J. Appl. Entomol. 131(5), (2007) doi: /j x

Transcription

1 J. Appl. Entomol. 131(5), (27) doi: /j x Journal compilation Ó 27 Blackwell Verlag, Berlin Dual pheromone dispenser for combined control of codling moth Cydia pomonella L. and oriental fruit moth Grapholita molesta (Busck) (Lep., Tortricidae) in pears A. L. Il ichev 1, D. G. Williams 1 and L. J. Gut 2 1 Primary Industries Research Victoria, Department of Primary Industries, Tatura Centre, Tatura, Vic., Australia; 2 Department of Entomology, Michigan State University, East Lansing, MI, USA Ms. received: July 11, 26; accepted: April 5, 27 Abstract: Codling moth (CM) and oriental fruit moth (OFM) are very important orchard pests worldwide, and particularly in Victoria, Australia, where both species damage pome fruit. Individually CM and OFM have been controlled successfully by pheromone-mediated mating disruption, but treatment of pome fruit with full registered rates of two individual hand-applied dispensers for CM and OFM could be uneconomical for growers. Field trials conducted over three seasons in plots sprayed with insecticides consistently demonstrated that dual Isomate C/OFM TT dispensers, designed to disrupt both CM and OFM, were as effective as Isomate CTT and Isomate OFM Rosso dispensers applied individually in pears for control of CM and OFM respectively. The dual- and individual-species dispensers reduced moth catches and fruit damage to a similar degree. The results suggest that combined control of CM and OFM in pears by applying dual Isomate C/OFM TT dispensers at the full-recommended rate of 5 dispensers per hectare will be more economical than use of individual species dispensers, because the price and application cost of dual dispenser is about half that for individual dispensers. Key words: codling moth, mating disruption, oriental fruit moth, pome fruit, sex pheromone 1 Introduction Oriental fruit moth (OFM) Grapholita molesta (Busck) and codling moth (CM) Cydia pomonella L. (Lep., Tortricidae) are the major direct pests of Australian stone and pome fruits. Historically Australian fruit growers were advised that OFM is the primary pest of stone fruit and mostly damages peaches and nectarines (Rothschild and Vickers 1991), while CM mostly damage pome fruit such as apples and pears (Geier 1963). However, in recent years OFM has become a serious problem in Australian pome fruit as well, especially pears in Victoria (Il ichev et al. 1998), possibly due to increased planting of stone fruit near pome fruit and changes in management practices. In the USA and Canada, OFM is a well-known pest of apples (Chapman and Lienk 1971), with recent increases in severe damage (Kovanci et al. 24). These pests have the ability to migrate and infest new host plants and Australian growers now need to address both OFM and CM control in pome fruit pest management programmes. Pheromone-mediated mating disruption is widely used in Australia as a major part of the integrated pest management (IPM) programmes in orchards (Williams and Il ichev 23). In Australian stone fruit, OFM has been successfully controlled through the use of mating disruption (MD) for more than 15 years (Vickers 199; Sexton and Il ichev 2). Successful control of CM in pome fruit also has been achieved with the use of MD alone or in conjunction with limited insecticide treatments (Vickers et al. 1998). Area-wide MD treatments (11 ha) during two consecutive seasons ( ) in Victorian orchards led to a significant reduction in both the OFM population level and damage to stone fruit in the MD-treated area (Il ichev et al. 22). The area-wide MD programme also controlled OFM outbreaks and reduced border damage attributed to migration of OFM. These significant reductions in shoot and stone fruit damage indicated that OFM can be successfully controlled by MD and support the areawide approach to MD applications (Il ichev et al. 22). Successful and long-term control of CM with areawide MD treatment of pome fruit was demonstrated in the western USA during 5 years of a governmentsupported programme (Brunner et al. 21). Incorporation of selective area-wide MD treatments of major pests into IPM programmes has potential for development of cost effective strategies for controlling pests, while improving protection of the environment by

2 Dual pheromone dispenser for CM and OFM 369 reducing the amount of pesticides applied in orchards (Williams and Il ichev 23). Unfortunately, when Victorian fruit growers applied MD on pome fruit for control of CM only, infestation by OFM on pome fruit increased in some orchards (Il ichev et al. 23, 24). The separate application of MD dispensers at the registered rate for both OFM and CM as a solution for managing the two pests in pears is expensive and laborious. Il ichev and Sexton (22) demonstrated that if the initial OFM density in pears neighbouring MD-treated peaches was low, growers could reduce the cost of MD by applying half of the registered rate of Isomate OFM Rosso to the pears. This treatment reduced the number of OFM caught in all experimental pear blocks, and gave similar results as MD with the full registered rate of Isomate OFM Rosso. There were no trials done for CM and OFM combined control in Australian pear orchards and the labour cost issue was not fully addressed. Although fruit growers were enthusiastic about the possibility of combined area-wide MD treatment for CM and OFM control, the high costs of labour and materials associated with application of the two individual dispenser types restricted it s adoption (Brown and Il ichev 2). To address this, a dual dispenser containing the full-recommended dose of CM pheromone and 28% of the OFM pheromone dose combined in one dispenser was developed. This study was designed to assess the effectiveness of the dual hand-applied dispenser, Isomate C/OFM TT for MD of both CM and OFM in comparison with Isomate CTT and Isomate OFM Rosso applied individually for control of the two key internal feeding pests of pome fruit. 2 Materials and Methods 2.1 Dispensers for OFM and CM mating disruption The Isomate OFM Rosso (Shin-Etsu Chemical Co. Ltd, Chiyoda-ku, Tokyo, Japan) used in Australia for MD of OFM is a controlled release formulation of polyethylene dispenser with tube of 1.2 mm in diameter and.9 mm wall thickness. Each dispenser is filled with a three-component blend of OFM sex pheromone: (Z)-8-dodecenyl acetate (223 mg/dispenser), (E)-8-dodecenyl acetate (14.5 mg/dispenser) and (Z)-8-dodecenol (2.5 mg/dispenser). The polyethylene used in Isomate OFM Rosso contains a red pigment to protect the active ingredient from degradation in sunlight. The average loading is about 24 mg of active ingredient per dispenser. The registered application rate in Australia for Isomate OFM Rosso is 5 dispensers per hectare in peaches and nectarines. The Isomate CTT dispenser (Shin-Etsu Chemical Co. Ltd) used for MD of CM has a double tube capillary loaded with a three-component blend of CM sex pheromone: (E,E)- 8,1-dodecadienol (215 mg/dispenser), dodecanol (12 mg/ dispenser) and tetradecanol (27.5 mg/dispenser). The polyethylene used in Isomate CTT also contains a red pigment to protect the active ingredient from degradation in sunlight. The average loading is about mg of active ingredient per dispenser. The registered application rate in Australia for Isomate CTT is 5 dispensers per hectare in apples and pears. Late in 21, a dual tube dispenser containing the sex pheromones of both OFM and CM became available in Victoria, Australia for field trials. The Isomate C/OFM TT dispenser is very similar by design to Isomate CTT dispenser. It is a double tube capillary with the same internal diameter and red pigmentation for protection in sunlight as Isomate CTT. Isomate C/OFM TT contains the same loading of CM sex pheromone as Isomate CTT and is designed to last for about 18 days through the growing season for late varieties. However, it only contains 28% of the loading of OFM sex pheromone found in Isomate OFM Rosso and is designed to last during the first two flights of OFM in spring. The specific loading rate of Isomate C/OFM TT is as follows: (E,E)-8,1- dodecadienol (215 mg/dispenser), dodecanol (12 mg/dispenser) and tetradecanol (27.5 mg/dispenser) and OFM sex pheromone consisting of (Z)-8-dodecenyl acetate (62.44 mg/ dispenser), (E)-8-dodecenyl acetate (4.6 mg/dispenser) and (Z)-8-dodecenol (.7 mg/dispenser). The ratio of the OFM pheromone components in Isomate C/OFM TT (92.17:6.8:1.3) is similar to the ratio in Isomate OFM Rosso (92.9:6.5:1.5). 2.2 Experimental sites, treatments and design A field trial was established in 21 in Victoria, Australia in a large commercial pome and stone fruit orchard with a history of OFM and CM infestation. Three uniform blocks of pears, each 6 ha in size, were selected as trial blocks. The trial was laid out in a randomized complete block design (RCBD) using these three blocks as three replications. The treatments consisted of (1) the full-recommended rate of dual Isomate C/OFM TT dispensers (C/OFM), (2) the full registered rates of Isomate CTT and Isomate OFM Rosso (2CTT+2Rosso) dispensers, and (3) a control without any MD treatment. Each block was divided into three 2-ha plots to test these three treatments. All plots were square in shape. Sampling was conducted in the middle of each plot to minimize the effect of inter-plot treatment interference. The trial was repeated on the same experimental plots for three consecutive seasons from 21 to 24. The first replicate was established in Packham s Triumph (PKT) pears surrounded by Taylor Queen peaches to the north, Cripps Pink apples to the south, Cripps Red apples and PKT pears to the east and T-212 peaches and PKT pears to the west. Two other replicates were established in pears [PKT and Williams Bon Chretien (WBC) varieties combined]. One replicate was surrounded by PKT pears to the south, water channel to the west, WBC pears to the north and PKT pears to the east. The other replicate was surrounded by pasture to the north and west, and PKT pears to the east and south. The experiment was conducted on a single orchard to ensure that management practices, including spraying, were consistent across all treatments, plots and replicates. Most commercial pear blocks in Victoria if not treated with MD were treated with parathion-methyl and/or azinphos-methyl applied about seven to 14 times for control of both CM and OFM. As all of the experimental plots were within an areawide MD treatment area, the grower was uncomfortable leaving control blocks totally untreated. The ability to assess efficacy of MD treatments would have been compromised if chemical sprays were applied only to the control area without MD. Therefore, the experiment was designed so that all plots in the entire experimental area were sprayed with the same chemical at the same time. This allowed us to compare the three treatments under uniform non-treatment conditions. All MD treatments with dispensers of Isomate C/OFM TT, Isomate CTT and Isomate OFM Rosso were applied in the

3 37 A. L. Il ichev, D. G. Williams and L. J. Gut experimental blocks by the middle of September (early spring) of each growing season. The treatments were assessed by comparison of the pest population levels and fruit damage over a period of three growing seasons. 2.3 Monitoring of OFM population Adult populations of OFM in pear blocks were monitored weekly with food and sex pheromone traps. Efecto-fly traps (Avond Pty. Ltd, Narrogin, Australia) were used as food and sex pheromone traps to monitor the population of pests. In all plots, pheromone and food traps were placed at a height of m in the tree canopy. Three food traps were placed in a line through the middle of each experimental plot. Food traps placed in a tree row were spaced by approximately 36 m (five pear trees between food traps). Each food trap consisted of approximately 1 L of 1 g/l dark brown sugar solution with 12 drops of terpinyl acetate solution (48.5 ml of terpinyl acetate with 1.5 ml of non-ionic wetting agent and 5 ml of warm water). One sex pheromone trap for OFM monitoring was placed within each treatment plot. Each sex pheromone trap was placed at a distance of approximately 54 m away from the nearest food trap to minimize interference between traps. High-dosage sex pheromone lures were not available for OFM monitoring in Australia, therefore red rubber septa with 1 mg of OFM sex pheromone (Tréce Ltd., Salinas, CA, USA) were replaced in traps every 6 weeks. The sugar and terpinyl acetate solutions were changed weekly after the trapped moths had been identified and removed. The sex pheromone traps were also monitored weekly for OFM numbers. The monitoring of OFM normally began at the end of August or beginning of September before the first OFM flight had started in spring. The monitoring usually finished in the middle of April, 2 weeks after the last flight of OFM had ended to confirm that the OFM flight activity completely finished for the season. 2.4 Monitoring of CM population Pherocon Delta VI traps with sticky inserts baited with highdosage pheromone lures (CM Mega Lure, Tre ce Ltd), were used for CM monitoring under mating disruption. Pheromone traps were placed on poles and suspended as high as possible within the tree canopy. One Pherocon Delta VI trap was placed within each treatment plot in a location that was approximately 72 m away from the nearest sex pheromone trap for CM to minimize interference. Pheromone traps were inspected weekly to count and remove captured moths. Pheromone lures were replaced every 6 weeks. In northern Victoria, CM normally begin to fly about a month later than OFM and CM monitoring usually started at the middle of September before the first CM flight had started in spring. Monitoring usually finished in the middle of April, two weeks after the last flight of CM had ended. 2.5 Damage assessments Pear fruit were inspected at harvest for OFM and CM larval infestation to assess the effectiveness of treatments in preventing damage. OFM damage to pear fruit, but not shoot tips, was assessed because larval feeding in shoot tips in pear is extremely difficult to detect. Damage to pear fruit was assessed about 1 week prior to harvest with a sample of 1 randomly selected fruit per tree from each of the trees in which food traps were deployed. Another 1 fruit from each of three fruit bins per plot were sampled during harvest. It is difficult to distinguish between CM and OFM damage from external examination of pome fruit. Therefore all damaged fruit were cut open for identification of OFM and CM larvae by determining presence (for OFM larvae) or absence (for CM larvae) of the anal comb. The number of fruit damaged by each species was recorded and used for analyses. 2.6 Measurements of pheromone release rates from dispensers The pheromone release rates of Isomate C/OFM TT, Isomate CTT and Isomate OFM Rosso dispensers were determined gravimetrically. Ten dispensers of each type were individually suspended on a wire rack within partial shade in a tree canopy at DPI Tatura near the trial sites, and weighed individually at weekly intervals between 19 September 23 and 3 April 24. The dispensers were brushed to remove dust and weighed to an accuracy of ±.1 mg. The release rates were estimated with the slope of a trend line of the absolute weights of dispensers by calculating the difference in individual dispenser weights at each successive measurement. Meteorological information from the Tatura weather station with maximum and minimum temperature, wind speed and direction was used to prepare figures. In order to determine the release characteristics of individual components of sex pheromone for CM and OFM within the Isomate C/OFM TT dispenser, it was necessary to measure the residual content of the dispensers over time using gas chromatographic analysis. Samples of five exposed dispensers were removed at monthly intervals throughout the season, sealed in foil bags and sent to Shin- Etsu Chemical Company for analysis. The residual quantity of individual components of sex pheromone in the sampled dispensers was determined by solvent extraction with hexane and gas chromatography (GC). The weight loss results were combined with the results of the GC analysis by multiplying the proportion of OFM pheromone determined on each GC analysis point by the incremental weight loss. Where residual analysis points did not coincide with the weight loss data points, an interpolated value between the residual pheromone points was used to approximate the proportion of OFM pheromone remaining at that time. A similar calculation was performed for the proportion of CM sex pheromone determined by GC analysis. 2.7 Statistical analysis To compare the performance of the three treatments, the end-of-season data on total number of OFM and CM catches in each plot were analysed using a randomized complete block design-based repeated-measures analysis of variance (RepMeasanova) in GenStat 8 (Lawes Agricultural Trust, Rothamsted Experimental Station). Use of Rep- Measanova allowed testing for the differences among treatments as well as their interaction with time after duly accounting for any dependence among plot observations over the three seasons. The original data x was transformed to the log e (x + 1) scale for analysis as this more reasonably satisfied the anova assumptions of homogeneity of error variance and normal distribution of errors as revealed by the GenStat-generated diagnostic plots. The significance of the difference between the mean total catch of any two treatments was tested using the Fisher s unprotected least significant difference (LSD) test at 5% level of significance.

4 Dual pheromone dispenser for CM and OFM 371 (a) field season C/OFM 2 CTT+2 Rosso Control OFM / Trap / Week September October November December January February March April (b) field season OFM / Trap / Week September October November December January February March April (c) field season Fig. 1. Catches of OFM in food bait traps pooled from three replications (average of nine traps) under MD treatments with Isomate C/OFM (C/OFM), full registered rates of Isomate OFM Rosso and Isomate CTT (2 CTT+2 Rosso), and no MD (control) on pears (21 24). OFM / Trap / Week September October November December January February March April 3 Results 3.1 OFM catches in food traps The trend of OFM weekly moth catches in food traps during the 21 22, and seasons are shown in fig. 1a c. During 21 22, the highest weekly mean catches of OFM recorded in the peak of the first flight were 25, 6 and 26 OFM/trap in the C/OFM, 2CTT+2Rosso and the control treatments, respectively. At the end of the season, catches of OFM under the 2CTT+2Rosso treatment had slightly increased, but under C/OFM treatment catches decreased to about 5% of those at the beginning of the season. The mean total number of OFM caught in food traps under the C/OFM, the 2CTT+2Rosso and the control treatments were 534, 235 and 498, respectively (table 1). During the 22 23, the highest average weekly number of OFM recorded in the peak of the first flight was 4, 8 and 12 under the C/OFM, 2CTT+2Rosso and the control treatments, respectively. Over the entire sampling period for food traps, the mean total OFM catch was 126 for C/OFM, 159 for 2CTT+2Rosso and 24 for control treatment (table 1). During 23 24, the highest weekly average number of OFM recorded in the highest peak was 9, 12 and 17 OFM/trap in the C/OFM, the 2CTT+2Rosso and control treatments respectively. The mean total OFM catches over the season were 133 for C/OFM treatment, 162 for 2CTT+2Rosso treatment and 23 for control treatment (table 1). The RepMeasanova results based on end-of-season OFM catches in food traps showed a non-significant treatment-by-year interaction (P ¼.174) (table 1)

5 372 A. L. Il ichev, D. G. Williams and L. J. Gut Table 1. Average total number of moths under three treatments during Treatment log e bt log e bt log e bt log e bt Oriental fruit moth in food traps 2CTT+2Rosso C/OFM Control Mean (Year) F Prob(Treat.) ¼.62; F Prob(Year) ¼.2; F Prob(Treat. Year) ¼.174 SED(Treat.) ¼.133; SED(Year) ¼.167; SED(Treat. Year) ¼.289 Oriental fruit moth in sex pheromone traps 2CTT+2Rosso C/OFM Control Mean (Year) F Prob(Treat.) ¼.6; F Prob(Year) <.1; F Prob(Treat. Year) ¼.287 SED(Treat.) ¼.44; SED(Year) ¼.333; SED(Treat. Year) ¼.621 Codling moth in sex pheromone traps 2CTT+2Rosso C/OFM Control Mean (Year) F Prob(Treat.) ¼.16; F Prob(Year) ¼.338; F Prob (Treat. Year) ¼.66 SED(Treat.) ¼.84; SED(Year) ¼.361; SED(Treat. Year) ¼.925 The F probability and the SED apply to log e mean values; bt: back-transformed mean values. implying that the three treatments relatively performed more or less in a similar manner in the three years. The three treatments, averaged across three years, also did not show significant differences in OFM catches (P ¼.62). As expected, the catches however differed significantly from one year to the other (P ¼.2). The general trend was a significant drop in the catches in the second year under each treatment, with a slight increase in the third year. 3.2 OFM catches in sex pheromone traps The mean total number of OFM caught in sex pheromone traps under the C/OFM, the 2CTT+2Rosso and the control treatments were 27, 8 and 193 (during 21 22); 1, 2 and 115 (during 22 23); 2, 1 and 1 (during 23 24) respectively (table 1). There was an obvious decline of the mean total OFM numbers from 27 to 2 caught in sex pheromone traps throughout three consecutive seasons under C/OFM treatment. As in the case of food traps, the RepMeasanova results showed that the three treatments showed a nonsignificant interaction with the years (P ¼.287) implying a nearly consistent trend in OFM catches for the three treatments across the 3 years (table 1). However, in contrast to food traps, catches of OFM in sex pheromone traps for the three treatments, averaged across three years, differed significantly (P ¼.6) with both the non-control treatments showing significantly smaller catches than the control treatment. The year-to-year differences in catches in sex pheromone traps, similar to that in food traps, were also significantly different (P <.1). Overall, the catches in sex pheromone traps were consistently much less than in the food traps. 3.3 CM catches in sex pheromone traps There were no CM captured in two of the three replicates under all treatments during the first two seasons (21 23). However, in the third season (23 24) in these two replicates, 2 and 28 CM males were caught only in the control treatments, indicating the beginning of CM infestation in blocks without MD treatment. CM males were captured in the third replicate under all treatments in the first season (21 22), when mean total CM catches in sex pheromone traps under the C/OFM, the 2CTT+2Rosso and the control treatments were 1, 1 and 2, respectively. There were no CM caught in any of MD treated plots throughout and 23 24, although there was a dramatic increase in mean total numbers of CM caught under control (no MD) treatment from 2 to 22 throughout three consecutive seasons (table 1). The RepMeasanova results (table 1) showed that the treatments did not significantly interact with years (P ¼.66) indicating a nearly consistent relative behaviour of the three treatment across years. The catches under the control treatment in all 3 years were higher than in the non-control treatments. The three treatments, averaged across years, also showed no significant differences (P ¼.16). There were no significant differences among years also (P ¼.338). 3.4 Fruit damage assessments There was no fruit damage detected in the MD-treated plots during the pre-harvest sampling in 22, while in the control (no MD) plots mean fruit damage ranged from.2 ±.14% to.9 ±.29%. Bin damage assessments conducted during harvest in early February 22 confirmed the results of the pre-harvest

6 Dual pheromone dispenser for CM and OFM 373 sample from trees. No CM damage was found in bins harvested from MD plots, but mean OFM damage ranged from.1 ±.1% to.2 ±.14%. Mean OFM damage found in bins from control plots ranged between.3 ±.17% and.8 ±.27%. Pre-harvest sampling in 23 did not detect any damaged pears in the MD treated plots, but damage in the control plots averaged.2 ±.14%. Subsequent assessments of fruit damage in bins during harvest were consistent with pre-harvest assessment from trees. Levels of.1 ±.1% and.2 ±.14% OFM damage were detected in bins harvested from control plots while no fruit damage was recorded in any MD-treated plots. There were no damaged pears detected in any treatments during the pre-harvest sampling. However, bin counts during harvest uncovered an average of.2 ±.14% OFM damage in the control plots. There were no damaged fruit detected in the MD-treated plots. 3.5 Pheromone release rates from Isomate OFM Rosso, Isomate CTT and Isomate C/OFM TT dispensers The release rate characteristics of Isomate C/OFM TT, Isomate OFM Rosso and Isomate CTT dispensers, derived from the weight loss data measured in Tatura from 19 September 23 to 3 April 24 are presented in fig. 2. The release rates of Isomate OFM Rosso and Isomate CTT started close to the OFM mating disruption threshold (Rothschild 1975) and slightly below the threshold for CM disruption (Vickers and Rothschild 1991; Vickers et al. 1998), respectively. The release rates calculated from the residual pheromone (fig. 3) indicated that release of the CM pheromone component of Isomate C/OFM TT started slightly below the threshold range until the end of October 23, but then increased dramatically. The increase in the release rate of all dispensers that began in early November corresponded to an increase in maximum daily temperatures. The release rate from all three dispensers demonstrated similar trends before the 2 C/OFM TT@5/ha 5/ha 5/ha 15 Fig. 2. Release rates of Isomate OFM Rosso, CTT and C/OFM TT calculated from weight loss measurements in Tatura, Victoria (23 24). Threshold for disruption of CM approximately 372 (144 6) mg/ha/day; threshold for disruption of OFM mg/ha/day. mg / hectare / day /9/3 26/9/3 3/1/3 1/1/3 17/1/3 24/1/3 3/1/3 7/11/3 14/11/3 21/11/3 28/11/3 5/12/3 11/12/3 19/12/3 24/12/3 31/12/3 9/1/4 16/1/4 23/1/4 3/1/4 6/2/4 13/2/4 2/2/4 27/2/4 5/3/4 12/3/4 18/3/4 25/3/4 2/4/4 8/4/4 16/4/4 23/4/4 3/4/ CM 4 Fig. 3. Release characteristics of individual components for CM and OFM sex pheromone emitted from dispenser of Isomate C/OFM TT, calculated from results of residual analysis (23 24). Threshold for disruption of CM approximately 372 (144 6) mg/ ha/day; threshold for disruption of OFM mg/ha/day. mg / hectare /day /9/3 3/1/3 17/1/3 3/1/3 OFM 14/11/3 28/11/3 11/12/3 24/12/3 9/1/4 23/1/4 6/2/4 2/2/4 5/3/4 Max. Temperature 18/3/4 2/4/4 16/4/ Maximum daily temperatures c

7 374 A. L. Il ichev, D. G. Williams and L. J. Gut middle of December (fig. 2), but the magnitude was different reflecting the different loadings of active ingredients in the different dispensers. The release rate of Isomate C/OFM TT dispenser declined after 24 December 23, probably because the OFM pheromone loading had been released completely (fig. 3). The release from Isomate OFM Rosso and Isomate CTT showed similar patterns of decline in release rates over this period, however Isomate CTT maintained higher release rates for a longer period (fig. 2). The release rate of Isomate OFM Rosso was low, but above the threshold for effective mating disruption of OFM until 16 April 24 (fig. 2). The release characteristics of individual components emitted from the Isomate C/OFM TT dispenser, calculated from the results of gas chromatography analysis of residual individual components of CM and OFM sex pheromone in the sampled dispensers are presented in fig. 3. The initial emission rate of the OFM sex pheromone components from Isomate C/ OFM TT was 6 mg/ha/day, well above the threshold for OFM disruption. There was a substantial decrease in the release of OFM pheromone on 17 October 23, but rate gradually increased over the next 4 weeks, returning to the starting level of 6 mg/ha/day on 7 November 23. Subsequently, the emission of OFM pheromone steadily declined and fell below the threshold for mating disruption of this species on 31 December, approximately 1 days after exposure. Very low levels of OFM pheromone were emitted after this date. The emission rate of the CM sex pheromone components from Isomate C/OFM TT initially was below the threshold for CM disruption, but increased steadily, and exceeded the threshold on 24 October 23 (fig. 3). The emission rate increased sharply after this date, peaking on 19 December 23, and remained above the threshold level until 12 March 24. However, a small amount of CM sex pheromone continued to be released for more than 2 days in the field. 4 Discussion The use of dual dispensers of Isomate C/OFM TT provided equivalent levels of fruit protection, over three consecutive fruit growing seasons, to that achieved from application of individual dispensers of Isomate CTT and Isomate OFM Rosso together. The experiment was designed to compare the efficacy of the two approaches to MD in orchards where both CM and OFM were present. The only orchards available with sufficiently large and uniform blocks that could accommodate the experimental design were commercial orchards. The risk of fruit damage to the large ÔuntreatedÕ control blocks in commercial orchards necessitated the experimental design wherein the control blocks were treated with insecticides. By spraying all treatments, including the control, with the same spray regime we were able to compare the relative effectiveness of the pheromone treatments and to assess the benefits of applying insecticides to supplement MD. Trimble et al. (21, 24) recommended the use of insecticide sprays against the first generation and then MD for subsequent generations of OFM. However, OFM emerging in spring in pears not treated with MD posed a risk to neighbouring peach crops treated with MD since moths mated in the pear block moved into the peaches to lay eggs (Il ichev et al. 22, 23). To account for this, Australian recommendations are to use MD against the first and subsequent generations. Neither MD treatment sustained detectable fruit damage during the three seasons of the experiment, whereas only the insecticide-treated controls had damage each season. The treatment with Isomate C/OFM TT reduced OFM catches in food traps by 75.28% from to 23 24, whereas treatments with Isomate CTT and Isomate OFM Rosso and the control reduced catches by 3.88% and 53.75%, respectively, over the same period. The fact that moths were still caught by food traps in the pheromone treatments indicates that the treatments do not completely disrupt all matings, and reinforces the belief that sex pheromone traps are not a reliable indication of moth populations in MD-treated orchards. The dual dispensers of Isomate C/OFM TT utilise the polymer from the Isomate CTT dispenser rather than that in the Isomate OFM Rosso dispenser. The release rate of OFM pheromone components from this dispenser is greater than from the Isomate OFM Rosso dispenser (S.B. Sexton pers. comm.) and this was supported by comparison of the gas chromatography analysis (fig. 3) and the weight loss results for Isomate OFM Rosso (fig. 2). The two methods for computing release rate gave comparable results for total release rate from Isomate C/OFM dispensers. Assuming this is reflected in the release rates of the components, the Isomate C/OFM TT dispenser released more OFM pheromone that did Isomate OFM Rosso dispenser during September and October, but thereafter the release rate was lower and was below the threshold for effective MD of OFM by the end of December. The early-season release rate of OFM pheromone components appears to have reduced the OFM population to levels low enough for control by insecticide alone from December to the rest of the season. Evenden and McClaughlin (25) demonstrated increased attractiveness to OFM males, but decreased attractiveness to CM males, of a combined sex pheromone-based attracticide formulation designed for both CM and OFM. Their study suggested interference between sex pheromone formulations designed for these two species as was demonstrated before for other tortricid species (Judd and Gardiner 24). In our trials the MD treatments controlled a low population of CM throughout the experiment, but CM populations increased in the insecticide-treated controls. This suggests that there is no negative impact on CM disruption by interaction between the CM and OFM pheromone components in the same dispenser. However, it is important to note that the OFM components in the Isomate C/OFM TT formulation would have mostly been released by the start of the

8 Dual pheromone dispenser for CM and OFM 375 second CM flight in January and hence the Isomate C/OFM TT and Isomate CTT dispensers would then be expected to perform identically with respect to CM mating disruption. The increase in OFM numbers in February March of the first two seasons is most likely due to cessation of pesticide usage in the pears during January before harvest. The presence of undersized or poor quality fruit, left on the trees after commercial harvest, could have provided a suitable food resource to complete another generation. Previous studies have indicated that three consecutive seasons of MD treatments are required to reduce OFM populations to numbers low enough for damage levels acceptable to commercial growers (Il ichev et al. 22). The combination of Isomate C/OFM TT treatment supplemented with insecticides holds promise as a way of reducing damage to low levels without the expense of season-long MD for OFM. Growers using Isomate C/OFM TT will need to recognize that the release rate of OFM pheromone does not match that of Isomate OFM Rosso in the latter half of the season. This could present a problem if the initial OFM population is higher than in our study. Further studies are required to determine moth population thresholds that would provide guidance for decision making. Acknowledgements The Department of Primary Industries (DPI), Victoria and Horticulture Australia Ltd funded this research. We thank the following people from DPI, Tatura: Mr Chris Sheehan, Ms Elizabeth Alsop and Mr. Neil Penfold for monitoring and assistance with data preparation for analysis, Dr Alvin Milner and Dr Subhash Chandra for experimental design discussions and for statistical analysis. Also we thank Mr Stephen Sexton (Biocontrol Ltd, Qld, Australia) for supplying the mating disruption dispensers for trials, and chemists from Shin-Etsu Chemical Company (Chiyoda-ku, Tokyo, Japan) who determined the residual quantity of individual components of the sex pheromone in the Isomate C/OFM TT dispensers. We also thank Dr Lukasz Stelinski from the Department of Entomology at Michigan State University, USA for thorough review of the manuscript. References Brown DJ, Il ichev AL, 2. The potential for the removal of organo-phosphate insecticides from stone-fruit production in the Goulburn Valley, Australia. Acta Hort. 525, Brunner J, Welter S, Calkins C, Hilton R, Beers E, Dunley J, Unruh T, Knight A, VanSteenwyk R, VanBuskirk P, 21. Mating disruption of codling moth: a perspective from the Western United States. 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9 376 A. L. Il ichev, D. G. Williams and L. J. Gut tortricid pests: their biology, natural enemies and control, Vol. 5. Ed. by Van der Geest LPS, Evenhuis HH, Elsevier, Amsterdam, Vickers RA, Thwaite WG, Williams DG, Nicholas AH, Control of codling moth in small plots by mating disruption: alone and with limited insecticide. Entomol. Exp. Appl. 86, Williams DG, Il ichev AL, 23. Integrated pest management in Australia, Chap. 28. In: Integrated pest management in the global arena. Ed. by Maredia KM, Dakouo D, Mota-Sanchez D, CABI Publishing, Oxon, Author s address: Dr Alex Il ichev (corresponding author), Department of Primary Industry, Primary Industries Research Victoria, Tatura Centre, Ferguson Road, Tatura, Victoria 3616, Australia. alex.ilichev@dpi.vic.gov.au