Research Entomologist USDA-ARS Moxee, Washington, United States
Both conventional and organic apple orchardists are examining non-chemical methods for controlling their pests. Chemical control of mealybugs can be particularly challenging even in conventional orchards, as non-mobile stages have minimal exposure to pesticide residues and coverage on areas where mealybugs aggregate (e.g. bark crevices) can be difficult to achieve. Many orchardists have experimented with releasing natural enemies for various pests, but are uncertain of which natural enemies, timings, release rates, or techniques should be used. This can leave biocontrol practitioners trying multiple strategies and hoping something works, which is an inefficient use of their time and resources. In order to improve recommendations for augmentative releases, we compared efficacy of releasing mealybug destroyers (Cryptolaemus montrouzieri) at two timings (early and mid-season), two rates (1,000 or 2,000 per acre), and releases by drone and by hand. We also tested three methods for monitoring the mealybug destroyers post release: sticky cards, burlap bands, and tap counts. All methods tested reduced mealybug counts for at least one week post-release. Preliminary analysis indicates both rates and timings performed equally well, but drone releases may be slightly less effective than hand releases. Better monitoring tools are needed to track mealybug destroyer abundance after release, as recapture was very rare. Future work will focus on release timing and drone use in larger plots.
