Performance of novel alternatives to neonicotinoid insecticide seed treatments for managing maggots (Diptera: Anthomyiidae) in large-seeded vegetable crops

Abstract

Maggots [Delia spp. (Diptera: Anthomyiidae)] are pests of large-seeded vegetable crops such as snap bean, dry bean, and sweet corn. Economically damaging infestations of Delia spp. can be sporadic and difficult to predict, but typically occur early in the spring when soil conditions are cool and wet. Larval feeding can substantially reduce plant stands and compromise normal plant vigor and development. Neonicotinoid insecticide seed treatments are currently used to protect large-seeded vegetable crops from Delia spp, but concerns regarding their negative impacts on beneficial insects and the environment have stimulated interest in identifying effective non-neonicotinoid seed treatments. From 2021 to 2024, field studies in the northeastern, midwestern, and pacific northwestern USA evaluated non-neonicotinoid insecticide seed treatments belonging to the spinosyn, anthranilic diamide, and isoxazoline classes for managing Delia spp. in snap bean, dry bean, and sweet corn. Results indicated that cyantraniliprole and spinosad provided a similar level of Delia spp. control as thiamethoxam, the neonicotinoid standard, in snap bean. None of the alternatives were as effective as thiamethoxam for Delia spp. control in dry bean. In contrast, all non-neonicotinoid insecticides such as chlorantraniliprole, cyantraniliprole, isocycloseram, spinosad, and tetraniliprole were effective in protecting sweet corn from Delia spp. Most of these non-neonicotinoid options are not currently approved for commercial use on these crops, but our results could help support future registrations. Adoption of non-neonicotinoid seed treatments for Delia spp. control also must consider their efficacy against other common early-season insect pests, risk to pollinators and other non-target organisms, and cost.