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Project description

Improving the Technology of Trichogramma Augmentation Against Codling Moth in Walnuts in California. (95BC003)
Program UC IPM competitive research grants program
N.J. Mills, Environmental Science, Policy and Management, UC Berkeley
Host/habitat Walnuts; Tree Crops
Pest Codling Moth Cydia pomonella
Discipline Entomology
Trichogramma platneri
Biological Controls
Start year (duration)  1995 (One Year)
Objectives Develop a ground delivery system to broadcast an even dispersion of Trichogramma platneri through the canopy of a commercial walnut orchard.

Evaluate the survival and performance of T. platneri through each step of the delivery system.

Determine the pattern of distribution of parasitized eggs within the tree canopy and the parasitoid emergence rate after broadcast application from the ground.

Evaluate the effectiveness of T. platneri augmentation against codling moth in replicated field trials, comparing broadcast and point source release.

Demonstrate season-long control of codling moth using the most effective strategy for augmentative releases of T. platneri in several commercial walnut orchards.

Final report In order to make the application of Trichogramma in walnut orchards more efficient and acceptable to growers, it is important to be able to develop a broadcast application technique that will deliver the Trichogramma parasitized eggs of Ephestia kuehniella into the canopy of the orchard from a tractor-mounted spray applicator. In this project we tested a commercially available Bio-Sprayer designed for delivering benefical insects on the tree foliage. The Bio-Sprayer system applies a slurry of Trichogramma parasitized eggs in a Bio-Carrier solution that sticks them to the orchard foliage.

Although submersion in water did not affect emergence of Trichogramma from parasitized eggs, the parasitized eggs did not survive more than 2 hours after being submerged in a solution of Bio-Carrier. However, aeration of the Bio-Carrier solution significantly enhanced the survival of the parasitized eggs. The flow rate from a single arm of the BioSprayer was about 277ml/minute, but the concentration of parasitized eggs in the slurry emerging from the sprayer was only 35% that of the concentration placed into the spray tank, due primarily to eggs sticking to the walls of the tank. The pattern of distribution of parasitized eggs broadcast by the sprayer varied with distance from the spray arm and height.

Parasitized eggs were found in small batches, rather than singly, after application with the BioSprayer and the emergence rate of Trichogramma adults from these eggs was reduced by about 60%. It was found that the spray arms need to be set at an angle of 75° above horizontal to gain maximum coverage of application for the typical height and row spacing of a walnut orchard, and that release rates be increased by a factor of five to allow for reduced flow rate and survival.

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