Exploring the efficacy and mechanisms of a crop sterilant for reducing infestation by spotted-wing drosophila (Diptera: Drosophilidae)

Authors: VAN TIMMEREN, STEVE - Michigan State University; FANNING, PHILIP - Michigan State University; SCHONEBERG, TORSTEN - University Of Maryland; HAMBY, KELLY - University Of Maryland; Lee, Jana; ISAACS, RUFUS - Michigan State University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2019
Publication Date: 1/31/2020
Citation: Van Timmeren, S., Fanning, P.D., Schoneberg, T., Hamby, K., Lee, J.C., Isaacs, R. 2020. Exploring the efficacy and mechanisms of a crop sterilant for reducing infestation by spotted-wing drosophila (Diptera: Drosophilidae). Journal of Economic Entomology. 113(1):288-298. https://doi.org/10.1093/jee/toz245.
DOI: https://doi.org/10.1093/jee/toz245

Interpretive Summary: The spotted wing drosophila (SWD), originally from Asia, has become a global economic pest of small fruits and cherries. A reliance on chemical controls has increased management costs, caused secondary pest outbreaks and insecticide resistance in field populations, and raised concern about exported fruit being rejected at port due to insecticide residuals. Growers have expressed strong interest in sustainable tactics to reduce reliance on insecticides, especially for organic systems. An organic approved crop sterilant was found to reduce SWD infestation in small field trials. Follow-up studies in the lab show that the sterilant does not kill adults nor prevent pest eggs from hatching, but inhibits yeast growth, and reduces the attractiveness of fruit for flies to settle on or lay eggs on. This additional tool will help organic growers greatly since they have few compounds to control SWD, and avoid over-reliance on the most common insecticide. Field populations in California have already shown resistance to this organic insecticide.

Technical Abstract: Vinegar flies (Diptera: Drosophilidae) are well known to be associated with yeasts, which provide important nutrients and emit attractive semiochemicals. Drosophila suzukii (Matsumura) has become a major pest of berries and cherries around the world, requiring intensive management to maintain fruit quality. While insecticides remain a dominant control approach, disruption of fly-yeast-host interactions remains a promising avenue for reducing the economic impact of this pest. We conducted field and laboratory experiments to explore whether a crop sterilant (peroxyacetic acid and hydrogen peroxide) developed for disease control can affect D. suzukii. In two years of field tests in highbush blueberries, we found significantly lower infestation by D. suzukii in plots treated with the sterilant, both alone and in a rotation program with zeta-cypermethrin. When shoots from treated plots were tested in no-choice bioassays, sterilant treatments did not affect adult mortality or oviposition, but they reduced infestation. To explore the mechanisms in the laboratory, we found that the sterilant did not affect adult mortality, nor oviposition on treated fruit under no-choice settings, but adult flies settled and oviposited less on treated fruit in choice settings. When the sterilant was applied to colonies of Hanseniaspora uvarum and Issatchenkia terricola yeasts that are attractive and provide nutrition to D. suzukii, there was a dose-dependent inhibition of their growth. We highlight the potential for microbial management as a component of IPM programs, and prioritize research needs to incorporate this approach into control programs.