D3066: What drives a thrips to thrive? investigating abiotic factors influencing Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae) persistence in the field

Schinus terebinthifolia Raddi (Brazilian peppertree) is an invasive shrub that grows aggressively, often forming dense monotypic stands that can outshade and outcompete native vegetation for resources. As one of Florida’s worst upland invasive plant species, it has been the target of biological control programs for many years. The classical biocontrol agent, Pseudophilothrips ichini (Hood) (a thrips), was approved for release in Florida in 2019 and over six million thrips have been released to date with varying levels of establishment success. In this study, we released 7,000 thrips at sixteen different sites (112,000 total) and monitored the site-level abiotic factors over 22 months to see which had the greatest influence on P. ichini persistence. Our results indicate that habitat type, soil moisture levels, and mean temperature significantly influence thrips abundance and persistence. Model predictions suggested that thrips were 7.2 times more likely to be found at upland sites than at wetland sites. We also observed population increases in the winter and decreases in the summer, which could indicate either the movement of thrips into more protective areas of the tree canopy that are inaccessible for surveys or seasonal dormancy. These results suggest that release efforts should be concentrated on upland areas and surveying for establishment should be conducted in the winter for true estimates of thrips persistence. Our results will significantly improve current release and monitoring protocols for those involved in this biocontrol program.