Interior sclerotia can be seen easily by splitting open diseased stems. Because the fungus eventually constricts the plant tissue, water and nutrients cannot move to upper plant parts, and as a result entire branches or plants may be killed. Sclerotia are special survival structures that can survive in the soil for five or more years. When spring arrives and moist conditions occur, brown, saucer-shaped structures form on stalks that grow from the sclerotia. Apothecia release fungal spores that may then infect a susceptible plant that is growing in the vicinity.
Several practices help control white mold.
Since the fungus thrives in abundant moisture, practices that favor drying of the plant tissues, such as wide spacing at planting, will help reduce the chance of infection. If the disease does occur, all diseased plant parts should be cleaned up and destroyed to prevent or reduce the number of sclerotia added to the soil. Because the sclerotia can survive for a number of years in the soil, rotation with a crop that is not susceptible to the disease is helpful, but will not eliminate the pathogen. Deep plowing of the soil will help to speed decomposition or breakdown of the sclerotia. Various broadleaf weeds, such as pigweed, velvet leaf, ragweed and Canada thistle, are susceptible to the disease.