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Oral: The Impact of Vector-Borne Bacteria Pathogen on Associated Hosts


The impact of Time of Infection on Zebra Chip Symptom Development.
C. RUSH (1), F. Workneh (1), L. Paetzold (1), A. Rashed (2) (1) Texas A&M AgriLife Research, U.S.A.; (2) University of Idaho, U.S.A.

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Zebra Chip (ZC) is an important disease impacting potato production in the Central and Western US. The disease is caused by the bacterium ‘Candidatus Liberibacter solanacearum’ (Lso), which is transmitted by the potato psyllid. Symptoms of ZC typically don’t appear until after flowering and this raised questions of when vector management should be initiated and how long it should continue. A field study was conducted in which plants were infested with bacteriliferous psyllids beginning one week after plant emergence and continuing until a week before harvest. Each week, infested plants were observed and initiation of symptoms and subsequent disease severity were recorded. At harvest, tubers were dug, rated for disease severity, tested for Lso and placed into cold storage. Later they were planted and emergence was recorded. With all infestation dates, it took approximately 23 days for first symptoms to appear and plants infested during the first five weeks after emergence exhibited the worst foliar and tuber symptoms. Plants infested three weeks before harvest typically showed no/few foliar symptoms but tuber symptoms were present and Lso detectable. Two weeks before harvest there were no foliar or tuber symptoms but Lso could be detected in a low percentage of tubers. Lso was not detected in tubers infested one week before harvest but a high percentage of these failed to grow after planting. The significance of late season infestations will be discussed.