"Candidatus Liberibacter solanacearum" associated with Bactericera maculipennis (Hemiptera: Triozidae): Evidence for plant-mediated horizontal transmission of Liberibacter between psyllid species

Bactericera maculipennis (Hemiptera: Triozidae) is a psyllid native to the western United States which commonly uses the invasive perennial weed, field bindweed (Convolvulus arvensis, Solanales: Convolvulaceae) as a naturalized host.  The potato psyllid, B. cockerelli, also uses field bindweed as a seasonal host when potato (Solanales: Solanaceae) or other solanaceous crops are not available.  B. cockerelli is an important agricultural pest largely because it is a vector of "Candidatus Liberibacter solanacearum," the pathogen associated with zebra chip disease of potato.  Although plants within the Convolvulaceae are not suitable hosts for Liberibacter, plant-mediated horizontal transmission of Liberibacter occurs among B. cockerelli on field bindweed, but only when infected and uninfected psyllids are concurrently present on the plants.  The overall goal of our study was to determine whether interspecific transmission of Liberibacter can or has occurred between B. cockerelli and B. maculipennis.  Results of laboratory assays showed that plant-mediated transmission between B. maculipennis and B. cockerelli can occur on bindweed plants. “Ca. Liberibacter solanacearum” infected wild populations of B. maculipennis in Washington and Idaho at rates from 7% to 60%. We found no evidence that Liberibacter is not transmitted from mother to offspring. To conclude, our study demonstrates that plant-mediated transmission between psyllid species can occur and that B. maculipennis could be a reservoir for Liberibacter in the Pacific Northwest.