Charcoal Rot on Soybeans

This article was originally published on July 30, 2012 and expired on August 6, 2012. It is provided here for archival purposes and may contain dated information.

The drought of 2012 will go down as one of the worst in history, and the impact of that drought will stretch well into harvest. Disease will undoubtedly be part of that drought package, and a specific bean disease is probably on its way. Conditions are favorable for the development of charcoal rot on soybeans.

Charcoal rot, just like so many of the other plant diseases, is a fungus. It is favored by hot, dry weather like that which we are currently experiencing in several locations throughout the county.

While slightly more prone to appear in southern Illinois, charcoal rot can appear in central Illinois when additional stress is applied to the crop. In 2012, that additional stress would be the occurrence of drought conditions that are hammering away at our soybeans.

The symptoms of the disease, what the disease causes to change in the plant, and the signs of the disease, visible parts of the disease causing fungus are both detectable toward profill. Plants will yellow toward the top, wilt, and often die.The tap root and stem of the plant will look very grey to silvery in color, and when the epidermal tissue around this area is pealed back, small black specks, fruiting bodies of the disease referred to as sclerotia, will be observed. Internal tissue may initially be reddish brown and then turn greyish black.

Charcoal rot overwinters in two ways. First, it can overwinter as small black fruiting bodies within the soil. Second, the fungus may overwinter within plant debris. A wide range of plants, including corn, can be attacked or can house this disease.

So what can be done if this rare disease does rear its head in our area? Very little can be done once the disease has appeared. However, options are available to manage this disease in years to come. First, wherever stress appear and can be managed, such as insect problems or fertility problems, they should be. Second, deep tillage of fields, where soil erosion is minor enough to allow it, can help to deter the disease by burying sclerotia and infected plant debris where they cannot cause problems.

Pull date: August 6, 2012