Strawberry production in Florida has several challenges from native and invasive arthropods. The invasive chilli thrips, Scirtothrips dorsalis Hood infest strawberry transplants early in the season. Several conventional insecticides are part of a rotation program currently used to manage S. dorsalis. However, S. dorsalis resistance development remains a concern, despite the rotation program. Therefore, the objectives of this study were to determine: 1) the extent of resistance in early season and late season S. dorsalis to spinetoram, acetamiprid, cyantraniliprole, and bifenthrin and, 2) the LC50 and LC90 values of S. dorsalis to spinetoram. Sampling of S. dorsalis populations were conducted in ten strawberry fields, twice during the strawberry field season of 2019 – 2020. Early season populations were collected in November 2019 and late season populations were collected in February-March 2020. Field collected populations were reared on cotton plants separately in Petri Dishes for at least a couple of generations. A susceptible 2 y old laboratory S. dorsalis population was used to compare the efficacy of the various insecticides at their manufacturer label rates using a Potter spray tower. Results indicate that S. dorsalis mortality rates were ~30% higher in the early season S. dorsalis populations as compared to late season populations. Spinetoram was most effective amongst all the insecticides tested, followed by cyantraniliprole and acetamiprid. The calculated LC50 and LC90 of spinetoram for laboratory population was 0.026 ppm and 8.64 ppm respectively. In contrast, susceptibility to spinetoram varied greatly among the field populations with LC90 exceeding 200 ppm.
