DISEASES OF SOYBEAN - WHITE MOLD

To verify that white mold is the disease that is causing the wilting, check for the characteristic white mycelium (mass of fungal threads) that is produced on the surface of the plant (see black arrow in photo). Later in the growing season, the fungus forms sclerotia both on and within diseased/dead plant parts, including stems (see white arrows in photo) and pods. Sclerotia drop to the soil where they are buried during disking, plowing or other soil activities.

Modification of cultural practices is the most effective means of controlling white mold. When planning rotations, avoid growing soybeans after snap beans or sunflowers, as both of these crops are very susceptible to white mold. When planting soybeans, use wider row spacings. White mold tends to be most severe in drilled soybeans where high plant densities promote high humidity. High humidity favors infection and disease development. Variety selection may also help in disease management. Some white mold resistant varieties are available. Finally, some growers have had some success in controlling white mold using certain herbicides. This management strategy is extremely tricky because timing of application is critical in disrupting the pathogen’s reproductive cycle. In addition, using inappropriate rates of a herbicide can lead to severe yield loss due to toxicity to the soybean crop.