1a. Objectives (from AD-416):
Evaluate and develop postharvest treatments such as methyl bromide, CO2/SO2, phosphine, ozone, ultralow oxygen and cold treatments to eliminate invasive pests of concern to the California table grape industry that serve as trade barriers. The invasive pests of concern are spotted wing drosophila (SWD)(Drosophila suzukii), European grapevine moth (EVGM)(Lobesia botrana), and the newest invasive, the brown marmorated stink bug (BMSB)(Halyomorpha halys).
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. Maintain colonies of SWD at the USDA-ARS SJVASC in Parlier, CA, with the throughput necessary to conduct fumigation studies. Phase II. Most tolerant life stage and dose/mortality – tests will be conducted to determine the most tolerant stage of invasive pest (eggs, larvae, pupae, and/or adults) towards a given treatment (fumigant or cold storage) by evaluating mortality over a range of treatment conditions (e.g., doses or temperatures). Establish and report dose-mortality regressions with statistical validity (Probit v. 2007 software). Phase III. Perform confirmatory fumigations in triplicate 9 1ft3 chambers with 10,000 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. Identify any potential phytotoxicity to grape berries that occurs from exposure to fumigants at dosages that are efficacious for killing the most tolerant invasive pest life stage.
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. Spotted wing drosophila (SWD), Drosophila suzukii (Matsumura)(Diptera: Drosophilidae), is a pest of concern to certain countries that import table grapes from California USA. Table grapes were removed from commercial boxes intended for export, berries were infested with SWD, and buried in commercial loads. Fumigations were conducted at 15.6 ± 0.6°C for 30 min with a SO2 and CO2 mixture (1:6% vol.), followed by refrigeration at -0.5 ± 0.7°C for 6 d. The combination treatment resulted in 1 survivor out of 93,512 ± 2,427 (n ± s) specimens when adult emergence from non-fumigated as well as non-refrigerated controls, were used to determine the total number treated. Data on SWD development as well as adult emergence from fumigated berries were used to identify the most fumigant-tolerant timespan of development and estimate the fraction of treated specimens within the most fumigation-tolerant timespan of development that would be entering into cold-treatment (62,434 ± 2,427)(n ± s). In addition data were used to estimate the relative probability distribution of life stages at the time of fumigation that ultimately emerged during the most fumigation-tolerant timespan of development (eggs = 0.095, 1st instar = 0.153, 2nd instar = 0.205, 3rd instar = 0.514, and pupae = 0.032).