It has been copied here because of its importance so that the link is not broken. By Paula Flynn Extension plant pathologist Iowa State University White mold may affect more than 100 different plant species. Many vegetable and ornamental plants are susceptible to white mold. The lengthy list of plants that may be infected includes beans, broccoli, cabbage, cucumber, lettuce, melons, onions, peas, peppers, potatoes, pumpkins, squash, tomatoes, watermelons, chrysanthemums, dahlias, daisies, delphiniums, euonymus, forsythias, hollyhocks, irises, peonies, petunias, snapdragons, sunflowers, zinnias and many others. In Iowa, the primary plant host of concern is soybean.
Plants attacked by the fungus usually show a wet rot on the stem.
When humid conditions occur, a cottony white mold is formed on the stems. Clumps of the cottony mold form that eventually become hard black structures called sclerotia. Sclerotia vary in size, usually ranging from pinhead-size to the size of a pea. Many times the black sclerotia can be seen on the outside of the stems. However, sclerotia also may be found embedded throughout the infected tissues.