Foliar-applied insecticide treatments may be necessary to control thrips in cotton under severe infestations or when at-planting insecticide seed treatments do not provide satisfactory protection. Acephate has been the most commonly used foliar insecticide for many decades, but its performance in field trials has recently declined in Tennessee. Researchers have assayed the efficacy of selected insecticides on tobacco thrips populations across the Mid-South and Southeast cotton production regions. In 2020 and 2021, leaf-dip bioassays were done on populations of tobacco thrips collected from wild hosts or cotton in Tennessee, Arkansas, Mississippi, Louisiana, Texas, Alabama, North Carolina, and Virginia. Bioassays were also performed on a North Carolina susceptible laboratory population that has been kept in a colony since 2013. Insecticides used in the leaf-dip bioassays included acephate, spinetoram, dicrotophos, lambda-cyhalothrin, and imidacloprid. The results of these bioassays indicate that tobacco thrips have developed resistance to acephate; however, this resistance seems to be concentrated in areas of the upper Mid-South. Further investigation is needed to identify the mechanism of thrips resistance to acephate. Our assays would also predict poor performance of neonicotinoids (e.g., imidacloprid) and pyrethroid insecticides—something that would be expected given the known resistance of tobacco thrips to these classes of insecticides.
