First Report of Potato Psyllids, Bactericera cockerelli, Overwintering in the Pacific Northwest

Potato psyllids became a topic of interest at the end of the 2011 growing season in the Pacific Northwest when they were first documented to transmit ‘Candidatus Liberibacter solanacearum,’ the putative pathogen causing zebra chip disease in the region. Zebra Chip is characterized by above and below ground symptoms that cause significant yield loss. For many decades it has been unclear whether the potato psyllid migrates to states in the Pacific Northwest from large, well-documented infestation areas in California or Texas. Thus, we conducted a study in the spring of 2012 in the lower Columbia Basin (north east Oregon and south east Washington state), and in the fall, winter, and spring of 2012 in southwestern Idaho to determine if psyllids could be found overwintering. Potato psyllid was observed in November 2011 in southwestern Idaho and March 2012 in the lower Columbia Basin living on Solanum dulcamara L. (i.e., bittersweet nightshade), a perennial weed of wet habitats and riverbanks. Potato psyllids were collected and brought to the laboratory. Emerging adults from both locations (i.e., Columbia Basin and Idaho) were offered potato plants and they completed a second generation in approximately 15 days under similar environmental conditions. While overwinter survival of the potato psyllid in the Pacific Northwest is concerning for the potato industry, weather trends in the region were mild during the winter of 2012. It is unknown whether a colder or longer winter season would affect the overwintering biology we have observed. Observations through several coming winters are warranted.