Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/15/2014
Publication Date: 5/8/2014
Citation: Rashed, A., Wallis, C.M., Workneh, F., Paetzold, L., Rush, C.M. 2014. Potato psyllid vector density and zebra chip disease. In: Workneh F, Rush CM, eds., Proc 13th Annual SCRI Zebra Chip Reporting Session. Fredric Printing, Aurora, CO. pp. 136-140. Interpretive Summary: Zebra chip disease (ZC), caused by the bacterium ‘Candidatus Liberibacter solanacearum’ (Lso) and vectored by the potato psyllid Bactericera cockerelli, is an emerging threat to North American potato production. The current best ZC management practice is to spray insecticides for psyllid vectors. However, relationships between psyllid numbers per plant, Lso titers, ZC tuber symptoms, and associated biochemical shifts are poorly understood. This study inoculated two different varieties of potato plants with five, fifteen, or thirty Lso-positive psyllids and observed resultant Lso titers, ZC symptoms, and tuber biochemical changes. Greater numbers of psyllids resulted in greater tuber Lso titers, ZC symptoms, and phenolic compound levels regardless of potato cultivar. These results help to determine how many psyllids are potentially allowable before insecticidal sprays are warranted for ZC control.
Technical Abstract: Zebra chip disease (ZC), which is caused by ‘Candidatus Liberibacter solanacearum’ (Lso) and vectored by potato psyllids Bactericera cockerelli, is a continuing threat to the North American potato industry. Current management entails frequent insecticide sprays for the vectors as thresholds for spraying have not yet been established. Therefore, this study was conducted to evaluate whether different numbers of Lso-positive psyllids feeding on potato plants could affect subsequent Lso titers in potato tubers, ZC tuber symptom severity, and ZC-associated tuber biochemistry. Red La Soda and Russet Norkotah tubers were planted in the field and inoculated using five, ten, or thirty Lso-positive potato psyllids. Fifteen amino acids, four sugars, and seventeen phenolics were quantified following Lso infection. In both cultivars, when greater numbers of psyllids were used for inoculations then greater Lso titers and more severe ZC symptoms occurred. Many amino acids, carbohydrates, or phenolics were greater in tubers from plants that were inoculated using 30 psyllids than those inoculated using five psyllids or plants left non-infected as controls, and some cultivar effects were observed. The presence of greater than five psyllids may have resulted in undesirable increases in ZC tuber symptom progression.