1a. Objectives (from AD-416):
The spotted wing drosophila, Drosophila suzukii (Matsumura), has been found in key California strawberry production regions, as well as, in coastal regions surrounding Pacific port terminals. Although the economic consequence(s) of this pest are unknown, experiments will be conducted to prove that this pest can be eliminated from trade and marketing channels via methyl bromide treatment using the export schedule for Australia (3lbs, 3h, >65 F), as well as, the APHIS T101-z-2 strawberry schedule (3 lbs max., 2h, 50-59 F). In addition, 4 d cold storage at 33-37 F will be explored as a nonchemical alternative for export to Mexico.
1b. Approach (from AD-416):
This project is planned in phases as indicated below. Each phase will have its own goals and these goals will feed those of the following phase. Phase I. Establish a colony of SWD at the USDA-ARS SJVASC in Parlier, CA with the throughput necessary to routinely conduct fumigation studies. Collaborator Dr. Krugner (USDA-ARS) will lead insect production; initial specimens for colony establishment will be obtained from Dr. Jana Lee (USDA-ARS). Phase II. Determine relative SWD life-stage tolerance to Australian export protocol in separate 1ft3 chambers at 65 F. Establish and report dose-mortality regressions with statistical validity (Probit v. 2007 software). Phase III. Perform confirmatory fumigations for Australian export in triplicate 9ft3 chambers with 10,000 SWD specimens (most tolerant stage) while fruit is packed in export boxes recommended by industry. To ensure adequate exposure for complete mortality, fumigant concentrations will be measured throughout fumigations. Sorption and box effects on fumigation will be quantitatively analyzed. Phase IV. Determine mortality of SWD eggs, larvae, pupae, and adults to 1) methyl bromide at T101-z-2 doses in separate 1ft3 chambers at 50, 60, and 70 F, and 2), 4 d cold storage at 33-37 F to simulate the shipping scenario to Mexico. Establish and report dose-mortality regressions with statistical validity (Probit v. 2007 software). Phase V. Perform confirmatory cold-storage treatments in refer units with 10,000 SWD specimens (most tolerant stage) while fruit is packed in export boxes recommended by industry. To ensure adequate exposure for complete mortality, fumigant concentrations will be measured throughout fumigations. Sorption and box effects on SWD mortality will be quantitatively analyzed. Phase VI. Phytotoxicological Analysis Determine potential phytotoxicity to strawberries that occurs from exposure to fumigants at dosages that are efficacious for killing the most tolerant SWD life stage.
3. Progress Report:
This Reimbursable Cooperative Agreement was established to support Objective 1 of the in-house project and is related to finding methyl bromide alternatives for postharvest applications. Spotted wing drosophila (SWD), Drosophila suzukii, is a pest of concern to countries that import strawberries from California. Methyl bromide fumigation is required to export strawberries to Australia, which has an estimated value of 20 million USD annually. US industry wanted to explore the potential of meeting the phytosanitary requirements of Australia at a treatment temperature lower than 18.0 °C, the current requirement. New data demonstrated that methyl bromide fumigations were effective at pulp temperature of 12.8 °C, as we observed complete mortality of approximately 100,000 internal feeding third instar larvae (ca. 60 to 108-h old at fumigation), the most methyl bromide-tolerant SWD life stage.