SELECTIVE PESTICIDES AND BIOLOGICAL CONTROL IN WALNUT PEST MANAGEMENT

Transcription

1 SELECTIVE PESTICIDES AND BIOLOGICAL CONTROL IN WALNUT PEST MANAGEMENT N.J. Mills, K. Mace-Hill, R.A. Van Steenwyk, C. Pickel, and J. Grant ABSTRACT In recent years we have also seen dramatic changes in the pest management tools in walnuts driven by Food Quality Protection Act -mandated reductions in organophosphate (OP) use, and the increasing costs of replacement pesticides. Codling moth as the key pest of walnuts has traditionally been controlled by multiple sprays of OPs applied per season. While the development of new approaches to the use of pheromone-based mating disruption shows promise as an alternative to reliance on insecticides, new reduced risk insecticides are replacing the OPs. Disruption of the biological control of secondary pests by natural enemies through use of these new reduced risk products can lead to reliance on pesticides for suppression of secondary pests such as the walnut aphid Chromaphis juglandicola. The goal of this project is to screen new pesticides to identify selective products that will enhance the level of biological control of walnut aphid in orchards as part of a larger western regional USDA-SCRI project ( From bioassays of currently registered and new pesticides in walnuts, it appears that applications of OPs and pyrethroids kill the parasitoid T. pallidus more effectively than they kill walnut aphids and so have the potential to be disruptive of biological control. Surprisingly, products such as Delegate, Success and Omite also show the same potential effects. The IGRs tested seem to be compatible with biological control, and Altacor selectively kills aphids and hyperparasitoids without impacting T. pallidus. This suggests that Altacor could selectively enhance the impact of biological control, although another diamide Cyazypyr shows greater toxicity to a broad range of natural enemies. Sublethal bioassays suggested that Warrior II also causes a strong reduction in daily fecundity of adult wasps that survive. Despite an unusually cool summer season in 00, a replicated field study of the comparative impacts of Altacor and Delegate in a walnut orchard confirmed that Delegate applied for nd generation codling both caused a severe reduction in parasitism of walnut aphid and elevated aphid densities in August. Results from the USDA-SCRI project suggest similar acute and sublethal toxicities for other orchard natural enemies, and suggest that plant-based volatiles identified so far can effectively be used to monitor the activity of a range of key natural enemies in orchards, such as parasitoids, syrphids and green lacewings. INTRODUCTION In recent years we have also seen dramatic changes in the pest management tools in walnuts driven in part by Food Quality Protection Act -mandated reductions in organophosphate (OP) use, and in part due to water quality issues. Codling moth as the key pest of walnuts has traditionally been controlled by multiple sprays of OPs applied per season. While the development of new approaches to the use of pheromone-based mating disruption shows promise California Walnut Board 79 Walnut Research Reports 00

2 as an alternative to reliance on insecticides, new reduced risk insecticides are replacing the OPs. The latter are likely to remain an important tool in the management of codling moth, but their impacts on natural enemies are poorly understood and often much greater than might be expected. Information developed by participants in a western regional USDA-SCRI grant suggests that we may be creating unstable management programs because of the negative effects of some of the newer pesticides on natural enemy populations. Disruption of the biological control of secondary pests by natural enemies through use of these new reduced risk products can lead to a reliance on pesticides for suppression of secondary pests that is costly both economically and ecologically, and is detrimental to worker safety. To remain competitive, stable IPM programs that effectively conserve natural enemies must be developed as even a small increase in natural enemy induced-mortality significantly lowers potential pest pressure. The walnut aphid, Chromaphis juglandicola (Kaltenbach) has been known in California for more than 00 years. When present in large number in the spring, aphid feeding reduces tree vigor, nut size and quality. During the summer, it induces a shriveling of the kernels before harvest. Extremely high populations of aphids may lead to leaf drop, exposing nuts to sunburn. The introduction of the parasitic wasp Trioxys pallidus (Halliday) from Iran in 969 led to a dramatic success in the biological control of walnut aphid populations in California, and has provided sustained control of this devastating pest for the past 9 years. However, both growers and PCAs have noted that aphid outbreaks, though not consistent, are of increasing concern in the Central Valley with in-season spray treatments required in some cases. As pest management practices in walnuts change to both reduce costs and make use of new pesticides, it is important to retain the benefits of the long-term biological control of walnut aphid provided by the introduction of T. pallidus. The goal of this project is to screen new pesticides to identify selective products that will enhance the level of biological control of walnut aphid in orchards as part of a larger western regional USDA-SCRI project ( Other collaborators in the larger project will be screening a broader range of natural enemy species to build a more comprehensive picture of the selectivity of new reduced risk pesticides that could disrupt the natural enemy control of other pests such as codling moth and spider mites. An additional benefit of participation in the larger regional project is that an additional component of the latter is to develop the use of herbivore-induced host plant volatiles as an effective tool for growers and PCAs to monitor the activity of natural enemies under different pest management practices. esticides that are currently or likely to be registered for use in walnuts in the near future, using both acute and sublethal tests to determine their impact on walnut aphid, T. pallidus and its dominant hyperparasitoid Syrphophagus aphidivorus. The outcomes of these bioassays will then be used to verify impact in replicated field trials in walnut commercial orchards. OBJECTIVES The general objective is to better understand the impact of new pesticides used for the management of primary pests in walnuts on the walnut aphid system, one of the best examples of an effective biological control in western orchards. The specific objectives are: California Walnut Board 80 Walnut Research Reports 00

3 . To assess the differential susceptibility of walnut aphid, T. pallidus, and S. aphidivorus to walnut pest management products using simple laboratory bioassays.. To use a sublethal demographic bioassay to test a subset of pest management products for their compatibility with and enhancement of biological control of walnut aphid.. To verify the impact of pesticides identified as disruptive from the laboratory bioassays through large block replicated field trails in walnut orchards. PROCEDURES Objective. To assess the differential susceptibility of walnut aphid, T. pallidus, and S. aphidivorus to walnut pest management products using simple laboratory bioassays This year laboratory assays were used to determine the potential disruptive effects of pest management products on the survivorship of adult Trioxys pallidus and Syrphophagus aphidivorus exposed orally and to surface residues. Products tested included those currently registered in walnuts either for codling moth, husk fly or aphids including the insecticides Guthion (as a historical baseline), Imidan and Lorsban (OPs), Asana, Brigade and Warrior (pyrethroids), Altacor and Cyazypyr (diamides), Agri-Mek, Delegate and Success (microbial metabolites), Intrepid and Rimon (IGRs), and Omni oil (organic), the acaricide Omite, and the fungicides sulfur (Kumulus) and Kocide-Manzate. A full strength solution (00% field rate) was used to represent the concentration that the wasps would experience at the time of application, a dilute solution (0% or 5% field rate) was used to represent the possible concentration that the wasps would be exposed to after field weathering, and these were both compared to water (0% field rate) as a control. The full field rates of these products are shown in Table. Glass vials (8 x.5 cm) were filled with pesticide solutions and then drained and dried to provide a consistent residue on the inner surface. Similarly, small droplets of a honey-sugar-agar-water mixture ( ratio) were used as food for the adult parasitoids and treated by dipping in insecticide solutions to gain a surface coating of residue. A male and female pair of - day old adult wasps were placed into a treated glass vial, provided with treated food, and held at C and 6h daylength. From 0-0 replicate vials were used for each parasitoid species and each pesticide treatment, and adult survivorship was monitored after 48h. The acute mortality of parasitoid adults in each replicate vial was analyzed separately for the two parasitoid species and survivorship data from the full field rate and dilute rate were corrected for control mortality using Abbott s correction. Following Dorfman et al. (980, Regulating Pesticides, NAS Press), 95% confidence intervals were calculated from a second order approximation of the maximum likelihood variance. California Walnut Board 8 Walnut Research Reports 00

4 Objective. To use a sublethal demographic bioassay to test a subset of pest management products for their compatibility with and enhancement of biological control of walnut aphid For those pesticide products that did not show acute toxicity at the dilute concentration, sublethal bioassays were also carried out for T. pallidus. Unlike traditional pesticides that frequently caused acute toxic impacts on natural enemies, the newer classes of pesticides tend to have greater impacts on life history performance than on survivorship. These effects can often be equally important in reducing the abundance of natural enemies in orchards and are best evaluated using specifically designed sublethal bioassays. A control and a single concentration of each product were compared in the sublethal bioassays, the single concentration corresponding to the greater of the two concentrations used in the acute bioassay that killed less than 70% of the test wasps. As a bioassay arena, glass cylinder of.6cm height by.4 cm diameter were sprayed with.95 ml of test solution in a Potter tower, turned over, and sprayed with.95 ml of solution again, resulting in residue deposit of.5 mg cm -. When dry, these cylinders are used to make clip cages to attach to walnut leaves on a potted seedling plant. For adult food for the wasps 0 ul droplets of 50:50 honey-water solution were pipetted into a plastic-wrap-covered petri dish and sprayed with.05 ml of test solution. Finally, T. pallidus adults less than 4h old were knocked out with 5 seconds of compressed CO at 0 PSI, and then topically sprayed in Potter tower with.05 ml of test solution. Female-male pairs were placed in treated clip cages on walnut seedlings with 5 rd instar yellow walnut aphids and two streaks of treated honey solution. After 4h, the experimental females were transferred to another treated clip cage (treated at the same time as the original) containing a fresh set of 5 hosts and honey solution. An untreated, slightly larger-diameter clip cage was then placed around the previous day's hosts and followed to monitor mummy formation and adult parasitoid emergence. The experimental adults were maintained in the sublethal assays for a period of days, representing the first 40% of their typical lifespans. The experimental insects were kept at a 6:8h light:dark photoperiod at C. Adult survivorship and daily fecundity, and progeny development time and sex ratio were noted from these bioassays. Each of these life history parameters for the experimental wasps was compared to those of the control wasps using ANOVA with an arcsine square root transformation for percentage data, and log transformation for count data. As it is not intuitively obvious whether an increase of development time would be more detrimental than a similar magnitude of decrease in daily adult fecundity, the life history parameters were integrated into a single population-level index of impact using a demographic model. Stage structured matrix models provide a simple approach to translating individual-level responses to pesticide exposure to likely effects on populations of natural enemies in the field. The model for T. pallidus was constructed with three life stages, juvenile, mummy, and adult and parameterized based on data collected from untreated adults held in clip cages on potted walnut seedlings. The impact of each pesticide on T. pallidus was then estimated by changing those life history parameters in the model that were significantly impacted in the sublethal assays. California Walnut Board 8 Walnut Research Reports 00

5 Objective. To verify the impact of pesticides identified as disruptive from the laboratory bioassays through large block replicated field trails in walnut orchards To verify the observations from the acute and sublethal bioassays in the lab, a replicated field trial was carried out in 00. For these trials we compared two products that appear to differ in their general effects on natural enemies from the lab bioassays Delegate that appears to be disruptive, and Altacor that appears to be compatible. The trial was carried out in a walnut orchard near Chico. The field applications were timed for codling moth management and applied once during each of the first two generations. Five treatments were used in the trial, Altacor or Delegate only, Altacor followed by Delegate or vice versa, and a no applications control. While a typical set of blight applications and mating disruption for codling moth were used in the orchard, no other pesticides were applied through the season. Plot size was approximately 0.8 acres consisting of 5 rows of 8 trees and each treatment was randomized in a set of four replicate blocks. Aphids and spider mites and their associated natural enemies were sampled at two week intervals throughout the season by collecting three compound leaves from each of five trees in the three center rows of each plot. The abundance of aphids and their natural enemies was counted directly from each leaflet, while the abundance of spider mites and predatory mites were determined after removal from the foliage with a mite-brushing machine. As the number of leaflets on the compound leaves varied through the season, the count data were first standardized to number per leaflet before being analyzed. The cumulative season-long totals of aphid, mite and natural enemy abundance were analyzed using ANOVA, and the seasonal patterns were examined analyzed using ANOVA at each sample date. RESULTS Objective. To assess the differential susceptibility of walnut aphid, T. pallidus, and S. aphidivorus to walnut pest management products using simple laboratory bioassays By testing the differential susceptibility of walnut aphid, its primary parasitoid T. pallidus and its hyperparasitoid S. aphidivorus we are beginning to build a better picture of the selectivity of the different pesticides that are used for management of codling moth, walnut husk fly and walnut blight in the context of the biological control of walnut aphid. The acute toxicity (48h mortality) of the key insects, representing the three successive trophic levels, to the various products is presented in Fig.. At a standard field rate the two traditional OP insecticides, Guthion and Lorsban, killed 00% of the rd instar nymphs of the walnut aphid, adults of T. pallidus and adults of S. aphidivorus (Guthion not yet tested for the hyperparasitoid). The two pyrethroids, Asana and Warrior II, had a similar acute impact at all three trophic levels. The two diamides, Altacor and Cyazapyr, showed higher acute toxicity to the walnut aphid than expected, and while Cyazypyr was acutely toxic to T. pallidus Altacor was not, although it showed relatively high acute toxicity to S. aphidivorus. The two spinosyns, Delegate and Success, proved to be acutely toxic to both T. pallidus and S. aphidivorus, and showed a similar level of toxicity to the walnut aphid as the two diamides. The two IGRs, Intrepid and Rimon, had no acute effect on walnut aphid, T. pallidus or S. aphidivorus, as might be expected for a more selective class of insecticides. In contrast, California Walnut Board 8 Walnut Research Reports 00

6 contrary to expectations, both Omni oil and the acaricide Omite were acutely toxic to T. pallidus (tests for S. aphidivorus not yet completed) and killed approximately 90% and 70% of the aphids respectively. Then finally, Kocide-Manzate that is used repeatedly for control of walnut blight had no acute impact on either the aphids or T. pallidus, as might be expected. Thus these acute bioassays suggest two important findings. Firstly, that use of Omite for spider mite management could be disruptive to biological control of walnut aphid as it selectively kills T. pallidus rather than aphids. Secondly, that use of Altacor as a codling moth treatment may enhance the biological control of walnut aphid by selectively killing aphids and hyperparasitoids rather than T. pallidus. Objective. Objective. To use a sublethal demographic bioassay to test a subset of pest management products for their compatibility with and enhancement of biological control of walnut aphid The second tier demographic bioassays were used for those pesticides that proved not to be acutely toxic to T. pallidus in the first tier bioassays (Fig. ) to test for potential sublethal effects that could influence the life history performance of the wasps. Thus sublethal assays were conducted on T. pallidus only for those pesticides that killed less than 75% of the adult wasps of the acute bioassays. These were Altacor, Rimon and Kocide-Manzate at the standard field rate, and Warrior II and Kumulus at a 0% field rate. Both Kocide-Manzate and Rimon had no significant impacts on the life history performance of T. pallidus in the sublethal assays in comparison to controls (Table ). The fungicide Kumulus had the greatest range of sublethal effects significantly reducing the survivorship of adult T. pallidus by 58% as well a significantly reducing the daily fecundity of adults that did survive by 64%. In contrast, the only significant sublethal effect of Altacor and Warrior II was on the daily fecundity of adult T. pallidus, which was reduced by 5% and 84% respectively. The acute and sublethal effects of these same pesticides on a range of other natural enemies that play an important role in western orchards have been determined by other members of the USDA-SCRI project ( and are presented in Table. The most consistent acute effects were generated by Delegate and Warrior II, while Cyazypyr showed acute effects on spiders (P. aeneola and M. lepidus) and T. pallidus, and Kumulus showed weaker acute effects on Galendromus occidentalis and the two parasitoids. The sublethal effects were generally mediated through either reduced survivorship or daily fecundity. Altacor showed sublethal effects on spiders and T. pallidus, but not G. occidentalis or D. brevis. Similarly, where tested, Kumulus and Kocide/Manzate also showed moderate sublethal effects for some natural enemy species. Thus of the four materials used as codling moth treatments, Delegate appears likely to be most disruptive of natural enemies of secondary pests and Altacor appears to be the most compatible. California Walnut Board 84 Walnut Research Reports 00

7 To better understand how the sublethal effects of a standard field rate of Altacor and Kumulus are likely to compare to the acute and sublethal effects of a dilute rate of Warrior II or the acute toxicity of a standard field rate of Cyazypyr, these individual responses to toxicity were integrated to population impacts using stage-structured matrix models. The outcome of this integration (Fig. ) indicates that a population of T. pallidus has the potential to grow from 00 to 000 individuals within 8 days in the absence of exposure to pesticides (control). The mild sublethal toxicity of Altacor would delay that growth by days to 0 days, whereas the combined acute and sublethal toxicity of a dilute rate of Warrior II would delay the growth by 4 days to 4 days. These models allow the diverse toxic effects that the pesticides have on individuals of T. pallidus in the laboratory bioassays to be integrated and ranked in terms of their likely population impacts on T. pallidus in the field. Objective. To verify the impact of pesticides identified as disruptive from the laboratory bioassays through large block replicated field trails in walnut orchards One of the drawbacks of testing pesticide impacts on natural enemies in the field is that populations of the natural enemies and their hosts can remain low due to environmental influences such as climate. The unusually cool spring and summer in 00 did not support the development of populations of either walnut aphid or spider mites in the walnut orchard near Chico despite a history of aphid activity in previous years. Spider mite and predatory mite populations remained well below per leaflet until September and were too low to be able to detect and impacts of the pesticide treatments applied to the replicated plots, and so will not be considered further. Walnut aphid populations also remained low, but in this case the populations were just large enough to be able to detect significant impacts of the pesticide treatments (Fig. ). Aphid populations built to a peak of around.5 individuals per leaflet in late May, dropped to very low levels late June and built to a late summer peak of individuals per leaflet in mid August. There was no difference in the abundance of walnut aphid between treatments at the start of the season or through the first applications of insecticide treatments in early June. However, aphid populations did reach significantly different levels of abundance after the second insecticide treatments were applied in July. The two of the five treatments that included Delegate as a second generation codling moth application developed higher aphid populations that became significantly different by late August. Percent parasitism of walnut aphids was equal in all treatments at the start of the season, and although it declined in those plots treated with Delegate in June, this impact was not significant. However, percent parasitism did decline significantly to less than 0% following applications of Delegate in July, an impact that lasted through to early September. The greater walnut aphid populations in mid August coincided with the reduction in parasitism after application of Delegate in July. California Walnut Board 85 Walnut Research Reports 00

8 DISCUSSION As the management of primary pests in walnuts moves away from the traditional broad spectrum OP insecticides to newer reduced risk products, the impacts of these newer products on the stability of integrated pest management becomes an important concern. Evidence suggests that the newer reduced risk pesicides are not always compatible with the natural enemies that contribute very effectively to the management of secondary pests, and in some cases can be equally disruptive as the more traditional OPs. For many of these secondary pests, the consequences of changing pesticide use can be complex, as there can be differential influences of these products at the different trophic levels (pest, primary natural enemy, secondary natural enemy). From our laboratory bioassays, it is clear that although many of the newer classes of pesticides are targeted for other pests and diseases, they can also have impacts on aphids, T. pallidus and or its main hyperparasitoid S. aphidivorus. Products that have an equal impact at all three trophic levels are unlikely to be disruptive of the biological control of walnut aphid, but any that influence the wasps to a greater extent than the aphid could prove to be disruptive. Key findings from the acute bioassays are that IGRs appear to be compatible with biological control and Altacor appears to be selectively supportive of biological control, whereas Delegate, Success and Omite could be disruptive. The sublethal bioassays suggest that Warrior II could also be disruptive due to strong impacts on the daily fecundity of T. pallidus. As Warrior II does not show complete acute toxicity to the aphids its usage against codling moth could allow the aphids to escape biological control. These results indicated a clear difference in the potential disruptive potential of Delegate and Altacor as codling moth materials and these were chosen for field verification through replicated field trails. Despite the cool season and low activity of aphids in the field this year, the replicated field trial did show disruptive impacts of the Delegate applications on parasitism of walnut aphid and subsequent aphid abundance relative to control plots, although they did not lead to aphid outbreaks in the treated plots. These preliminary field observations also suggest that Delegate may be more disruptive of the biological control of walnut aphid when used against the second generation of codling moth than the first generation. These results should be treated cautiously however, as aphid numbers were so low in 00 and such effects may not be repeatable if aphid abundance is greater earlier in the season as in a more typical year. Substantial progress has also been made through the western regional USDA-SCRI project on enhancing biological control in western orchards for which this walnut project forms a matching contribution ( Delegate and Warrior II also had either acute or sublethal toxicity to western predatory mite Galendromus occidentalis, the predatory bug Deraeocoris brevis, the woolly apple aphid parasitoid Aphelinus mali, and two species of spider. While Rimon showed no acute or sublethal toxicity to T. pallidus, it did show toxicity to A. mali and to the predators tested in this broader study, indicating the need for caution in the overuse of this material. Two other important features of the selectivity of pesticides in walnut pest management are the timing of application in relation to the phenology of natural enemy flights and the development of new tools for monitoring natural enemy activity. In general, we have very little information on patterns of activity of natural enemies through the season due to the difficulty of monitoring natural enemies. It is well known that in response to California Walnut Board 86 Walnut Research Reports 00

9 herbivore attack, plants release volatile odors to attract natural enemies and these herbivoreinduced plant volatiles (HIPVs) can be developed for monitoring purposes. Results this season from the USDA-SCRI project have demonstrated that a triple combination of HIPVs can be used to monitor parasitoid, syrphid and green lacewing activity in walnut orchards (Fig. ). In addition, the seasonal pattern of activity of key natural enemies such as the green lacewing Chrysopa nigricornis and Chrysoperla carnea, and syrphids have been documented this year which will lead to the development of day degree models for these natural enemy species. The patterns arising from this work point to important differences between pest management products in terms of their selectivity with regard to walnut aphid, its primary parasitoid and hyperparasitoids. Further testing will be necessary to complete the bioassays for the hyperparasitoid and additional field tests will be needed to verify the results from this year s observations. California Walnut Board 87 Walnut Research Reports 00

10 Table. Commercial name, active ingredient and field rate of products tested in Objectives and Product Class Active ingredient Field rate (00%) Guthion OP Azinphos-methyl 0.75 lb/acre Lorsban OP Chlorpyrifos 6 fl oz/acre Asana Pyrethroid Esfenvalerate 8 fl oz/acre Warrior II Pyrethroid Lambda-cyhalothrin.56 fl oz/acre Altacor Diamide Rynaxypyr 4.5 oz/acre Cyazypyr Diamide Cyazypyr 0.5 fl oz/acre Delegate Spinosyn Spinetoram 7 oz/acre Success Spinosyn Spinosad. fl oz/acre Intrepid IGR Methoxyfenozide 8 fl oz/acre Rimon IGR Novaluron 50 fl oz/acre Omni oil Organic Omite Acaricide Propargite 0 lb/acre Kocide-Manzate Fungicide Kocide oz/acre Manzate Prostick 8.8 oz/acre Table. Effects of pesticides on natural enemies tested to date. Cell color reflects changes in natural enemy attribute: green () (< 5% reduction), yellow () (5 75% reduction), or red () (> 75% reduction); white test not yet analyzed, grey test not applicable. Natural enemy tested Altacor Cyazypyr Delegate Rimon Warrior Kumulus Kocide/Manzate type of test 0% 00% 0% 00% 0% 00% 0% 00% 0% 00% 0% 00% 0% 00% Trioxys pallidus acute 48h adult mortality chronic adult mortality fecundity sex ratio Aphelinus mali acute adult mortality Deraeocoris brevis acute 48h immature mortality acute 48h adult mortality chronic immature mortality chronic adult mortality fecundity sex ratio Galendromus occidentalis* acute 48h immature mortality acute 48h adult mortality chronic adult mortality prey consumption fecundity Pelegrina aeneola* acute 48h adult mortality chronic adult mortality fecundity Misumenops lepidus acute 48h immature mortality chronic immature mortality * Only 00% field rate used California Walnut Board 88 Walnut Research Reports 00

11 Fig.. Tritrophic comparison of the acute mortality of a range of pesticides on the walnut aphid, its primary parasitoid, and hyperparasitoid. Corrected mortality of rd instar walnut aphids, adult Trioxys pallidus, and adult Syrphophagus aphidivorus after 48h exposure to standard field rates (see Table ) of the pesticides as residues and contaminated food..0 Abbott 48h proportion killed Aphid Trioxys Syrphophagus Fig.. Projections from a stage structured matrix model that integrates the population effects of either the acute or sublethal effects of selected pesticides on individuals of Trioxys pallidus. The projections show the time delay in regrowth of T. pallidus populations from 0 to 000 individuals. Population size Control Warrior II Kumulus Cyazypyr Altacor Time in days California Walnut Board 89 Walnut Research Reports 00

12 Fig.. Seasonal abundance of walnut aphid and percent parasitism by T. pallidus in a replicated field trial of various combinations of Altacor and Delegate applied for control of first and second generation codling moth in a walnut orchard near Chico in 00. Arrows indicate timing of application and asterisks indicate dates with significant differences between treatments. Mean walnut aphids /leaflet (+SE) Altacor/Delegate Altacor/Altacor Delegate/Delegate Delegate/Altacor Control * 0 5/4 5/8 6/ 6/5 7/9 7/ 8/6 8/0 9/ 9/7 0/.4 Treatments applied. Mean percent parasitism (+SE) ** * 0 5/4 5/8 6/ 6/5 7/9 7/ 8/6 8/0 9/ 9/7 0/ Date California Walnut Board 90 Walnut Research Reports 00

13 Fig. 4. A comparative study of the suitability of a series of combinations of four HIPV volatiles (AA, AP,, and PE) for monitoring green lacewing, syrphid and parasitoid flights in a walnut orchard in Woodland in 00. Factorial study, Woodland, CA 0 5 Mean total catch/ trap/ wk (lacewings and syrphids) Green lacewings Syrphids Parasitoids Mean total catch/ trap/ wk (parasitoids) 0 Blank AA AP PE AA + AP AA + AA + PE AP + AP + PE + PE AA + AP + AA + AP + PE AA + + PE AP + + PE AA + AP + + PE 0 HIPV lure combination California Walnut Board 9 Walnut Research Reports 00