Determining Field Insecticide Efficacy on Whiteflies with Maximum Dose Bioassays

SIMPLE SUMMARY: The sweet potato whitefly is a major pest of crops worldwide, causing significant damage. To control this pest, farmers often use insecticides, but the effectiveness of these treatments can vary depending on resistant population dynamics. We investigated the efficacy of insecticides on adult whiteflies in the field and laboratory conditions using maximum labeled rate methods. Fast-acting insecticides were more effective in controlling whitefly adults, and bioassays could be an effective tool for determining efficacy prior to expensive field applications. These findings will be valuable to farmers and researchers seeking to optimize control strategies for whiteflies, helping to reduce crop damage and improve yields. ABSTRACT: We conducted a rapid bioassay method to assess insecticide efficacy for controlling adult sweetpotato whitefly Bemisia tabaci in squash and cucumber crops before insecticide applications. The study aimed to evaluate the accuracy of a 24-hour laboratory bioassay in determining maximum dose insecticide efficacy in the field. Ten insecticides were evaluated using leaf-dip bioassays, and their effectiveness was tested across eight cucurbit field experiments in Georgia, USA, during the 2021 and 2022 field seasons. The maximum dose, defined as the highest labeled rate of an insecticide diluted in the equivalent of 935 L ha(−1) of water, was used for all bioassays. Adult survival observed in the bioassay was compared to adult field count-based survival 24 h after treatment. A low concentration (1/10 rate) was used for imidacloprid, flupyradifurone, pyriproxyfen, and cyantraniliprole to assess insecticide tolerance in the whitefly population. Overall, significant positive correlation between laboratory bioassay and field efficacy was reported, explaining 50–91% of the observed variation. The addition of the low dosage was helpful, indicating that no rate response was consistent with susceptibility to the tested insecticide, while a rate response was associated with a loss of susceptibility between 2021 and 2022.