Impact of the potato psyllid, Bactericera cockerelli (Hemiptera: Triozidae), on potato yield and seed quality

Potato psyllids, Bactericera cockerelli (Hemiptera: Triozidae), can greatly impact potato production in the western United States through direct feeding, historically known as the disease psyllid yellows, and more recently as vectors of the pathogen, Candidatus Liberibacter solanacearum (CLs), which has been associated with the disease zebra chip. Our study compared these two psyllid-related diseases on two common potato cultivars (Atlantic and Ranger Russet) in 2009 and 2010. We used field cages of CLs-infective and CLs-free psyllids to examine the separate and combined effects of these two diseases on yield: zebra chip alone (short exposure of CLs-infective psyllids), psyllid yellows alone (long exposure of CLs-free psyllids), zebra chip and psyllid yellows (long exposure of CLs-infective psyllids) and a control (no psyllids). Plants were monitored for foliar and tuber symptoms and yield was measured. Tubers from the 2009 season were planted the following year to estimate seed quality. Yield loss was most severe in the two zebra chip treatments; the psyllid yellows treatment also caused a yield reduction relative to the control. The observed trends were similar between cultivars and years. For the seed trial, emergence rates were very low for any seed affected by zebra chip and results varied between cultivar; emergence rates and yield were similar between the control and the psyllid yellows treatments regardless of cultivar. This research will assist commercial and seed potato growers in making pest and disease management decisions and has helped to clarify the combined and separate effects of these two important potato psyllid-related diseases.