Submitted to: Potato Country USA
Publication Type: Popular publication
Publication Acceptance Date: 12/10/2006
Publication Date: 12/15/2006
Citation: Munyaneza, J.E. 2006. Potato Purple Top Disease and Beet Leafhoppers in the Columbia Basin. Potato Country USA 22:28-29. Interpretive Summary: During the 2002 growing season and ensuing years, Columbia Basin potato growers in Washington and Oregon witnessed a serious outbreak of potato purple top disease that caused significant yield losses and a reduction in tuber quality. A team of researchers from the Pacific Northwest, including USDA-ARS Wapato and Prosser, WA, investigated the causal agent and vectors of the disease. It was found that this potato disease is caused by the beet leafhopper-transmitted virescence agent phytoplasma and its vector is the beet leafhopper. Information from the present study will help growers in the Columbia Basin make effective and environmentally sound management decisions to reduce losses to potatoes due to this disease by monitoring and controlling beet leafhoppers.
Technical Abstract: A recent epidemic of purple top disease of potato occurred in the Columbia Basin of Washington and Oregon and caused significant yield losses to potato fields and reduction in tuber quality. Symptoms in affected potato plants include an upward rolling of the top leaves with reddish or purplish discoloration, moderate proliferation of buds, shortened internodes, swollen nodes, aerial tubers, and early plant decline. A multi-disciplinary team mainly made of entomologists and plant pathologists was formed to investigate various aspects of the problem, including disease causal agent(s) identification, insect(s) vectoring the disease, disease epidemiology, and disease management. Using PCR technique, it was determined that the potato purple top disease in the Columbia Basin is caused by the beet leafhopper-transmitted virescence agent (BLTVA). The beet leafhopper is the major vector of the purple top pathogen in this region. This leafhopper overwinters locally on weeds in the vicinity of potato fields throughout this potato producing region. Leafhoppers seem to invade the Basin potato fields around mid-May to mid-June and are present in potatoes throughout the growing season. About 15% of beet leafhoppers overwintering near potato fields in the Basin carry the BLTVA phytoplasma. There are indications that some potato cultivars are more susceptible to BLTVA than others, at least under laboratory conditions. In addition, preliminary results indicate that the potato yield and tuber quality are affected by purple top disease. Some insecticides, when timely and appropriately applied, appear to effectively manage the beet leafhopper and the potato purple top disease.