Impact of Different Potato Psyllid Populations on Zebra Chip Disease Incidence, Severity, and Potato Yield

Abstract

Zebra chip (ZC) is an emerging and damaging potato disease that is causing millions of dollars in losses to the potato industry in the southwestern United States, Mexico, and Central America. ZC plant symptoms resemble those caused by potato purple top and psyllid yellows diseases. Tubers produced by ZC-infected potato plants exhibit internal necrosis that affects the entire tuber. Fried chips processed from ZC-infected tubers have a characteristic striped pattern of necrosis and are unmarketable. This potato disease has recently been associated with the potato psyllid ( Bactericera cockerelli Sulc). A field experiment was conducted in southern Texas, under controlled cage conditions, to document the impact of different geographic populations of potato psyllid on ZC incidence, severity, and potato yield. Nine different colonies of psyllids were used in the study. Results showed that potato plants exposed to potato psyllids developed typical ZC symptoms in raw tubers and fried chips. ZC incidence in potato plants ranged from 0 to 100%. Not all insects used in the study were infective and only six psyllid colonies induced ZC symptoms in potatoes. No ZC symptoms were observed in psyllid-free control plots. Results indicated that ZC symptom severity in fried chips was correlated with ZC severity in raw tubers and with tuber weight. The impact of potato psyllid on potato yield and processing quality was highly significant. The number of commercially acceptable tubers per plant was significantly reduced and up to 93% potato yield loss occurred when potato plants were exposed to psyllids. Tubers from ZC-infected plants produced unmarketable potato chips.