1a. Objectives (from AD-416):
Quantify spotted wing drosophila distribution in geographically distinct Western U.S. commercial stone fruit orchards, index this distribution relative to other suitable host crops, and enumerate the probability of SWD removal and/or mortality as a function of harvesting, cleaning, packing, and shipping procedures employed by the stone fruit industry, particularly with respect toward Australian and New Zealand export. In addition, low-temperature high-concentration phosphine fumigation will be evaluated for its technical and economic potential to serve as a final element of mitigation against spotted wing drosophila.
1b. Approach (from AD-416):
This project is planned in 3 compounding phases as indicated below with corresponding objectives and hypotheses. Phase 1, year 1. Perform host trials to demonstrate status in peach, plum, nectarine and apricot for spotted wing drosophila and designate categories of host preference (such as, stage of maturity, commercial export grade or physical condition of the fruits) in stone fruits. Phase 2, year 2. Design, refine and execute experiments that allow spotted wing drosophila population densities to be traced through chemical and physical processes that are consistent with Western US stone fruit production and distribution to Australian and New Zealand markets. Phase 3, year 3. Determine the mortality of spotted wing drosophila eggs, larvae, pupae and adults in infested stone fruit, as well as, the phytotoxicological impact that results from Vaporphos phosphine at 3-5 C and index relative to methyl bromide at 15.6 C.
3. Progress Report:
This Trust agreement was established to support Objective 1 of the in-house project and is related to finding postharvest methyl bromide alternatives and techniques for improving methyl bromide fumigations. The spotted wing drosophila (SWD) is a polyphagous insect pest that is of concern to certain countries that import peaches and nectarines from California. Researchers developed a Host Potential Index (HSI) that ranks the relative potential of peaches at different points of maturation to serve as a SWD host. Peaches were picked from orchards two weeks prior to harvest, at the time consistent with commercial harvest, and two weeks following harvest. Peaches, at the different maturities, were then ranked as a SWD host using three independent experiments that distinguish key elements of SWD behavioral biology pertaining to host location, selection, and utilization. Results indicate that the potential for peaches to serve as SWD hosts increased with maturation and that no SWD adults emerged following a forced-infestation of peaches with maturity consistent to that of commercial harvest in California. This research will be used to support USDA-Animal and Plant Health Inspection Service, USDA-Foreign Agriculture Service, and United States Trade Representative in efforts to retain and expand the trade of California peaches and nectarines to Australia and New Zealand, which collectively have an estimated value of 60 million USD annually.