Field efficacy of conventional and biological insecticides for control of picture-winged flies (Diptera: Ulidiidae) in Florida sweet corn

Picture-winged flies (Diptera: Ulidiidae) locally referred to as corn silk flies are the most damaging insect pests feeding on sweet corn in southern Florida. Adults of three silk fly species, Chaetopsis massyla (Walker), Euxesta eluta Loew, and Euxesta stigmatias Loew, lay eggs on silks, resulting in maggot-infested ears. Silk fly management relies on frequent foliar applications of pyrethroids targeting the adults; however, unacceptable maggot infestations still occur even when silk flies are intensively managed. Thus, management with pyrethroids needs to be complemented with additional tactics. Three field evaluations were conducted in spring 2021 to determine the efficacy of registered and non-registered conventional and biological insecticides. Insecticide treatments were applied once every other day for two weeks starting at first silk. In a first experiment, thiamethoxam and abamectin mixed with lambda-cyhalothrin were evaluated. In a second experiment, azadirachtin, Beauveria bassiana strain GHA, and Chromobacterium subtsugae strain PRAA4-1^T were evaluated alone and tank-mixed with lambda-cyhalothrin. In a third experiment, the efficacy of dinotefuran and cyantraniliprole, alone and tank-mixed with zeta-cypermethrin, were compared to the efficacy of zeta-cypermethrin, beta-cyfluthrin, bifenthrin, and lambda-cyhalothrin. Pyrethroids reduced silk fly injury or infestation levels in all three experiments. However, the potential benefits of applying other conventional or biological insecticides were not observed.