Objective 1: Quantify the effect of citrus antimicrobials on vector fitness. We expect to observe reduced longevity, reduced fecundity, and longer development times among ACP exposed to antimicrobial treatments as compared with unexposed ACP. We previously reported (March 2019) on the effect of dietary antibiotic treatments on ACP survival (Obj. 1.1). During the past quarter, we evaluated the fecundity and fertility of ACP exposed to antibiotic treatments. The reproductive output of D. citri exposed to oxytetracycline or streptomycin treated plants was evaluated in a greenhouse assay. Five-month-old Citrus plants reared in an insect free greenhouse without exposure to insecticide received foliar applications of streptomycin (FireWall 50WP (Agrosource), or oxytetracycline (Agrosource,) or 1.0 mg ml-1 imidacloprid (Bayer CropScience LP), and water for a control. Females were allowed to oviposit on citrus plants with new growth (flush) over a 25-d period. Total eggs laid (fecundity) were counted under a stereoscope each 5-d period, then transferred to newly treated plants with flush to encourage oviposition. To determine if compounds containing oxytetracycline or streptomycin had an effect on the number of hatched eggs (fertility), plants were maintained as previously described for 6-d after adult removal. The total number of nymphs on plants were counted every 3-d under a stereoscope and recorded. This experiment is currently wrapping up and data analysis is underway. Objective 2. Determine the effect of antimicrobials on Las transmission. We expect that ACP feeding on antibiotic treated infected citrus plants will be less likely to transmit Las. We initiated field experiments to evaluate the hypothesis that ACP will be less capable of transmitting Las after feeding on antimicrobials, because trees treated with antimicrobials are more likely to have lower Las titers for acquisition (Objective 2.2). An experiment was initiated in mature, infected citrus trees located in a research at the CREC to determine whether field applications of foliar antimicrobials are also capable of suppressing acquisition of Las. Trees will be received an initial treatment with streptomycin, oxytetracycline, or receive no antimicrobial treatment. Ten insects from uninfected laboratory cultures were caged on young leaf growth (flush) of antimicrobial-treated or untreated infected trees using mesh bags for oviposition. Treatment were be replicated 10 times on individual trees. Survival of females is be monitored for two weeks. Females will be collected at the end of this quarter (late June) and preserved in 80% ethanol at -20°C for subsequent analysis and CLas detection. Egg clutches will remain on trees enclosed in mesh sleeves. After the nymphs reach the adult stage (approximately 15 days), adult psyllids and three leaves exposed to the psyllids will be collected for analysis.