Click on any
image for a more
detailed view

Significance

Sclerotinia diseases, caused by S. sclerotiorum and to a lesser extent S. minor and S. trifoliorum, affect a wide range of crops. Literature reports of crop losses range from negligible to 100%. Crops where average annual losses from Sclerotinia diseases are thought to exceed 1% include bean, eggplant, lettuce, peanut, potato, soybean, and sunflower. Many of the greatest losses occur in intensive cropping environments where irrigation and optimal nutrition create a lush, dense plant canopy that promotes disease development. White mold is a soilborne disease that can develop into a serious and persistent problem when it becomes established in a field.

Sclerotinia sclerotiorum is geographically cosmopolitan and has a broad ecological distribution, although it is most common in temperate regions. Originally it was thought to occur only in cool, moist areas, but it is now known to occur in semi-arid areas as well. Plants susceptible to this pathogen encompass 64 families, 225 genera, and 361 species. Important cultivated plants susceptible to S. sclerotiorum include legumes, sunflowers, canola, most vegetables (e.g. potato, tomato, lettuce, and crucifers), tobacco, many flowering bedding plants, and stone fruits. Corn, sorghum, wheat and other small grains are not susceptible to Sclerotinia spp.

In soybean, S. sclerotiorum causes Sclerotinia stem rot, or simply white mold. Common beans are also very susceptible to white mold. Three distinct diseases of sunflower are caused by S. sclerotiorum: wilt disease produced by a basal stem infection, and head rot and middle stalk rot, both developing from ascospore infections.

Sclerotinia minor is found less commonly than S. sclerotiorum. It causes white mold and watery soft rots of vegetables. On peanut crops, S. minor causes Sclerotinia blight, a serious disease affecting all plant parts. S. minor causes lettuce drop by infecting plant roots, although in some fields aerial infection by S. sclerotiorum ascospores may also contribute to the disease.

Sclerotinia trifoliorum infects forage legumes to cause a white mold crown and stem rot. It can be a serious problem on fall-planted alfalfa. In the U.S. it occurs primarily in the southeastern and eastern states.

RETURN TO TOP