Associations of the Potato Psyllid and "Candidatus Liberibacter solanacearum" in Idaho with the Noncrop Host Plants Bittersweet Nightshade and Field Bindweed.

Zebra chip disease (ZC) in potato (Solanum tuberosum L. [Polemoniales: Solanaceae]) can produce unmarketable tubers with striped necrotic patterns. ZC is associated with the bacterium "Candidatus Liberibacter solanacearum" (Lso), which is transmitted by the potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae). Potato psyllids are associated with numerous noncrop host plants, especially from the Solanaceae and Convolvulaceae; however, the contribution and importance of these hosts to ZC epidemiology in potato is poorly understood. To clarify seasonal phenologies on two such hosts, we sampled potato psyllids from bittersweet nightshade, Solanum dulcamara L. (Polemoniales: Solanaceae), and field bindweed, Convolvulus arvensis L. (Polemoniales: Convolvulaceae), over 2013-2017 and 2014-2016, respectively. Adult psyllids were sampled using yellow sticky traps, vacuum samples, and beat sheets. Each psyllid was tested for the presence of Lso by polymerase chain reaction. Psyllids often were abundant on bittersweet nightshade during May to November, with low numbers observed over each winter. Vacuum samples often captured more psyllids than other methods. Lso incidence was low except during 2016 when vacuum samples showed 23% incidence. Potato psyllids regularly overwinter on bittersweet nightshade in Idaho; however, differences in psyllid populations and Lso incidence from those found on potato suggest that this host plant may only partly contribute to infestations in potato. Observations of psyllids on field bindweed suggest only transient visits to this plant around potato harvest, with no evidence of overwintering and no Lso detected. Further work is needed to clarify how potato psyllid use of other noncrop hosts is related to their abundance in Idaho potato fields.