares the laboratory strain and larvae from Bathurst Agricultural Research Station
(BARS).
The LCJQ obtained for the laboratory strain (Table 17) falls midway between those
given in Table 16. The LQ, for the laboratory strain in Table 17 is higher than those in
Table 16 but confidence intervals are very wide and statistically, the difference would not
be significant. From these data we have chosen an LCJQ of 0.008 gac/L and an LC,, of
0.12 gac/L to use as a 50% mortality and DD respectively for testing larvae for resistance.
The BARS strain showed a similar response to the laboratory strain. We were unable
to satisfactorily test any other strains.
21
Table 14. Mortality of codling moth collected from orchards in New South Wales,
February to November 1993
Strain,
location
Az-methyl
(gac/L)
Number
tested
Mortality
(%)
Corrected
mortality (%)
Laboratory
0 (control)
0.5
35
46
2.9
91.3
91.0
0
0.5
27
63
14.8
76.2
72.1
Centofanti, Orange
0.5
26
53.8
-
C Culverson, Orange
0
0.5
64
72
9.4
69.4
66.2
0
0.5
1.0
3
15
3
0
46.7
66.7
46.7
66.7
0
0.5
1.0
1.5
47
63
26
12
0
22.2
14.0
91.7
22.2
14.0
91.7
0
0.5
1.0
1.5
57
84
6
6
5.3
60.7
100.0
100.0
58.5
100.0
100.0
0.5
29
93.1
-
ARS, Bathurst
Dally, Orange
Girot, Forbes
Reilly, Batlow
Selwood, Orange
Table 16. Dose-mortality statistics for azinphos-methyl against codling moth larvae from
the Orange laboratory strain
Treatment range
n
(x 10"3 gac/L)
1.95 - 31.5
1.0 - 30.0
600
600
LCjo
LC^
Slope
(95% CD
(95% CI)
(±SE)
7.08 x 10'3
96.8 x 10"3
2.05
(6.11-8.19)
(63.3-148.1)
(0.36)
9.13 x 10"3
114.1 x 103
2.82
(8.09-10.3)
(77.3-168.3)
(0.25)
22
100
Legend:
A - Laboratory strain, n = 46
B - Selwood, Orange, 29 moths treated (uncorrected)
C - ARS Bathurst, n = 63
D - C Culverson, Orange, n = 72
E - Reilly, Batlow, n = 84
F - Centofanti, Orange, n = 26 (uncorrected)
G - Laurie, Stanthorpe, n = 39
H - Dally, Orange, n = 15
I - Gartrell, Orange, larvae ex fruit Feb 1993, n = 26
J - Volpato, Stanthorpe, n = 27
K - Costanzo, Stanthorpe, larvae ex fruit Feb 1993, n = 14
L - Girot, Forbes, n = 63
Figure 4. Corrected mortality of codling moth adults from 11 orchards and the Orange
laboratory strain, 1992/93. Moths were treated with 0.5 gac/L azinphos-methyl. See also
Tables 5, 14 and 15.
23
Table 17. Dose-mortality statistics for larvae from BARS strain and the Orange laboratory
strain
Strain
BARS
Laboratory
n
250
250
L.U50
L>V^99
Slope
(95% CI)
(95% CI)
(±SE)
9.80 x 10-3
117.2 x 10°
2.16
(7.69-12.50)
(48.3-284.3)
(0.44)
8.01 x 103
192 x 10-3
1.69
(5.97-10.75)
(55.6-666.9)
(0.72)
Discussion
Our results clearly show that codling moth is resistant to azinphos-methyl in apple
orchards in eastern mainland Australia and that the resistance varies from orchard to
orchard within a district. The highest level of resistance we could document was 6.3 x
and 6.4 x for Centofanti and Girot respectively (Table 11). Both these growers have
experienced considerable difficulty in controlling the pest. It is also apparent that almost
all of the growers who complained about inadequate control from azinphos-methyl were
justified in doing so - even low level resistance makes control difficult.
We set out to evaluate a simple method for detecting resistance in codling moth which
had been developed in the USA by Riedl et al. (1986). They pointed out the limitations
of topical application of moths reared from larvae in fruit or collected from overwintering
cocoons in detecting low frequencies of resistant individuals. Varela and Welter (1990)
used the technique to confirm codling moth resistance to azinphos-methyl in California.
They subsequently participated in a survey of four western states where they demonstrated
the value of the traps in detecting resistance (Varela et al. 1993).
In the first season of this project, a total of 48 separate trapping operations in 23
orchards in New South Wales, Queensland and Victoria were carried out on 28 nights
from early November 1991 to early March 1992 (Table 8). Catches were disappointingly
low, with only 436 moths taken in 460 traps over the four months. Welter (pers. comm.)
pointed out that low moth catches in commercially managed orchards limited the scope of
pheromone traps for resistance survey, although Knight et al. (1991) suggest that
insecticide resistance is not a problem in orchards with low density populations of codling
moth.
By the end of 1992, it became obvious that the sex pheromone trap technique was not
sufficiently sensitive to detect resistance under our conditions.
Figure 5 summarises the data obtained from Girot's orchard at Forbes. Resistance was
demonstrated in tests conducted on the adults which emerged from larvae which had
diapause artificially broken (5a). When the same strain of adults emerged naturally and
were taken in pheromone traps, resistance could not be detected (5b).
We have no satisfactory explanation for this. Until a rapid diagnostic test is developed,
identification of resistance will continue to be a slow laborious process.
24
991
99n
riAB
9590-
80-
£lROT
95-
GIROT/
/
/
/
/
/o
80
/
2 50-^
o
o
3.
O/
/
20
20H
105-
I J
—i
0.05
r0.1
0.2
—r~
0.4
Dose
—J—
0.8
1.6
i
0.1
•
i
'
0.2
i
0.4
Dose
0.8
Figure 5. Dose-mortality lines for codling moth (a) emerged from cardboard bands (Girot
strain) compared with the susceptible laboratory strain (resistance factor 6.8 x) and (b) the
same strains bioassayed while stuck to sex pheromone traps.
25
Field control
During 1991/92, reports were received from numerous growers about poor control of
codling moth. In some cases, it was confined to one or two blocks (examples - H and J
Gottschall, W Culverson, R Pearce - Orange, L Harvey - Cottonvale) and in other cases
most of the orchard (examples - G Centofanti, C Culverson - Orange, H Rayner Bathurst, G Zorzi - Cottonvale).
At CentofantTs a program of eight azinphos-methyl sprays were applied from 11
November 1991 to 28 February 1992. There is no estimate of damage at harvest but
during the season at least 10 visits were made to the orchard and codling moth infestation
was readily observed. The overwinter bands yielded a large number of larvae which,
when tested as adults, the population was found to be resistant. Damage was again
observed in 1992/93.
The first orchard in Australia in which resistance was detected (Durham, Bacchus
Marsh, 1991) was subjected to a more intensive control schedule in 1991/92 man
previously. The grower shortened spray intervals for azinphos-methyl to 14 days early in
the season to target the first generation. Spray intervals for the second and third
generations varied according to pheromone trap catches (Figure 6). A total of nine
insecticides were applied, seven azinphos-methyl an done each of chlorpyrifos and
phosmet at a total cost of $916/ha. Codling moth damage at harvest was less than 0.2% at
the end of the season.
A
per Trap
CO
35
JC
•
60
55
C A
mini \
65 ,
K
A
»
-
50 ••
45 ••
40 •-
-
30 25 -
m
20 •
o
15 -
JQ
10 -
E
5 -
3
z
I
6»
i
1
a£
i
LEp.
_£pU
rapagi^PHmMm
30-09 14-10 28-10 11-11 25-11 09-12 23-12 06-01 20-01 03-02 17-02 02-03 16-03 30-03
1991-92
Figure 6. Codling moth catches in pheromone traps at Durham's, Bacchus Marsh
1991/92. The insecticide schedule is also shown: A - azinphos-methyl (Gusathion® ); C chlorpyrifos (Lorsban® ); P - phosmet (Imidan® ). Damage - 0.2% at harvest.
26
Not all cases of poor control can be blamed on resistance. Application timing and
techniques are also important. For example, damage at the Pearce orchard in 1991/92 was
attributed to a mistimed application - there was no resistance (Figure 3). Likewise,
Selwood's blame problems with their spray equipment for poor control - resistance was
not detected in moths from that orchard (Figure 4).
Conclusions
1. A disturbing number of apple and pear growers in Queensland, New South Wales and
Victoria are experiencing problems in controlling codling moth despite the use of a
season program of sprays of azinphos-methyl.
2. Resistance has been confirmed in orchards in Queensland and New South Wales. It is
also strongly suspected in Victoria but needs to be confirmed through dose-mortality
tests.
3. The use of sex pheromone traps as a resistance survey device have not provided the
data expected and a less time consuming technique for diagnosing resistance is
required.
4. There is an urgent need to establish a resistance management strategy to enable the
industry to cope with the existing resistance situation and to try to delay the onset of
resistance in other orchards.
Acknowledgments
The authors thank Mr Stephen Sexton, Biocontrol Limited, Warwick, who has assisted
the project in many ways. Cooperating growers allowed us unrestricted access to their
properties. Anne Hately and Marion Eslick provided valuable technical assistance.
Several colleagues have advised on the analysis and interpretation of the dose response
data. Maree Graham prepared the report for reproduction.
This project was financed by several fruitgrower's organisations in Victoria and New
South Wales and agricultural chemical companies through AVCA's AIRAC, with an equal
contribution from the Horticultural Research and Development Corporation. We thank Mr
Ian Anderson, Chairman of AIRAC, for his encouragement and support.
27
References
Abbot, W (1925) - A method for comparing the effectiveness of an insecticide. Journal of
Economic Entomology 18: 265-267.
Barnes, M M, Wargo, M J and Baldwin, R L (1965) - New low intensity ultraviolet light
trap for detection of codling moth activity. California Agriculture 19(10): 6-7.
Croft, B A (1982) - Arthropod resistance to insecticides: a key to pest control failures and
successes in North American apple orchards. Entomologia Experimentalis et Applicata
31: 88-110.
Croft, B A and Riedl, H W (1991) - Chemical control and resistance to pesticides of the
codling moth. Chapter 5.1.5 in Tortricid Pests: Their Biology, Natural Enemies and
Control - L P S van der Geest and H M Evenhuis (Eds). Elsevier. 371-387.
Geier, P W (1981) - The codling moth, Cydia pomonella (L): profile of a key pest
Chapter 6 The Ecology of Pests - Some Australian Case Histories - Kitching, R L and
Jones, R E (Eds). CSIRO Australia. 109-129.
Knight, A L, Brunner J and Wildman, T (1991) - Monitoring Guthion resistance in codling
moth. Proceedings 8th Annual Meeting, Washington State Horticultural Association.
226-227.
Lloyd, N C (1960) - The codling moth: recent developments in its control. Agricultural
Gazette of New South Wales 71: 35-40, 51.
Morris, D S and Van Baer, R (1959) - DDT-resistant codling moth in Victoria: laboratory
and field investigations with insecticides. Journal of Agriculture, Victoria 57: 619-623,
684-687.
Riedl, H, Hanson, L A and Seaman, A (1986) - Toxicological response of codling moth
(Lepidoptera: Tortricidae) populations from California and New York to
azinphos-methyl. Agriculture, Ecosystems and Environment 16: 189-201.
Riedl, H, Seaman, A and Henrie, F (1985) - Monitoring susceptibility to azinphos-methyl
in field populations of the codling moth (Lepidoptera: Torticidae) with pheromone traps.
Journal of Economic Entomology 78: 692-699.
Thwaite, W G (1978) - Integrated pest control in apples: The migration and dispersal of
codling moth, Cydia pomonella (Linnaeus) in a Bathurst NSW orchard. University of
NSW. MSc Thesis. 99pp.
Thwaite, W G (1984) - Laboratory evaluation of insecticides for the control of codling
moth, Cydia pomonella (L.) in apples.
Proceedings 4th Australian Applied
Entomological Research Conference. Adelaide. 238-243.
Thwaite, W G (1985) - Failure of chlorthiophos to protect apples from attack by Cydia
pomonella (L.). General and Applied Entomology 17: 54-56.
Thwaite, W G (1990) - Report on an official visit to the United States of America,
September 1990. NSW Agriculture. 8-10 and Appendix 6.
Varela, L and Welter, S C (1990) - Codling moth resistance in pear orchards in California.
Research Reports: 64th Annual Western Orchard Pest and Disease Management
Conference. Portland Oregon USA: 40-41.
Varela, L G, Welter, S C, Jones, V P, Brunner, J F and Riedl, H (1993) - Monitoring and
characterization of insecticide resistance in codling moth (Lepidoptera: Tortricidae) in
four western states. Journal of Economic Entomology 86: 1-10.
28
APPENDIX 1
List of Cooperators
Queensland
Stanthorpe district
W and G Calvesi, Cottonvale Q 4375
G Costanzo, Ridge Road, The Summit Q 4377
Granite Belt Horticultural Research Station, PO Box 501, Stanthorpe Q 4380
L Harvey, Old Warwick Road, Cottonvale Q 4375
Sun Star Fruit Pty Ltd, Newlands Road, Cottonvale Q 4375
A and W Volpato, Newlands Road, Cottonvale Q 4375
G Zorzi, PO Box 15, Cottonvale Q 4375
New South Wales
Bathurst
Bathurst Agricultural Research Station, Bathurst NSW 2795
H and L Rayner, "Appleton", College Road, Bathurst NSW 2795
Batlow (Willigobung)
C N and E Cook, RMB 607, Tumbarumba NSW 2653
J and K Duffy, PO Box 151, Tumbarumba NSW 2653
G Galvin, Adelong Road, Tumbarumba NSW 2653
C and D Reilly, "Binnawie", South Spur Road, Tumbarumba NSW 2653
Forbes
H and B Betland, Salisbury Road, Forbes NSW 2871
N and K Girot, PO Box 135, Forbes NSW 2871
N and D Hurkett, Wandary Lane, Forbes NSW 2871
Orange district
G Centofanti, "Golden Way", Clergate NSW 2800
C Culverson, "Hillview", Clergate NSW 2800
W Culverson, "Heatherdale", March NSW 2800
D Gartrell, "Pentridge", Ploughmans Lane, Orange NSW 2800
H and J Gottschall, 21 Cadia Road, Orange NSW 2800
J Leone, (Hazelhome orchard), PO Box .Orange NSW 2800
R and J McClymont, "Failford", Springside NSW 2800
R Pearce, "Mirrabooka", Ophir Road, Orange NSW 2800
G Selwood, "Hillcrest", Cadia Road, Springside NSW 2800
V and M Shea, "Mount Olive", Forest Reefs NSW 2798
Victoria
Bacchus Marsh
J Durham, (Woolpack Road orchard) Mason's Road, Bacchus Marsh Vic 3340
Shepparton
R Clements, Clements Road, Toolamba Vic 3614
A Prentice, Prentice Road, Shepparton East Vic 3631
R Webb, (Toolamba Road orchard) Channel Road, Shepparton East, Vic 3631
30
APPENDIX 2
List of Contributors
Grower Organisations
Eastern Metropolitan Fruitgrowers' Association
Harcourt and District Fruitgrowers' Association
NSW Farmers' Association - Orange Fruit Branch
Orchardists' and Fruit Cool Stores Association of Victoria
Member companies, AVCA
Bayer Australia Ltd
Colin Campbell (Chemicals) Pty Ltd
Incitec Ltd
Koor Intertrade Pty Ltd
Rohm and Haas Australia Pty Ltd
Wellcome Australia Limited
Horticultural Research & Development Corporation
31
APPENDIX 3
List of Publications
The following articles are included with this report.
Extension
• Codling moth; is there resistance to azinphos-methyl in your orchard? W G Thwaite,
Fruitwise No 8, 1992 p 10.
• Resistance to azinphos-methyl in codling moth. Graham Thwaite, Fruitwise No 11,
1992 pp 2-4.
• Azinphos-methyl: is codling moth failing? Graham Thwaite, Fruitwise No 15, 1993 pp
4-5.
• Codling moth: back after 35 years. Graham Thwaite, Good Fruit & Vegetables Vol 3
No 11, 1993 p 31.
Research
Thwaite, W G, Williams, D G and Hately, A M (1993). Extent and significance of
azinphos-methyl resistance in codling moth in Australia. Pest Control & Sustainable
Agriculture, CSIRO Australia: 166-168.
RESISTANCE TO
AZINPHOS-METHYL IN
CODLING MOTH
Graham Thwaite,
Senior Entomologist
AR&VC
Orange
In previous issues of Fruitwise I have mentioned
the discovery of resistance to azinphos-methyl in
codling moth in Australia. The first confirmed case
was at Stanthorpe, Queensland. There is also some
evidence ofresistance from two orchards in southern
Victoria.
1991/92 resistance survey
A survey of codling moth adults using sex
pheramone traps failed to detect any resistance in
20 orchards at Bathurst, Badow, Forbes, Orange or
Stanthorpe. In addition to trapping, where possible
infested fruit was collectedfromwhich adult moths
were reared for testing. Later, cardboard bands
were placed around trees to collect overwintering
larvae.
Adults are still emerging from these bands and
testing is in progress, but the results are at last
making the resistance situation clearer. Resistant
codling moth has now been found at a second
orchard at Stanthorpe and one at Badiurst.
Codling moth had been a problem on two orchards
in 1990/91 and modis had tested as being suspected
resistant in July 1991. Through close attention to
application techniques in 1991/92, moth damage in
these orchards was negligible.
Similarly in New South Wales, some growers with
a codling moth problem observed that infestation
was greatest on older, dense trees. Elsewhere on the
same orchard, smaller trees had little damage. S pray
coverage is the key to more successful control
Azinphos-methyl still effective
The majority of apple and pear growers in the main
districts still achieve satisfactory control with
azinphos-methyl despite its continued use for more
than 30 years. However in some orchards, control
is on a knife-edge - get everything right and there
will be few problems. Miss a critical spray or fail
to get adequate cover and moths are there waiting to
infest the fruit.
Why these factors should be so critical now
compared, say, with 10-15 years ago remains
unexplained. What we do know now is that
resistance has arrived, albeit in the very early stages.
Application techniques important
The levels of resistance identified are quite low and
seem to be associated with application difficulties.
The low resistance factor can't really account for
the sometimes heavy infestation in fruit. This
conclusion is supported by the situation in Victoria.
Growers who suspects that they have a control
problem should contact the local district
horticulturist or phone Graham Thwaite on (063)
913821
FRUITWISE Spring 1992 No. 11 pp 3-4. NSW Agriculture, Orange
laboratory tests at Orange on a sample of
the pest collected from Stanthorpc
(Queensland) revealed a resistance level
in adults of 2.5 times. A similar level of
resistance is also suspected from an
orchard in southern Victoria and recent
tests suggest that a Bathurst orchard may
also be in difficulty.
Resistance Monitoring
A project to find out if there is resistance
and where, is under way in New South
Wales and Victoria.
CODLING MOTH: IS
THERE RESISTANCE
TO AZINPHOSMETHYL IN YOUR
ORCHARD?
Subject to approval from the
Horticultural Research and Development
Corporation, the work will be financed
by contributions from grower groups and
agricultural chemical companies matched
dollar for dollar by the Corporation.
Orange Fruitgrowers R&D Committee
has decided to assist with funding.
W. G. Thwaite
Senior Entomologist
AR&VC ORANGE
The testing technique involves catching
codling moths in sex pheromone traps
and treating them with insecticide. Light
trapping and tree banding (to collect
larvae) will also be used. Monitoring
will take place in all major districts as
time and weather conditions permit.
In winter 1991 the first case in Australia
of resistance to azinphos-methyl in
codling moth was confirmed. Azinphosmethyl, sold under the trade names
Gusathion® Benthion® and Azithion®,
has been in use for 30 years and during
that time has provided the apple and pear
industry with protection from its most
destructive pest.
Any apple grower who is having
problems with codling moth control and
who is interested in having moths tested
for resistance should advise their District
Horticulturist. Alternatively, phone
Graham Thwaite or Anne Hately at the
Agricultural Research and Veterinary
Centre, Orange, on (063) 63 6700. Leave
a message if they are unavailable or fax
details to them on (063) 63 6799.
A small number of growers in different
parts of the state and at different times
over the last decade have experienced
problems with control of codling moth.
This has usually resulted in more sprays
being applied. Often attention to spray
application technique has overcome the
lapse in control. However there has
always been a few orchards which seem
to consistently have difficulty and
resistance to the pesticide has been one
possible explanation.
FRUITWISE No. 8
Summer 1992
NSW Agriculture
Until last year, resistance had not been
detected in Australia. However
10
FRUIT
V c l . 3 Mo.W
CODLING MOTH
Gc-od Fruit t V«-a*UM«
Aprtl 1 « 3
Jl
Codling moth: back
after 35 years
By GRAHAM THWAITE
Apple and pear growers in southeastern Australia have a new
problem to contend with —
insecticide resistance in codling
moth.
Codling moth is the most
destructive pest of pome fruit and
if not adequately controlled, can
result in heavy fruit loss.
Entomologists in NSW and
been reduced to a few including
Azithion. Benthion and Minchem
azinphos-methyl in addition to
Gusathion.
First resistance signs
As early as the mid 1970s, some
apple growers reported they were
not achieving the same control of
codling moth with azinpbosmethyl they did previously,
At that time, experimental evi-
In July 1991, Victorian Department of Agriculture's Institute of
Plant Sciences senior entomologist
at Burnley. David Williams, tested
some codling moths from an
orchard in Victoria which had
experienced a serious problem
with control in 1990/91.
His results suggested the first
sign of resistance in Australia.
Meanwhile, codling moth from
an orchard in Queensland's Graham Tawaite checks overnight catches la a sex pberomooe trap before testis
Sunthorpe district — where simi- the nom for resistance to sxtophos •ethyl
lar problems were experienced —
was tested at Orange.
This strain was confirmed to
have a resistance level of two to
three limes.
While this is quite low compared
with resitances found in other
pests, it nevertheless signalled a
potential problem for pome
fruitgrowers in Australia.
Resistance survey
Based on these two findings.
David Williams and myself approached the manufacturers of
azinphos-methyl for financial support to continue their investigations.
The Horticultural Research and
The damage caused by the feeding of a codling modi larva can be seen Development Corporation match- Cokting moth larva.
when an apple is cut in half.
ed the grant and for the past two
Victoria have been investigating dence highlighted problems with seasons, work has been carried
some recent control failures and application techniques and when out in Queensland, NSW and
they now believe the pest has these were addressed, complaints Victoria to try to understand the
present resistance situation.
developed resistance to growers' subsided.
The Americans have based
main weapon against it —
A decade later, growers again
azinphos-methyl.
drew attention to problems they much of their research on a
Fruit damage is caused by the were having with codling moth technique which involves capturlarval, or caterpillar, stage of the control, many claiming they need- ing moths in sex pheromone
ed to shorten the spray intervals traps and treating them with
insect.
The young larva hatches from required from 28 days to around insecticide while the adults are
still on the sticky base.
an egg laid on or near the fruit 14 days.
This has been tried extensively
and quickly chews a hole through
Resistance in the pest to the
through the three Australian
the skin and tunnels it ways
states and so far has not
to the core.
provided
any worthwhile inWhen feeding is completed,
formation on resistance.
the now much bigger caterpillar makes a second tunnel to
However, collecting larvae
the outside of the fruit and
in corrugated cardboard
forms a cocoon somewhere
bands in autumn and testing
on the tree.
the moths which emerge has
been far more revealing.
A moth will later emerge
The larvae, having comfrom the cocoon.
pleted development in the
There are two to three
fruit, move down the tree
generations a year on the
and overwinter under rough
mainland and one in Tasmabark on the trunk and lower
nia, where the pest is less of
branches.
a problem.
Attaching bands of corruInsecticide cover sprays ate
gated cardboard on the trunk
needed to prevent the damage
captures some of these overit causes.
wintering caterpillars — and
Azinphos-methyl. when apthese can then be reared to
plied as a regular schedule of
adults.
four to eight sprays a season
between
November and
Resistance levels of up to
March, protects the fruit
seven times have been detectfrom attack by the newly
ed from orchards in several
hatched larvae.
Aa adult codliag moth emerges from . districts of Queensland and
NSW.
It will also kill eggs about cocoon me larva has made on the tree.
Bands have been applied
to hatch as well as adults
which come into direct contact chemical was one obvious expla- to trees again this autumn to
with the chemical.
nation. but testing could not further survey for resistance.
So far, the resistance to
Azinphos-methyl. an organo- show that resistance occurred in
azinphos-methyl has not meant
phosphate insecticide, was first NSW.
total
control failure, but it has
A
similar
pattern
was
emerging
used as Gusathion in 1958 in
trials to overcome resistance to overseas, and despite extensive made control harder and more
expensive.
testing, resistance to azinphosDDT
had not been found by
For 35 years, azinphos-methyl
The DDT chemical had been methyl
has generally given excellent proused so successfully for the previ- 1988.
This situation changed in 1989 tection of fruit from codling
ous decade against the moth.
when American scientists Stephen moth attack and so far no other
Gusathion became widely avail* Welter and Lucia Varela detected chemical has been able to achieve
able in 1959/60 and has been insecticide resistance in codling this level of control at a comparused in Australian apple and pear moth in a Califomian pear or- able cost.
orchards ever since.
chard.
The entomologists researching
The work has continued and this problem for the po*ne fruit
Other
insecticides.
both
organophosphates and carba- resistance has now been discovered industry have yet to develop a
mates (such as carbaryly were in other parts of the America.
strategy lo help growers through
;IIM> introduced 10 replace DDT.
The author discussed the first this latest problem.
but the effectiveness of a/inphos- incidence of resistance with ProDuring the 1993 winter, the
mcthyl under a wide range of
fessor Welter and Dr Varela in
options will be discussed with
condition-. and Us v.iluc in inte- California in I'WO. and studied
agricultural chemical industry repgrated mile control programs has the detection method they had
resentatives and growers will be
made it the industry standard.
developed in collaboration with
informed of ihc outcome before
During (he past
ts
years.
a/inphox-niethvl has Iven available lo growers under mans trade
name-.
I".1.t\. howc-er. the ranee has
other American entomologists
There was a striking similarity
between the » j \ the control
problems emeiecd in America
and m AtisU.ilia
next season
(irnhjm
Thw:nlc is J senior
••/ifomo/oeisl Mi/h .Vi'Vt' Agriculture bjxrd jf Oranee. . W i t '
Extent and Significance of Azinphos-Methyl
Resistance in Codling Moth in Australia
W.G. Thwaite1, D.G. Williams2 and A.M. Hately1
'NSW Agriculture, Agriculture Research & Veterinary Centre
Forest Road, Orange, NSW, 2800, Australia
^Department of Agriculture, Institute of Plant Sciences
Swan Street, Burnley, Victoria, 3121, Australia
Introduction
Materials and Methods
Codling moth, Cydia pomonella (L) (Lepidoptera : All bioassays reported here were conducted on adult
Tortricidae) is potentially the most destructive pest of codling moths using an Arnold hand microapplicator
apples and pears in south-eastern Australia. Fruitgrowers (Burkard, UK).
A 1 ml droplet of azinphos-methyl technical grade
rely on a program of insecticide cover sprays to prevent or
minimise infestation. There are no significant natural (Bayer Australia Limited) in ethyl methyl ketone (EMK)
enemies of the pest in Australia, and while non-chemical was deposited on the dorsal thorax of the moth.
means of control are being researched, none has yet been Experimental controls were treated with solvent only.
Prior to treatment, moths which were not otherwise
shown to approach the level of protection that the industry
immobilised were anaesthetised using carbon dioxide.
has come to expect from the cover spray program.
Following treatment they were held in controlled
DDT was the first synthetic insecticide introduced into environment conditions (26°C, 55% RH, constant light)
commercial pome fruit orchards (1945-46) and for ten for 24 hours before mortality was assessed, unless
years gave outstanding control. Resistance to DDT in omerwise specified.
codling moth first appeared in 1956-57 and became
widespread by 1958-59, after which the organophosphate Determination of Discriminating Dose (DD)
(OP) insecticides rapidly replaced DDT (Morris & Van
Bioassays of some field collected strains were compared
Baer, 1959; Lloyd, I960).
with similar tests on a known susceptible strain reared in
One of the first OP's to be evaluated and subsequently culture at Orange. Specific experiments using the
recommended was azinphos-methyl (Gusathion*). In the laboratory strain established dose-mortality statistics for
34 years since it was first available azinphos-methyl has free flying moths and for those attached to sticky bases
been marketed by several companies, and remains the (see below). Where appropriate, mortality data were
industry standard for codling moth control. However, corrected with Abbott's formula and subjected to probit
during the last 10-15 years there has been an analysis. The statistics obtained were used to establish
undercurrent of discontent among pomefruit growers DDs for each method of resistance diagnosis.
concerning the effectiveness of azinphos-methyl. Many of
Field stains of codling moths were obtained for testing .in
the apparent control failures have been investigated. two different ways. Some emerged from material collected
Attention to spray application techniques and spray during winter 1991, either from artificial cocooning sites
timing has generally improved the effectiveness of (consisting of corrugated cardboard strips around the trunk
and main limbs of the tree), or from natural cocooning sites
azinphos-methyl in the problem orchards, but in a small
under bark on the trunk. Moths were treated within three
number, control has continued to be unsatisfactory.
days of emergence. This method is consistent with that
The possibility that resistance to azinphos-methyl
recommended by the FAO (Anon, 1974).
might occur in Australia has been considered but, prior to
The second method involved trapping males in the
1991, there was no evidence of this in any of the
field using sex pheromone traps (similar to Pherocon II),
populations tested CThwaite, unpublished). The first cases and treating the live moths adhering to the base
of suspected resistance were detected from Bacchus (Riedl et al., 1985). The cardboard bases (226 x 278 mm)
Marsh (southern Victoria) and Stanthorpe (Queensland) were prepared by marking a 20 x 20 mm grid over an
in winter 1991. This paper reports those findings and
area of 120 x 240 mm in the middle of the base, and
describes investigations to determine the extent of covering it lightly with Tangletrap* (The Tanglefoot
resistance in Queensland and New South Wales.
Company, Michigan, USA). Commercially prepared
166
Pest Control & Sustainable Agriculture, CSLRO Australia 1993, 166-168
EXTENT AND SIGNIFICANCE OF AZIN?HOS-M ETHYL RESISTANCE IN COOUNC MOTH IN AUSTRALIA
pheromone lures were used as the attractant. Traps were
placed in the field at a variable density in mid- to lateafternoon, removed later the same night or early the next
day, then treated. With one exception, the orchards used
were known to have had a codling moth control problem
in recent seasons.
Results
Emerged Motbs
Two strains of codling moth from Bacchus Marsh were
treated using a DD of 0.4 g a.c/1 in acetone (D.S. Morris,
unpublished); results are presented in Table 1.
A total of 29 moths which emerged from overwintering
shelter taken from the Rayner orchard, Bathurst, were
treated with 0.5 g a.c/1 azinphos-methyl. There were no
controls. Twenty moths (69%) died after 24 hours.
Determination of Discriminating Doses
Table 2 compares the statistics generated from dosemortality tests on the OP susceptible laboratory strain for
both the standard bioassay and moths adhered to the trap
bases. Using the LC,,, DDs were established as 0.5 g ac/1
and 1.0 g ac/1 for free flying and attached moths
respectively.
Moths which originated from the Zorzi orchard. Cotton
Vale, Queensland, were compared with the susceptible
laboratory strain in a dose-mortality experiment. The
results are given in Table 3.
Pberomone Traps
Traps were placed in a total of 19 orchards in New South
Wales and Queensland. There were 45 separate trapping
operations during 27 nights from November 1991 to
February 1992. A toul of 443 traps caught 433 moths
(0.98 moths/trap/night). Six of the orchards did not yield
adequate catches to provide meaningful data. Treatment
of moths captured at the remaining orchards showed no
evidence of resistance at any site.
Discussion
Croft (1982) stated that no cases of resistance to
azinphos-methyl in codling moth had been reported in
the world, despite 2 0 - 3 0 years of its use in some apple
and pear orchards. Reidl et at., (1986) documented some
control failures in the USA but were unable to identify
resistance. Varela & Welter (1990) first diagnosed low
levels of resistance in California in 1989.
Our data clearly demonstrate that resistance to
azinphos-methyl in codling moth has now appeared in
Australia. Low level resistance is present in the Zorzi
population (Table 3); this orchard remains the only one
for which we have confirmation. There are some minor
differences in the dose-mortality statistics for the Orange
laboratory strain in Tables 2 and 3. This variation is most
probably related to the smaller number of individuals
tested in the strain comparison experiment (Table 3)
Table 1 Mortality1 of codling moth adults from two Bacchus
Marsh (Victoria) apple orchards, 1991
Treatment
Durham strain
Dcllos strain
No. tested No. dead No. tested No. dead
Az-methyl
0.4 g a.c/1.1
Control (acetone)
Corr. mort. (%)
1
20
4
21
5
6
1
4.0
10
0
23.8
After 48 hours at 25*C
* Solvent was acetone
Table 2 Effect of azinphos-methyl on susceptible laboratory
strain codling moth adults in a standard bioassay, and on
pheromone trap bases
Method
n
IX^,
(95% CO
IC„
(95% CD
Slope
Standard
383
(mobile moths)
0.11 g a.c/1
(0.10-0.12)
0.42 g a.c/1
(0.32-0.54)
4.05
(±0.45)
Moths adhered
to trap base
0.17ga.c/l
(0.15-0.20)
0.86ga.crt
(0.57-1.31)
3.34
Ct 0.33)
257
Tabic 3 Dose-mortality data for azinphos-methyl against two
strains of codling moth in 1991, with resistance factors (RF)
Statistic
Strain
ARVCbb
(susceptible)
Zorzi Qld
(resistant)
(95% CD
0.19 g a.c/1
(0.15-0.23)
0.48 g a.c/1
(0.27-0.84)
LC„
(95% a )
0.35 g a.c/1
(0.28-0.44)
2.53 g a.c/1
(0.87-7.40)
5.9 (± 0.5)
2.3 (± 1.1)
100
100
Slope (± SE)
n
The Bacchus Marsh finding (Table 1) is based on an
historical DD. According to recent data obtained at Orange
(Tables 2 and 3), the LC,,, for the laboratory susceptible
strain is 0.1-0.2 g a.cA Rose & Hooper (1969) determined
a similar LC,,,, and also noted Morris" LC^, of 0.09 g a.cA
Therefore it is reasonable to expect 0.4 g a.c/1 to kill more
than 50% of the moths, although perhaps less than 100%.
The Orange LC„ was 0.42 g a.c/1 (Tables 2 and 3). and
Rose & Hooper (1969) quoted their LC,, as 0.29-0.42 g
a.cA The limited data available from the Bacchus Marsh
strains (Table 1) has mortality well below 50%, and there is
thus a strong probability that resistance is present. Dosemortality lines are now required to confirm this.
Despite a regular cover spray program, Rayner's
orchard has a serious codling moth problem. Tests on the
few moths which emerged from overwintering shelter
were inconclusive, and treatment of a toul of 170 moths
taken in pheromone traps at this orchard failed to
provide evidence of resistance. The extent of the
problem there justifies further investigation.
PEST CONTROL AND SUSTAINABLE AGMCULTUKE
Croft, B.A. (1982) Arthropod resistance to insecticides: a key
to pest control failures and successes in North American
Some of the data presented are based on small numbers of
apple orchards. Entomologia Experimentalls et Applicata
moths, and the conclusions drawn can at best be tentative.
31:88-110.
However they do give some indication of the codling moth
Uoyd, N.C (1960) The codling moth: recent developments in its
resistance situation in the three eastern mainland states.
control. Agricultural Gazette ofNew South Wales 71:35-40, 51.
Methods for diagnosis and confirmation of azinphosMorris, D.S. & Van Baer, R. (1959) DDT-resistant codling moth in
methyd resistance in codling moth have been evaluated,
Victoria: laboratory and field investigations with insecticides.
and will be used for a more extensive survey of pome
Journal ofAgriculture, Victoria 57:619-623,684-687.
fruit orchards in Queensland, New South Wales and
Riedl, H., Hanson, L.A. & Seaman, A. (1986) Toxicological
Victoria in 1992-93- We have established that resistance to
response of codling moth (Lepidoptera : Tortrlcidae)
azinphos-methyt has appeared in Australia. However, the
populations from California and New York to
reasons for unsatisfactory control of the pest in at least
aztnphosmeuiyt. Agriculture, Ecosystems and Environment
parts of many other orchards continue to elude us.
16:189-201.
Riedl,
H., Seaman, A. & Henric, F. (1985) Monitoring
Acknowledgements
susceptibility to xzinphosmethyi in Held populations of the
codling moui (Lepidoptera : Tortricidae) with pheromone
This work has been supported by Victorian and New South
traps. Journal ofEconomic Entomology 78: 692-699.
Wales pome fruit growers with matching funding from the
Horticultural Research and Development Corporation.
Rose, H.A. & Hooper, G.H.S. (1969) The susceptibility to
insecticides of Cydla pomonelta (Linnaeus) (Lepidoptera :
References
Tortricidae) from Queensland. Journal of the Australian
Entomological Society 8: 79-86.
Anonymous (1974) Recommended methods for the detection
and measurement of resistance of agricultural pests to Varela, L & Welter, S.C (1990) Codling moth resistance in pear
orchards in California. In: Research Reports: 64tb Annual
pesticides. Tentative method for adults of the codling moth,
Laspeyresia pomonelta (L.) - FAO Method No. 11. FAO Plant
Western Orchard Pest and Disease Management Conference.
Protection Bulletin 22: 108-111.
Portland, Oregon, USA: pp. 40-41.
Conclusion
168