|Potato zebra chip in the Pacific Northwest: Impact and probable psyllid source assessments.|
F. WORKNEH (1), M. Mirik (2), A. Rashed (1), P. B. Hamm (3), J. Ansley (2), C. M. Rush (1). (1) Texas AgriLife Research, Bushland, TX, U.S.A.; (2) Texas AgriLife Research, Vernon, TX, U.S.A.; (3) Oregon State University, Hermiston, OR, U.S.A.
Since its first detection in south Texas in 2000, potato zebra chip (ZC), caused by ‘<i>Candidatus</i> Liberibacter solanacearum’, which is vectored by the potato psyllid (<i>Bactericera cockerelli</i>), has spread into the central and southwestern US, causing substantial losses in production. In 2011, the disease was observed for the first time in the Pacific Northwest (PNW: ID, OR, and WA), triggering widespread concerns over its probable impact on the region, which accounts for the majority of potato production in the US. While the overall disease incidence across the region was low, harvested potatoes from some of the affected fields had up to 32% ZC incidence. Infra-red remote sensing of these fields, in which plants were classified as healthy or diseased, provided a significant correlation (<i>R</i><sup>2</sup> = 0.99, <i>P</i> = 0.002) with ZC incidence in harvested tubers. However, remote-sensing overestimated ZC incidence when compared to the incidence in tubers, probably because of the presence of aerial plant symptoms similar to ZC that were caused by other factors. The source of potato psyllids that were responsible for the 2011 ZC outbreak in the PNW is unknown. However, potato psyllids overwinter in the southwestern US (TX, NM, AZ, and CA) and may migrate north in the spring each year. Air-parcel trajectory analysis for the 2011 season implicated Arizona and California as probable sources, but ruled out Texas and New Mexico.<p><p>Keywords: Bacteria-Phytoplasma-Spiroplasma-Fastidious Prokaryote, Root-Tuber Crops, Potato