Impacts of biological control agent, Pseudophilothrips ichini, on Brazilian peppertree

Brazilian peppertree, Schinus terebinthifolia Hood (Anacardiaceae), is an invasive weed found in coastal regions of California, Hawaii, Texas, and throughout peninsular Florida. Florida Exotic Pest Plant Council considers S. terebinthifolia a category I invasive plant because S. terebinthifolia displaces native plant species, causing alteration of native plant communities, ecological functions, and community structures. Management of S. terebinthifolia costs the state of Florida roughly $2.5 million annually and relies on mechanical and chemical control methods. These management methods prove challenging and biological control efforts have been advocated as a sustainable alternative. In June of 2019, Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae) was released in Florida after approval by the USDA. Lab studies showed >50% reduction in plant relative growth rate, but it is unclear how that will translate to the field. We began releasing P. ichini in two field plots, in Fort Pierce and Immokalee, FL, in July 2019, to determine the impact of P. ichini on S. terebinthifolia. Half of the trees are treated with a systemic insecticide to exclude P. ichini damage. Plant height, basal stem diameter, canopy width, number of actively growing tips, and number of berries are measured or counted for each tree to determine relative growth rate. No differences have been found between insecticide-treated and P. ichini-treated plants. However, as our methods continue to improve for promoting establishment of thrips in the field and as insect populations continue to increase, we expect to see a decrease in relative growth rates of P.ichini-treated S. terebinthifolia.