Risk of Spotted-Wing Drosophila Injury and Associated Increases in Acetic Acid in Minnesota Winegrapes

Dominique N Ebbenga,W.D Hutchison,Matthew D Clark,Eric C Burkness

doi:10.5344/ajev.2020.20008

Abstract

Spotted-wing drosophila, Drosophila suzukii (Matsumura), is an invasive species to Minnesota that was first recorded in 2012, and since its arrival has become a major pest of stone fruit and berry crops, including winegrapes. High fecundity and short generation times have allowed D. suzukii to flourish and spread throughout North America and Europe in a relatively short period of time. Laboratory and field trials were conducted during 2017-2019 to determine the risk of injury from D. suzukii in Minnesota winegrape varieties and to assess acetic acid (AA) levels in wine and juice samples from cold-hardy winegrape varieties in Minnesota. Results from risk of injury studies in 2017 and 2018 demonstrated a low risk of direct injury to intact grape berries. Winemakers, however, are concerned about the potential risk of D. suzukii infestations increasing AA producing bacteria (e.g., Acetobactor spp.), known to expedite the development of sour rot in grapes. Acetic acid trials in 2017 and 2019 demonstrated significant increases in AA for select grape varieties as fly density increased. However, the 2018 AA trials with modified infestation protocols did not result in significant differences in AA. Our results are discussed within the context of improving integrated pest management programs (IPM) for D. suzukii.

Highlights

Spotted-wing drosophila, Drosophila suzukii (Matsumura), is an invasive species to Minnesota that was first recorded in 2012
Our study to assess the possibility of direct injury by D. suzukii in cold-hardy winegrapes in both 2017 and 2018 demonstrated that there is a low risk of injury, with numerous winegrape varieties having zero or very low larval/pupal infestations when intact berries are exposed to D. suzukii (Tables 1 and 2)
The results for several Minnesota cold-hardy varieties evaluated in this study indicate a low risk of injury from D. suzukii when grapes are managed well to minimize splitting and damage by birds or insects that may compromise the berry exocarp

Summary

Introduction

Spotted-wing drosophila, Drosophila suzukii (Matsumura), is an invasive species to Minnesota that was first recorded in 2012. Since its arrival it has become a major pest of stone fruit and berry crops, including winegrapes. Winemakers, are concerned about the potential risk of D. suzukii infestations increasing AA-producing bacteria (e.g., Acetobacter spp.), known to expedite the development of sour rot in grapes. Drosophila suzukii (Matsumura), commonly known as spotted-wing drosophila, is an invasive species native to East Asia (Walsh et al 2011, Daane et al 2016) and has become a major pest of berry crops in all new countries where it has invaded. D. suzukii was first recorded in North America in 2008 (Hauser 2011).

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Discussion

Conclusion