Ethyl formate fumigation and ethyl formate plus cold treatment combination as potential phytosanitary quarantine treatment of Drosophila suzukii in blueberries

Authors: KWON, TAE - Gyeongsang National University; PARK, CHUNG - Gyeongsang National University; LEE, BYUNG-HO - Gyeongsang National University; Zarders, Dominique; ROH, GWANG - Oak Ridge National Laboratory; Kendra, Paul; Cha, Dong

Submitted to: Journal of Asia Pacific Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2020
Publication Date: 12/8/2020
Citation: Kwon, T.H., Park, C.G., Lee, B., Zarders, D.R., Roh, G.H., Kendra, P.E., Cha, D.H. 2020. Ethyl formate fumigation and ethyl formate plus cold treatment combination as potential phytosanitary quarantine treatments of Drosophila suzukii in blueberries. Journal of Asia Pacific Entomology. 24(1):129-135. https://doi.org/10.1016/j.aspen.2020.11.008.
DOI: https://doi.org/10.1016/j.aspen.2020.11.008

Interpretive Summary: As a widespread invasive species of cherries and berries, spotted wing drosophila (SWD) has become a a serious quarantine pest in trade of berries. Currently methyl bromide (MB) fumigation at >18°C is sole practical phytosanitary treatment option. Researchers at USDA-ARS in Hilo, Hawaii and Gyeongsang National University in South Korea are developing MB alternative treatment options to control SWD in blueberries. Ethyl formate, a safe MB alternative fumigant, was effective at controlling all life stages of SWD at both 5 and 21°C and did not reduce the quality of blueberries. A combination of a much weaker dose of EF and cold treatment at 5°C was also effective at controlling SWD. Since cold chain is required to maintain quality of berries throughout postharvest to consumer, both stand-alone EF treatment at 5°C and combination of low dose EF treatment followed by cold storage at 5°C could be effective options for phytosanitation of SWD in blueberries.

Technical Abstract: Spotted wing drosophila, Drosophila suzukii (Diptera:Drosophilidae), is a serious invasive pest of berries and cherries in U.S and Europe and has become a major phytosanitary trade barrier. Here we evaluated the potential use of ethyl formate (EF) and/or cold treatment for the postharvest control of D. suzukii in blueberries. EF fumigations were effective against D. suzukii. LCt99% of EF for eggs, the most tolerant life stage, were 207.7 and 168.5 g h m-3 at 5 and 21°C, respectively. In confirmatory scale-up (10 m3) trial conducted at 5°C, complete control of 1,332 D. suzukii eggs placed inside and outside of blueberry boxes was achieved using 70 g m-3 EF for 4 h with 5% blueberry loading ratio with no significant reductions in deterioration rate and soluble sugar content of blueberries. In small scale experiments, up to 9-d stand-alone cold treatment at 5°C was effective for controlling 100% of 60 each of D. suzukii eggs and larvae but not for pupae. The efficacy of this cold treatment could be improved by treating D. suzukii eggs using low lose EF (LCt50% level) prior to the cold treatment. The combination treatment resulted in complete mortality of 60 each of D. suzukii eggs, larvae, and pupae after 5, 7, and 7-d of cold treatment, respectively. Together, our results suggest that EF treatment or the combination treatment of low dose EF and cold as a systems approach may be a viable option for postharvest control of D. suzukii in blueberries.