New Research Initiative Wages War on White Mold

White mold is a far cry from the innocuous, fuzzy, blue-green growth that colonizes stale bread. In fact, this disease-causing broadleaf pathogen is the culprit behind U.S. crop losses of $150 million annually.

Now, a consortium of federal and state university scientists has declared war on white mold, Sclerotinia sclerotiorum. Leading the charge, including 10 land grant universities and five crop commodity groups, is the Agricultural Research Service, the U.S. Department of Agriculture's chief scientific research agency.

Begun in June 2002, the ARS-led National Sclerotinia Initiative supports 20 different projects aimed at neutralizing white mold's economic threat to seven different crops: sunflower, soybean, canola, edible dry beans, chickpeas, lentils and dry peas.

White mold typically attacks the flowers and stalks of all the crops and the roots of sunflower, as well, causing rot or wilt. In dry beans, for example, such attacks cost growers more than $25 million annually in production losses and $6 million in fungicide expenses. A 1999 outbreak in North Dakota, Minnesota and Nebraska cost sunflower growers $100 million in losses.

Controlling white mold can be difficult for several reasons, including its wide host range, the hard casing (sclerotia) it forms to survive harsh conditions, and the absence of disease resistance in commercial cultivars. This is according to Larry Chandler, director of ARS' Red River Valley Agricultural Research Center, which administers the $960,000 (2002) effort from Fargo, N.D.

There, and at cooperating universities, scientists are setting the stage for integrated approaches to managing white mold through three research fronts: studies of its disease cycle and spread; development of plant germplasm with resistance traits that can be passed into elite cultivars; and chemical, cultural or biological control of the pathogen.

At Fargo, for example, ARS scientists, including Tom Gulya, Jerry Miller and Gerald Seiler are screening wild sunflower species and commercial hybrids from Europe and Argentina for resistance to "head rot." It's a Sclerotinia disease that diminishes sunflower seed and oil quality. The Fargo group plans on releasing three promising germplasms this spring to commercial seed companies.