Ultra High Performance Liquid Chromatography – Pesticide Residue Analysis (Final Report) The purpose of this proposal was to purchase a LC-MS-MS in order to facilitate ongoing CRDF funded research requiring the analysis of pesticide residues in citrus leaf tissue. Funding provided by CRDF paid for a portion of this equipment which was cost-shared by UF-IFAS. The LC-MS-MS was delivered at setup in the Rogers’ lab at the Citrus Research & Education Center. Despite lengthy delays in getting the equipment to function properly due to installation of faulty parts, the LC-MS-MS is functional and is being used to meet the goals of other CRDF funded research projects. During the course of our method development period, we split research samples being analyzed for independent verification with the research labs of Bayer, Syngenta and Valent. Such interaction with these companies help use refine and perfect our methods being used for pesticide residue analysis. To date, the LC-MS-MS has been used to quantify parent compounds and metabolites of imidacloprid, thiamethoxam and clothianidin in citrus nectar collected as part of CRDF funded projects. The goal of these nectar analyses is to support pesticide label changes needed to help protect young trees from becoming infected with HLB. Our results from this project have played an important role in a larger group effort which has resulted in changes in the Admire Pro label, for which a 24C SLN was granted to increase the annual rate of product applied from 0.5 lbs a.i. per acre to 1.0 lbs a.i. per acre, and Belay Insecticide which now has a bearing label permitting use for trees in the 5-9′ size class. This equipment will continue to be used in similar efforts and additional studies looking at maximizing the effectiveness of currently used pesticides for psyllid control.