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United States Department of Agriculture

Agricultural Research Service

Title: Update on the Potato Purple Top Disease in the Columbia Basin

Authors
item Munyaneza, Joseph
item Crosslin, James
item Jensen, Andrew - WA ST POTATO COMM
item Hamm, P - OR ST UNIV, HERMISTON
item Thomas, P - USDA-ARS, RETIRED
item Pappu, H - WA ST UNIV, PULLMAN
item Schreiber, A - AGRIC DEVELOPMNT GRP

Submitted to: Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: April 7, 2005
Publication Date: July 29, 2005
Repository URL: http://hdl.handle.net/10113/30195
Citation: Munyaneza, J.E., Crosslin, J., Jensen, A.S., Hamm, P.B., Thomas, P.E., Pappu, H., Schreiber, A. 2005. Update on the potato purple top disease in the Columbia Basin. Proceedings of the 44th Annual Washington State Potato Conference. pp. 57-70.

Interpretive Summary: An epidemic of purple top disease of potato occurred in the Columbia Basin of Washington and Oregon in 2002 growing season and caused significant yield losses to potato fields; there were also indications of reduced tuber quality resulting from diseased plants. The disease was also observed in 2003 and 2004 growing seasons, especially in potatoes that were not treated with insecticides, including organic potato fields. A multi-disciplinary team funded by Oregon and Washington State Potato Commissions and mainly made of entomologists and plant pathologists from USDA-ARS, universities, and potato industry in the area, 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. It was found that the potato purple top disease in the Columbia Basin is caused by the beet leafhopper transmitted virescence agent (BLTVA) phytoplasma. The beet leafhopper was found to be the principal carrier of BLTVA, and is the likely vector of the potato purple top phytoplasma in this region. Leafhoppers seem to invade the Columbia Basin potato fields around mid-May to mid-June. Late planted potatoes seem to be more vulnerable to the disease. Foliar insecticide applications are effective in controlling the leafhoppers but timing is crucial to reduce the number insecticide applications and to avoid flaring aphids and mites. 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 purple top 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; there were also indications of reduced tuber quality resulting from diseased plants. Symptoms in affected potato plants include a rolling upward of the top leaves with reddish or purplish discoloration, moderate proliferation of buds, shortened internodes, swollen nodes, aerial tubers, and early plant decline. These symptoms resemble very much those of purple top caused by psyllid damage or phytoplasma infection, and in some cases to those caused by potato leafroll virus (PLRV). Early investigation of the cause(s) of the disease indicated that leafhopper transmitted phytoplasmas may have played a significant role in this disease epidemic. 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. Results indicated that the potato purple top disease in the Columbia Basin is caused by the beet leafhopper transmitted virescence agent (BLTVA) phytoplasma and not aster yellows phytoplasma. The beet leafhopper is the likely vector of the potato purple top phytoplasma in this region. Weeds immediately surrounding fields play an important role in the dispersal of the beet leafhopper and epidemiology of the potato purple top disease. Leafhoppers seem to invade the Columbia Basin potato fields around mid-May to mid-June. Late planted potatoes seem to be more vulnerable to the disease. Foliar insecticide applications are effective in controlling the leafhoppers but timing is crucial to reduce the number insecticide applications and to avoid flaring aphids and mites.

Last Modified: 11/27/2014
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