Managing beet leafhopper and potato purple top disease in the Columbia Basin

Since 2002, Columbia Basin potato growers in Oregon and Washington have experienced serious outbreaks of potato purple top disease that caused significant yield losses and a reduction in tuber quality. The beet leafhopper-transmitted virescence agent (BLTVA) phytoplasma is the causal agent of the disease and the pathogen is transmitted by the beet leafhopper (BLH), Circulifer tenellus L. The objective of this two-year study was to determine the relationship between BLH density and the likelihood of BLTVA transmission and purple top development. The study was conducted in a screen house at the Oregon State University Hermiston Agricultural Research and Extension Center, Hermiston, OR. Data suggests that younger plants appear more susceptible to BLTVA than mature ones. When BLH were released at the vegetative growth stage, BLTVA incidence increased steadily. First symptoms appeared between 2-3 weeks after insect release (11%). There was no difference in BLTVA incidence between the low (1 BLH per plant) and high (5 BLH per plant) BLH densities at harvest. Information from this study will help growers develop strategies to better manage purple top disease in Columbia Basin potatoes. Currently, BLH are basically controlled by chemical means.