Efficacy of organic and conventional insecticides for Drosophila suzukii when combined with erythritol, a non-nutritive feeding stimulant

Spotted-wing drosophila (Drosophila suzukii; SWD) is an economically important insect pest of small and soft skinned fruit. Female SWD use a heavily sclerotized ovipositor to deposit eggs in ripening fruit. After emergence from eggs, larval feeding and development damages fruit and results in yield loss. The most prevalent management strategy continues to be regular applications of broad-spectrum insecticides. Since the arrival of SWD and the subsequent increase of insecticidal sprays, producers are challenged to balance goals related to pest and pollinator management, the environment, and finances. Growers need additional management tools in order to reduce environmental risks and to adhere to label specifications. To this end, we investigated the efficacy of novel chemical controls alone and with the addition of feeding stimulants and surfactants, compared to standard insecticide products typically used for pest management by fruit growers. We conducted a series of laboratory bioassays to test four organically approved insecticides, three conventional insecticides, one feeding stimulant and five adjuvants. We measured the effects of these products on SWD adult mortality, oviposition, larval and pupal development, and adult emergence. Nine of the 25 treatments significantly increased adult mortality after 24 h of exposure and only three of the 25 treatments significantly reduced oviposition. The addition of erythritol [1.75 M] to some marginally effective insecticides increased their efficacy, while decreasing the efficacy of others. This information will guide future research and result in recommendations for both organic and conventional growers for sustainable management of this invasive pest.