COLUMBIA, Mo. — The heavy rainfall that followed the summer-long drought has brought sooty molds to Missouri cornfields, leaving many plants blackened with fungal growth, a University of Missouri plant disease specialist said.
"I had several people tell me that after the rains on the Labor Day weekend, entire corn fields turned black," said Laura Sweets, MU Extension plant pathologist with the Commercial Agriculture Program. "From the roads, the fields had a black cast or appearance. From a closer perspective, the leaves, stalks and husks appeared to be coated with black mold growth."
Some secondary fungi that grow on corn plants create what is commonly called "black corn," Sweets said. "Since they give the affected plants a sooty appearance, these fungi are sometimes called sooty molds. These sooty molds tend to develop on plants when wet or humid weather occurs as the crop is maturing, or when harvest is delayed because of wet weather."
She said environmentally stressed corn plants are more susceptible to the condition. The fungi are more commonly detected on plants that are shaded, undersized, weakened or prematurely ripened with decaying foliage. "Many of these corn fields had already been turning, some prematurely because of the drought conditions in the area," she added.
Despite its name, "the mold growth can range from black to olive green — or even pink to white," Sweets said.
Under some conditions, the molds can infect kernels, which might show a black discoloration. Because sooty molds and secondary fungi can weaken stalks, they can contribute to lodging, "especially if there are high winds or strong storms before harvest," Sweets said.
Grain from sooty fields should be treated with special care and thoroughly cleaned to remove lightweight, damaged, broken or moldy kernels, she said.
If those guidelines are followed, "black corn usually isn't a problem in the bin," said Bill Casady, MU Extension associate professor of biological engineering. "You'll want to look as some of those ears and see whether it's gone so far into the plant that it infects the kernels. Just make sure you reduce the temperature of the grain below 50 degrees, and it shouldn't affect the storability of your grain."
He described a combine going through a field as "a phenomenal sight. It makes what looks like a big cloud of black smoke as it goes through."
Casady cautioned that working around grains with sooty molds might pose a problem for people with mold allergies. "Get yourself a well-fitted respirator instead of one of those flimsy paper masks. And be sure to clean your filters out on the combine," he said, "both the filter for the cab and the one for the engine."
Forrest Rose is an Extension and ag information specialist with the University of Missouri.