The effects of potato psyllid vector density, movement behavior, and host choice on pathogen spread and zebra chip disease severity

Zebra chip (ZC) is a disease of potatoes which is associated with the vector-borne bacterial pathogen ‘Candidatus Liberibacter solanacearum’ (Lso). The pathogen is transmitted by the potato psyllid Bactericera cockerelli (Hemiptera: Triozidae). Zebra chip-affected fields are characterized by sporadic presence of symptomatic plants, which are more prevalent on field edges than in center fields. Moreover, anecdotal observation suggests that disease severity and prevalence varies among cultivars. A study was conducted to evaluate effects of Lso infection and the number of infective potato psyllids on ZC severity and biochemistry (phenolics, amino acids, and reducing sugars) in two potato cultivars. Russet Norkotah was more severely affected by Lso infection than Red La Soda. In both cultivars disease severity was positively associated with vector number. Psyllid preference for different potato cultivars (FL1867, Red La Soda, Russet Norkotah, as well as silver-leaf nightshade) was evaluated through multiple-choice assays and their movement frequency and behavior will be discussed in relation to host plant density.