Phagostimulant bait sprays improve control of spotted wing drosophila (Drosophila suzukii) in soft fruit

By attracting and stimulating feeding on spray droplets, phagostimulant baits provide an opportunity to increase the efficacy of crop protection products against the spotted wing drosophila (Drosophila suzukii). Here, we examined the use of a high-sugar, plant-derived bait (ProBandz ® , PB) in combination with low dose insecticides and an entomopathogenic fungus Metarhizium anisopliae strain 35.79 for control of D. suzukii. We compared the efficacy of treatments in laboratory jar bioassays and in semi-field strawberry experiments using laboratory D. suzukii cultures, and in field strawberry and raspberry experiments on natural D. suzukii infestations. M. anisopliae 35.79 increased D. suzukii mortality in jar bioassays but did not affect oviposition. There was no evidence that combining M. anisopliae 35.79 with PB led to increased efficacy, and in a semi-field experiment this combination led to an increase in D. suzukii larvae in fruit. Deltamethrin in PB droplets was effective in increasing mortality and reducing oviposition in jar bioassays but deltamethrin + PB bait sprays were ineffective in a field raspberry experiment. PB increased the D. suzukii control efficacy of lambda-cyhalothrin in jar bioassays. Low volume bait sprays with 8% of the full field rate of lambda-cyhalothrin in semi-field and field strawberry experiments were as effective in controlling D. suzukii as full rate, high volume insecticide sprays but without causing pesticides residues in the fruit. This work will provide evidence supporting the reduction of dependence and risk of resistance to the two main insecticides used for D. suzukii control: spinosad and cyantraniliprole.