Evaluating Efficacy and Chemical Concentrations of Commonly Used Insecticides Targeting Tarnished Plant Bug in Mid-South Cotton

Abstract

Studies were conducted from 2017 to 2021 at nine locations across Arkansas, Louisiana, Mississippi, and Tennessee to evaluate efficacy, residual control, and effective chemical concentrations of commonly used insecticides targeting tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), nymphs in Mid-South cotton. Foliar applications of imidacloprid, flonicamid, thiamethoxam, oxamyl, dicrotophos, acephate, novaluron, and sulfoxaflor were applied at locally recommended rates. Plots were sampled for nymphs at 4, 7, and 10 d after treatments (DAT), and leaves were analyzed for concentration of active ingredients from plots located in one site in 2021 at 4, 7, 10, and 14 DAT. Across all sampling dates, insecticide treatments reduced nymph infestations compared to untreated control, except for imidacloprid at 10 DAT. All insecticide treatments resulted in higher lint yields compared to untreated control. Overall, sulfoxaflor, novaluron, and acephate offered the best control of nymphs and provided the greatest yield protection among treatments. Moderate control was achieved with thiamethoxam, oxamyl, and dicrotophos. Imidacloprid and flonicamid resulted in less control. Concentrations of flonicamid, thiamethoxam, dicrotophos, acephate, and novaluron persisted up to 14 DAT in leaves. Imidacloprid and oxamyl were not detected at 7, 10, or 14 DAT, and sulfoxaflor was not detected at 14 DAT in leaves. In these studies, control of tarnished plant bug nymphs never exceeded 75% regardless of insecticide or sampling date. The moderate efficacy and short residual control shown in these studies explain why multiple insecticide applications within short intervals are needed to manage heavy tarnished plant bug populations