D3505: Residual activity of the most common insecticides used in the Mississippi Delta to control tarnished plant bugs in cotton

The tarnished plant bug is a key pest of cotton in the mid-south and some areas of the eastern U.S. Its control has been solely based on chemical insecticides and is rapidly becoming resistant. This study was conducted over a two-year period and examined the efficacy and residual effect of four commercial insecticides including lambda-cyhalothrin, acephate, imidacloprid, and sulfoxaflor. The effectiveness and residual effects of these insecticides were determined by application on cotton field plots on four different dates during each season using three different concentrations. Four groups of cotton leaves were randomly pulled from each treated plot and control 0-2-4-7-, and 9-days post treatment (DPT) and exposed to a lab colony of TPB adults. One extra leaf sample/ plot/ spray /DPT interval (0-2-4-7-9-11) during 2016 was randomly collected from the high concentration plots and sent to Mississippi State for residual analysis. Mortality of TPB adults was greatest for those placed on leaves sprayed with the organophosphate insecticide with mortalities of 81.7% and 63.3% 1-day after exposure (DAE) on leaves 0-DPT with the high concentration for 2016 and 2017, respectively, reaching 94.5% and 95.4% DAE each year. Mortality to all insecticides continued until 9 and 4-DPT for high and medium concentrations, respectively. However, organophosphate (39.4%) and pyrethroid (24.4%) exhibited higher mortality than sulfoxamine (10.6%) and the neonicotinoid (4.0%) 7-DAE on 9-DPT leaves with the high concentration. Based on our results using the current assay procedure, TPB adults were significantly more susceptible to contact than systemic insecticides.