Efficacy of insecticides for season-long control of thrips (Thysanoptera: Thripidae) in winter strawberries in Florida

Abstract

Flower thrips (primarily Frankliniella spp.) can be significant strawberry pests, and recently in Florida, Scirtothrips dorsalis Hood has become an established, early-season, foliar pest. Insecticides that were used for flower thrips management are now also used for S. dorsalis, resulting in the need to evaluate newer insecticides in order to diversify rotations and mitigate overuse of insecticides with the same mode-of-action. We evaluated 10 and 12 season-long insecticide programs in field plots in central Florida during the 2016–2017 and 2017–2018 winter strawberry seasons, respectively. We found that most programs reduced thrips populations and strawberry injury due to thrips feeding, while having limited effects on Orius spp., a primary thrips predator. An early season application of chlorantraniliprole + thiamethoxam, commonly used for other strawberry pests, reduced S. dorsalis populations and strawberry injury, although S. dorsalis populations were relatively low in both study years. When repeat applications of the same insecticide were made throughout the growing season, cyantraniliprole was nearly as effective as spinetoram against Frankliniella spp., while tolfenpyrad and sulfoxaflor did not perform as well. Flupyradifurone was as effective as acetamiprid when used as a follow-up application to spinetoram or cyantraniliprole. Programs including or entirely composed of OMRI-listed insecticides for organic production were not as effective as conventional insecticide programs, with only spinosad providing acceptable thrips control. In conclusion, spinetoram, acetamiprid and spinosad were confirmed to be effective against thrips and can be used as the backbone of rotation programs in conventional and organic strawberry production systems. Diamide insecticides were effective when used repeatedly and in rotation, while flupyradifurone and flonicamid may be used when follow-up applications are needed. Continued research is critical for fine-tuning insecticide programs, with a focus on testing against high S. dorsalis populations in early-planted strawberries and on developing effective sampling methods to optimize timing and reduce the number of applications.