Wireworm (Coleoptera: Elateridae) Species Composition and Management in Sweet Potato Grown in North Florida Using Chemical Insecticides and Entomopathogenic Nematodes.

Wireworms are immature stages of click beetles (Coleoptera: Elateridae) and are considered a serious threat to sweet potato production in the southern United States. The major wireworm species collected in North Florida sweet potato fields in 2017 and 2018 were Conoderus scissus, C. rudis, C. amplicollis, and C. falli. These species vary in their behavior and biology. During a 2-yr study period, we conducted two insecticide field trials using eleven insecticides belonging to organophosphates, neonicotinoids, pyrethroids, and botanical classes, and three field trials using entomopathogenic nematode (EPN) species to control wireworms. In 2017, all insecticide treatments significantly reduced new feeding holes and total holes (old + new + other) as compared to the untreated control. In 2018, the result was similar with a few variations. In both years, all insecticides showed a percentage reduction in wireworm damage holes (2017: 34.88-96.19%; 2018: 12.38-97.02%) with the highest by Regent. In the EPN field study, one application of EPN near planting significantly reduced soil insects. In a laboratory study conducted at the Tropical Research and Education Center, UF-IFAS, chlorpyrifos caused higher percentage mortality of C. rudis (55.5%) than C. scissus (22.2%). At the present experiment rates, none of the insecticides caused the mortality of C. amplicollis. Heterorhabditids strain 'FL-2122' was more susceptible to chlorpyrifos than other strains of EPN.