BIORATIONAL CONTROL METHODS FOR INSECT PESTS OF POTATO
Location: Fruit and Vegetable Insect Research
Title: Zebra chip progression: from inoculation of potato plants with liberibacter to development of disease symptoms in tubers
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 17, 2012
Publication Date: March 9, 2012
Citation: Buchman, J.L., Fisher, T.W., Sengoda, V.G., Munyaneza, J.E. 2012. Zebra chip progression: from inoculation of potato plants with liberibacter to development of disease symptoms in tubers. American Journal of Potato Research. 89:159-168.
Interpretive Summary: Zebra chip, a new and economically important disease of potato, is caused by a new species of the bacterium liberibacter vectored by the potato psyllid. Researchers at USDA-ARS Wapato, WA, determined when zebra chip symptoms developed in potato tubers following plant exposure to the bacterium. The zebra chip disease symptoms developed in tubers three weeks following plant exposure to liberibacter and tuber development stopped with the onset of disease symptoms, resulting in substantial yield loss and reduction in tuber quality. This information will assist potato producers to make harvest timing decisions that minimize damage caused by zebra chip.
Zebra chip (ZC), a new and serious disease of potatoes, has caused millions of dollars in losses to the potato industry in the United States, Mexico, Central America, and New Zealand. The disease has been associated with the bacterium “Candidatus Liberibacter solanacearum” transmitted to potato by the potato psyllid, Bactericera cockerelli (Šulc). The most characteristic symptoms of ZC develop in potato tubers and include collapsed stolons, browning of vascular tissue concomitant with necrotic flecking of internal tissues and streaking of the medullary ray tissues, all of which can affect the entire tuber. Upon tuber frying, these symptoms become more pronounced and potato chips or fries processed from ZC-affected tubers show very dark blotches, stripes, or streaks, rendering them commercially unacceptable. Field experiments were conducted to determine how rapidly ZC symptoms develop in potato tubers following plant exposure to liberibacter-infective potato psyllids and to assess how the disease affects the overall potato yield and tuber processing quality over time. Results indicated that ZC symptoms developed in potato tubers three weeks following plant exposure to psyllids. Tuber development ceased upon the onset of ZC symptoms, resulting in substantial yield loss. Levels of tuber solids decreased as soon as initial disease symptoms were observed. In contrast, reducing sugar levels in tubers increased dramatically upon the onset of ZC symptoms, significantly affecting potato processing quality. This information, in combination with effective psyllid monitoring and control, could assist potato producers make harvest timing decisions following infestations of potato psyllids in their fields to minimize damage caused by ZC.