Evaluation of organic insecticides for management of spotted‐wing drosophila (Drosophila suzukii) in berry crops

Abstract

Spotted‐wing drosophila, Drosophila suzukii (Matsumura), is an invasive pest affecting fruit production in many regions of the world. Insecticides are the primary tactic for controlling D. suzukii in organic as well as conventional production systems. Organic growers have a greater challenge because fewer insecticides are approved for use in organic agriculture. The most effective organically approved product is spinosad, but alternatives are needed because of label restrictions limiting the number of applications per year, toxicity to beneficial arthropods and the risk of developing resistance. We evaluated several organically approved insecticides against D. suzukii in laboratory assays and field trials conducted on organic blueberry and raspberry farms. Spinosad was consistently the most effective insecticide, but a few other insecticides such as azadirachtin + pyrethrins, Chromobacterium subtsugae and sabadilla alkaloids showed moderate activity. None of the treatments had long residual activity. Mortality started to decline by 3 days after treatment, and by 5 days after application, the treatments were not different from the controls. These products may be useful in rotation programmes, necessary for reducing reliance on spinosad and mitigating resistance. Cultural and biological control approaches are needed in fruit production for D. suzukii management, but insecticides will likely continue to be the dominant management tactic while these other approaches are being optimized and adopted.

Combining sterile and incompatible insect techniques for the population suppression of Drosophila suzukii

“…Insecticide applications are currently the front-line method used to control D. suzukii in conventional and organic crop areas (Beers et al 2011;Bruck et al 2011;Grassi et al 2011;Rota-Stabelli et al 2013;Sial et al 2019;Van Timmeren and Isaacs 2013). Application of insecticides close to the harvest period poses great concerns for the health of both farmers and consumers (Rota-Stabelli et al 2013), but also to beneficial arthropods (Desneux et al 2007).…”

“…Application of insecticides close to the harvest period poses great concerns for the health of both farmers and consumers (Rota-Stabelli et al 2013), but also to beneficial arthropods (Desneux et al 2007). The total number of applications for most insecticides is restricted by regulation but, on the other hand, the short generation time of D. suzukii requires frequent applications when fruits are at the ripening stage which needs chemicals with a shorter pre-harvest interval (Cini et al 2012;Goodhue et al 2011;Sial et al 2019). This can result in increased insecticide residuals in fruits and unpredictable impacts on pollinators and other non-target species, including D. suzukii's natural enemies (Iglesias and Liburd 2017;Rota-Stabelli et al 2013;Roubos et al 2014;Walsh et al 2011).…”

Evaluation of non‐target effects of OMRI‐listed insecticides for management of Drosophila suzukii Matsumura in berry crops

“…The spotted wing drosophila (SWD), Drosophila suzukii Matsumura ( Diptera : Drosophilidae ), is an invasive fruit fly and an economic threat to fruit industries throughout North America (Hauser, ; Lee, Bruck, Curry, et al, ; Lee, Bruck, Dreves, et al, ; Walsh et al, ), Europe (Calabria, Máca, Bächli, Serra, & Pascual, ; Cini, Ioriatti, & Anfora, ) and South America (Deprá, Poppe, Schmitz, De Toni, & Valente, ). Frequent insecticide applications are made to minimize D. suzukii infestations in berry crops (Sial et al, ; Van Timmeren & Isaacs, ). Extensive use of insecticides throughout the growing season can disrupt natural enemy populations, resulting in reduced fecundity, longevity and development rates of biological control organisms (Croft & Brown, ; Desneux, Decourtye, & Delpeuch, ).…”

“…There has been increasing availability of reduced‐risk insecticides with more selectivity in fruit crops (Isaacs, Mason, Brewer, Noma, & 'Neal, ), especially in organic production (Sial et al, ). Reduced‐risk insecticides have several advantages over broad‐spectrum insecticides including shorter pre‐harvest intervals due to their lower mammalian toxicity and greater compatibility with biological control tactics due to their less harmful effects on natural enemies (Atanassov, Shearer, & Hamilton, ; Liburd, Arevalo, & Rhodes, ; Roubos, Rodriguez‐Saona, & Isaacs, ).…”

“…Spinosad has been shown to be the most effective organically approved insecticide for D. suzukii management (Beers, Steenwyk, Shearer, Coates, & Grant, ; Bruck et al, ; Sial et al, ; Van Timmeren & Isaacs, ), and in some cases, the effectiveness of other selective organic insecticides may not be enough to meet the challenges associated with this aggressive pest (Cini et al, ). Previous research has indicated that azadirachtin + pyrethrins, Chromobacterium subtsugae , and sabadilla alkaloids cause some mortality in D. suzukii populations and could be useful in rotations with spinosad.…”