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Posted 25 June 2007. PMN Crop News.

Potato Wart Eyed as Risk to Potato Production

American Phytopathological Society.

St. Paul, Minnesota (June 18, 2007)--While many may be familiar with potato late blight, the plant disease responsible for widespread potato shortages, the lesser known potato wart has the potential to be as devastating to economies that depend on potato production, say plant pathologists with The American Phytopathological Society (APS).


According to Gary Franc, plant pathologist with the College of Agriculture, Plant Sciences Department at the University of Wyoming, Laramie, WY, potato wart is a serious disease of cultivated potato that has been detected worldwide. Potato wart is caused by the fungus Synchytrium endobioticum, which is considered to be the most important worldwide quarantine plant pathogen of potato. While not harmful to humans, the disease causes unsightly growths that initially appear white, and then turn brown or black as they decay, rendering the potato tuber unrecognizable and inedible.

There is a zero tolerance for the fungus that causes potato wart. As a result, this disease has been placed on the USDA’s “Select Agent List” of plant pathogens deemed to pose a severe threat to plant health or to plant products. Although direct losses from potato wart may be insignificant when first detected, indirect economic losses resulting from zero-tolerance regulations for potato wart can be devastating to growers. Indirect economic losses become especially evident in potato production areas that are subject to quarantine measures, as well as when the movement of commercial potatoes is restricted.

Spores released from infected plants can make soil unsuitable for potato production for decades. The long-term survival of fungal spores and the lack of suitable chemical controls for potato wart suppression make this disease especially problematic for any type of cultivated potato production, including small garden plots and subsistence farming to extensive land areas economically dependent on commercial production of potatoes for consumption or for potato seed production.

“Potato wart is much easier to prevent than it is to control,” Franc said. “It is highly critical that we prevent the introduction of the potato wart pathogen to production areas, and, where it is already introduced, to limit its spread,” he said.

“While regulatory action is important in potato wart management, it is essential that research efforts continue with the goal of developing and improving reliable and integrated disease suppression methods to directly deal with this disease,” said Franc.

More information on potato wart is available on the APS website at This article is the first in a series on plant diseases included on USDA's Select Agent List.

APS is a non-profit, professional scientific organization. The research of the organization’s 5,000 worldwide members advances the understanding of the science of plant pathology and its application to plant health.

Amy Steigman
American Phytopathological Society