Conservation Biological Control of Bemisia Argentifolii in Cotton: Selectivity of Novel Insecticides Towards Arthropod Predators in Field Studies

Abstract

Arizona has a successful integrated pest management plan for arthropod pests of cotton including two key pests, Bemisia argentifolii and Lygus hesperus. Central to this plan is conservation of natural enemies through threshold-based, effective use of selective insecticides. Field studies in 2017 and 2018 were designed to test the selectivity of the insecticides cyantraniliprole, flupyradifurone, pyrifluquinazon and sulfoxaflor on the cotton arthropod community (27 taxa measured), which includes the key generalist predator species: Collops spp., Orius tristicolor, Geocoris punctipes, Misumenops celer, Drapetis nr. divergens and Chrysoperla carnea. Compared with an untreated control and in contrast to acephate-treated positive controls, predator densities were rarely impacted and the overall arthropod community was conserved by all insecticides. Occasional significant reductions in predator abundances were likely associated with lower prey availability after insecticide sprays rather than direct toxic effects. The percentage of time that predator to prey ratios were above levels favoring functioning biological control were either numerically or significantly higher or not significantly different from the untreated check for these insecticides. The cotton food web populated by generalist predators is resilient and flexible enough to accommodate temporary reductions in abundance of some species, periods of low prey densities, or other constraints on individual predator species function. Our study demonstrates that the insecticides tested are selective and compatible with sustainable pest management in the Arizona cotton system, representing new options for insect pest control that conserve natural enemies and support biological control through generally favorable changes to predator to prey ratios.