Evaluation of Two Reduced-Risk Foliar Insecticides in Managing Neonicotinoid-Resistant Tobacco Thrips in Cotton

INTRODUCTION: Erosion of tobacco thrips (Frankliniella fuscaHinds) control in seedling cotton due to resistance to neonicotinoid seed treatments prompted an examination of a post-emergent foliar insecticide sprays with different modes of action.

METHODS: A two-year cotton field trial compared the efficacy of two, reduced-risk foliar insecticides (spinetoram, IRAC group 5, and cyantraniliprole, IRAC group 28), applied at the emergence of the first true leaf, with that of existing seed treatments (thiamethoxam, imidacloprid, both IRAC group 4A) and the most commonly-used foliar insecticide (acephate, IRAC group 1B). The F. fusca population at the trial location was 23- and 5- fold resistant to thiamentoxam and imidacloprid, respectively. Thrips damage rating, egg and larval numbers, and seedling growth were evaluated at multiple time points in the trial.

RESULTS: Relative to the untreated plants, all treatments reduced egg and larval numbers and damage rating. Treated plants grew taller and were heavier than their untreated counterparts. Both spinetoram and cyantraniliprole were comparable to or better than the seed treatments and acephate at reducing thrips damage and promoting plant vigor. Collectively, these results show that reduced-risk foliar insecticide sprays have utility in managing thrips in cotton, and could play an important role in managing these insects as resistance issues with current insecticides continue to worsen.