Evaluation of the rainfastness of selected insecticides in cotton

Rainfastness of insecticides is an understudied aspect of agricultural research. Little is known about the residual of commonly used products for key pests of cotton, as well as their residual after a rainfall event. This project was designed to evaluate the impact of rainfall on the performance of commonly used insecticides for tobacco thrips, Frankliniella fusca (Hinds); tarnished plant bug, Lygus lineolaris (Palisot de Beauvois); and bollworm, Helicoverpa zea (Boddie), management in cotton. Laboratory and field experiments suggest that rainfall occurring within 16 hours after application had a negative impact on the performance of most insecticides. Chemical analyses of leaf tissue using a mass spectrometer confirmed what was observed with field and laboratory experiments. Although direct comparisons between insecticides cannot be made, results from this study suggest that spinosyns and insect growth regulators appeared to have the longest residual after a rainfall event