SD47: Monitoring insecticide resistance in western flower thrips (Frankliniella occidentalis) populations in fruiting vegetable production systems

The western flower thrips (Frankliniella occidentalis (Pergande), “WFT”) is a key pest of fruiting vegetables, causing major crop losses through direct feeding and oviposition, and indirect damage by vectoring tomato spotted wilt virus (TSWV). Due to heavy reliance on a limited number of effective insecticides as a primary control strategy, the continued development of insecticide resistance in WFT poses a significant management challenge. Notably, WFT has developed resistance to spinetoram, one of the most widely used and effective insecticides for WFT management in tomato and peppers. Spinetoram resistance in WFT is associated with a target-site mutation (G275E) in the nicotinic acetylcholine receptor α6 subunit, which disrupts the insecticide binding and efficacy. Understanding the prevalence and spatial distribution of resistant allele frequencies in WFT populations across agroecosystems is critical for developing sustainable management programs. In this study, we collected WFT populations from regions representing low, medium and high resistance risk. Using a validated allele-specific qPCR assay, we monitored the frequency of the G275E resistance allele from overwintering hosts (strawberry, wheat, grasses) and vegetable crops (tomato, pepper and cucumbers) across North Carolina. Our results indicate that the majority of the WFT populations we sampled carry the resistance mutation, aligning with the historical spinetoram use pattern in these areas. These findings underscore the importance of continued resistance monitoring to inform evidence-based decisions on insecticide rotation among different modes of action.