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Project description

Pheromone mating disruption programs for codling moth in walnuts: Developing and optimizing hand applied meso-emitters. (07BU012)
Program UC IPM competitive research grants program
S.C. Welter, Insect Biology, UC Berkeley
Host/habitat Walnuts; Pears
Pest Codling moth Cydia pomonella
Discipline Entomology
Biorational Use of Biotic Agents or Chemicals
Start year (duration)  2007 (Three Years)
Objectives Development of a cost-effective pheromone mating disruption program for codling moth in walnuts using significantly fewer pheromone dispensers releasing at intermediate rates so as to reduce labor requirements.

a. Optimization of number of pheromone point sources b. Optimization of emission rates per dispenser c. Demonstration of optimized program in two walnut growing districts

A modified approach is proposed for managing codling moth in walnuts using hand-applied pheromone dispensers that emit higher rates of codlemone per dispenser requiring fewer units per acre. Simple changes to existing commercial products might include changes in dispenser size or polymer type restricting emission. Savings might result from reduced application costs and potentially reduced total pheromone required. The reduction in dispensers, hopefully to less than 15 per acre, would allow pheromone mating disruption to be feasible for the large canopies of mature trees in which 400 ties per acre has proven logistically too daunting for growers.
Two commercial products have now been developed from our research with the "ring" meso-dispensers already submitted for registration by Pacific Biocontrol to the EPA. The second product, the Suterra Meso membrane dispenser, is expected to be submitted for registration within the next 2 months. Because the number of pheromone emitting units is 20 or less per acre, labor requirements for the application of the dispensers appear to be reduced by approximately 80% in walnuts compared to a traditional pheromone hand-applied program. There was no evidence of performance decline in plots treated with either the ring or membrane meso-emitter compared to plots with traditional pheromone programs using 160-200 units per acre. While higher moth counts occur in meso-treated plots, no significant difference in damage was observed. Codling moth damage was significantly depressed by both meso-emitter treatments (P=0.052). While the explicit rate trial failed to generate significant enough codling moth pressure to adequately challenge the low-rate emitters, the more qualitative comparison of the ring and membrane mesos suggested that the 50% reduction in pheromone did not impact the performance negatively. Some early projections on pricing suggest a potential significant savings may be possible if the reduced levels of pheromone in the ring dispenser continue to look promising. Large-scale demonstrations are being conducted in 2010 in multiple regions of California using both the ring and membrane meso-dispensers.

We continued trials of pheromone meso-emitters that emit higher levels of pheromone per dispenser than current hand-applied dispensers. Field trials in 2007 suggested that meso-emitters deployed at rates as low as 18 units per acre in a combination program — using pheromone plus insecticide supplementation — provided superior codling moth control compared to the insecticide-only program. This improved control was achieved with at least a 90% reduction of pheromone point sources compared to a standard application of 180 to 200 units per acre. Our goal in 2008 studies was to use the 18-unit per acre deployment rate but vary total emissions per acre through the use of dispensers with different emission rates to determine the pheromone load necessary to affect codling moth control. Four experimental meso-emitter treatments and a Checkmate CM XL1000 application in combination with the grower program were contrasted with the grower insecticide program alone in a replicated block trial. Grower treatments ranged from 0 to 4 insecticide applications. No pattern was observed between the projected rate of pheromone emission and trap counts. Traps baited with the 1x lures were suppressed throughout the entire growing season for all treatments in comparison to the grower standard. August canopy samples indicated low levels of codling moth damage, ranging from 0 to 1.0% with no consistent pattern across treatments. Average codling moth damage in the harvest samples ranged from 0.25to 0.7% with no clear pattern and no significant treatment effect observed. Codling moth pressure in the 2008 trial sites appeared low so that potential differences between treatments could not be determined. The trial should be repeated under greater codling moth pressure as defined by damage levels from 2008 damage assessment at the handlers. If the application rate of 18 dispensers per acre and reduced pheromone loads in the dispensers demonstrate treatment benefits, this research may provide an economic and logistically feasible pheromone program for the walnut industry.

New pheromone meso-emitters that emit higher levels of pheromone per dispenser than current hand-applied dispensers were developed and tested in 2007. Based on winter data developed in the lab by Suterra, the meso-emitters were deployed at lower rates of 12 to 60 point-sources per acre, compared to the traditional 180 dispensers per acre.

Total pheromone emitted per acre exceeded or equaled the emission rate of the conventional Checkmate pheromone program for the entire season. In walnut trials with moderate pressures, the meso-emitters provided significant reductions in codling moth damage compared to the control. A study looking at the effects of number of point- sources per acre, no significant advantage was observed when the number of point-sources per acre was increased from 12 to 60 points per acre. However, a slight, but statistically nonsignificant increase in codling moth was noted for the 12 point-source per acre treatment. The 18 point-source treatment was equal to the 180 point-source commercial standard pheromone treatment, Checkmate. Both treatments, which also had the grower insecticide management program overlaid, showed a statistically improved control program over the grower insecticide program alone.

If repeated in future years, the 90% reduction in the number of dispensers per acre should make this program economically and logistically feasible for walnut orchards. If additional reductions in the amount of pheromone per acre can be reduced, the potential reductions of product cost could also be significant.

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