Interactions Among Bactericera Cockerelli, Host Plants, and Liberibacter Solanacearum

The potato psyllid, Bactericera cockerelli, is a pest of Solanaceous crops and the vector of “Candidatus Liberibacter solanacearum”, the causal agent of zebra chip disease of potato. The disease was first described in the 1990s, but the pathogen and vector were not identified until 2007. Therefore, little is known about interactions among Liberibacter, psyllids, and host plants. Convolvulaceae including sweet potato are hosts for potato psyllids. Studies on the potential role of Convolvulaceous plants in Liberibacter epidemiology are lacking, but preliminary results suggest these plants do not support the pathogen. Two separate studies were conducted to determine whether Liberibacter transmission occurs among psyllids on sweet potato. First, infected and non-infected psyllids were confined to whole plants. The previously non-infected psyllids became infected after one week. The second study confined infected psyllids on single leaves and non-infected psyllids on three leaves above each treatment leaf. The previously non-infected psyllids became infected after one week presumably due to Liberibacter movement through the phloem to the target leaves. A dye injected into the treatment leaf accumulated in target leaves, supporting this interpretation. Liberibacter was not detected in study plants, even after prolonged incubation periods. Results suggest that sweet potato may operate as a source for horizontal disease transmission among psyllids. Alternatively, sweet potato may be an asymptomatic host for Liberibacter, but conventional PCR fails to detect the pathogen from this plant. Regardless, results indicate that certain Convolvulaceous plants may be important sources for Liberibacter-infected psyllids migrating in potato fields.