Disrupting transmission of Candidatus Liberbacter asiaticus with antimicrobial therapy

1. Please state project objectives and what work was done this quarter to address them:Objectives1. Quantify the effect of citrus antimicrobials on vector fitness.  2. Determine the effect of antimicrobials on Las transmission.  3. Determine the effect of antimicrobials on plant response and associated ACP behavior.   The goal of this proposal was to determine whether antimicrobial treatments interfere with Asian citrus psyllid (ACP) populations and their capacity to transmit Candidatus Liberibacter asiaticus (Las), the causal agent of citrus greening (HLB). The premise of this technique is to kill Las with application of registered antimicrobials, streptomycin (Firewall) and oxytetracyline (Fireline) to the tree beyond the pathogen’s capacity to survive. These data suggest that antimicrobials used for CLas management, particularly oxytetracycline, elicit lethal and sublethal effects in D. citri. We determined that antibiotic use has a negative impact on ACP, therefore there is utility of these applications for ACP management in addition to any effects on Las in trees. ACP feeding on bactericide treated trees could be less capable of transmitting CLas to healthy trees. This can be due to 1) trees treated with bactericides are more likely to have lower CLas titers for acquisition and 2) CLas in infected will be reduced or eliminated when ACP feeds on bactericides, and 3) trees treated with bactericides prior to ACP will be protected from CLas inoculation. Given the limited efficacy of antimicrobial treatments to eliminate CLas completely in infected trees, it appears that their greatest benefit may due to their negative effects on the ACP vector and CLas transmission.  2. Please state what work is anticipated for next quarter: The project is complete. The final work will consist of completing data analysis and submitting manuscripts for publication. 3. Please state budget status (underspend or overspend, and why): Our budget was slightly underspent due to orders for materials to extract DNa not received by the project end date.