Development of Insecticide Resistance in Field Populations of Onion Thrips, Thrips tabaci (Thysanoptera: Thripidae)

Simple Summary Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), are one of the most economically significant insect pests in onions, garlic, chives, leeks, and other Allium species. The resistance to different insecticides in thrips is a reality, but there is scarce literature available on this fact. The current study evaluates the status of insecticide resistance in eight geographically distinct field populations in comparison with a susceptible laboratory population of onion thrips in Pakistan using concentration-response bioassays on eight commonly used insecticides. Overall, all tested populations were found to have different levels of resistance varying with population location and chemicals. There were high levels of resistance noted in deltamethrin, mostly in populations from South Punjab, Pakistan. Among the insecticides, spinosyns remain effective and may provide better control of thrips in onion fields. The present study evaluated insecticide resistance in field populations of onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), collected from eight different onion-growing regions of Punjab, Pakistan. These field-collected populations were assessed for resistance development against eight commonly used active ingredients including deltamethrin, lambda-cyhalothrin, imidacloprid, acetamiprid, spinosad, spinetoram, cypermethrin, and abamectin. In leaf dip bioassays, T. tabaci adults showed varied levels of resistance towards different insecticides. Moderate or high levels of resistance to deltamethrin (58-86 fold), lambda-cyhalothrin (20-63 fold), and cypermethrin (22-54 fold) were observed in T. tabaci field populations. There were very low to moderate resistance levels to imidacloprid (10-38 fold), acetamiprid (5-29 fold), and abamectin (10-30 fold). The lowest levels of resistance were detected in thrips exposed to spinosad (3-13 fold) and spinetoram (3-8 fold). Insecticide resistance levels varied among populations collected from various geographic locations, but all populations exhibited elevated levels of resistance to deltamethrin. Thrips tabaci populations with higher resistance levels were most commonly found from the southern part of Punjab, Pakistan. Our findings revealed that spinosyns could be used as alternatives to conventional insecticides for the successful management of T. tabaci in onion fields.