Submitted to: Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: July 31, 2006
Publication Date: August 15, 2006
Citation: Munyaneza, J.E., Crosslin, J., Jensen, A.S., Hamm, P.B., Schreiber, M.E. 2006. Beet leafhopper and potato purple top disease: 2005 season recap and new research directions. 45th Annual Proceedings Washington State Potato Conference. 2006: 107-118 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 in their fields. This outbreak caused significant yield losses and a reduction in tuber quality. A team of researchers from USDA-ARS Wapato and Prosser, WA; USDA-ARS Beltsville, MD; Oregon State University, Hermiston, OR; Washington State Potato Commission, Moses Lake, WA; and Agriculture Development Group, Inc., Eltopia, WA, investigated the disease causal agent(s) identification, insect(s) vectoring the disease, disease epidemiology, and disease management. It was found that this potato disease is caused by the beet leafhopper-transmitted virescence agent (BLTVA) phytoplasma and its major vector is the beet leafhopper. There are indications that some potato cultivars are more susceptible to BLTVA than others. 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 and plant hosts of BLTVA.
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), also known as the Columbia Basin potato purple top phytoplasma. The beet leafhopper is the major vector of the purple top pathogen in this region. At least three generations of the beet leafhopper are produced in the Columbia Basin and leafhoppers overwinter 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. Observations indicate that potato infection seems to take place early in the season. Weeds immediately surrounding fields play an important role in the beet leafhopper dispersal, hosting BLTVA, and in the epidemiology of the disease. 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.