Rain may make grain, but it also caused some other problems this season, too.
You're not alone if you've peeled back corn husks this fall to find Diplodia, a white fluffy fungus covering the kernels. Cool, wet conditions during the growing season resulted in kernel damage ranging from 5% to 30% in many areas of the Corn Belt.
"Diplodia ear rot is first noticeable in the field by a bleached appearance of the husk. When you peel back the husk, you see a white fluffy fungus,” explains University of Illinois Extension integrated pest management specialist Suzanne Bissonnette. "It's not a new disease; it's been on an upward trend for the past decade or more, but this year it has been particularly bad.”
The good news is Diplodia fungus doesn't typically produce mycotoxins in the grain. The bad news is Diplodia causes lightweight kernels that reduce yield and nutritional value.
Diplodia ear rot is caused by the fungus Stenocarpella maydis, which overwinters on corn residue. Corn is the only known host for the fungus. The fungus appears as raised black fruiting bodies on moldy husks or kernels. If infection occurs early, the entire ear may be covered with mold. If infection occurs after silking, only a portion of the ear may be affected. Later infections may result in only a fine web of fungal growth on the kernels.
University of Illinois plant pathologist Carl Bradley says fungicides have little impact on the disease. The best course of action is to think about next year's hybrid selection and placement.
Bradley suggests choosing hybrids with the best resistance to Diplodia. Seed companies generally rate their hybrids for resistance to Diplodia.
"The good thing about a year like this one is that seed companies and growers should be able to identify differences in hybrids and will know which ones to avoid next year and which ones can resist Diplodia infections a little better,” Bradley says.
Avoid planting corn-on-corn next year in fields that were affected this year. The Diplodia fungus survives on corn debris, so planting right back into that debris can be risky.
"The days of the moldboard plow are gone, but burying residue from affected fields is one way to help deal with the inoculum that may be present next year. However, one has to balance between tilling for disease management purposes and prevention of soil erosion,” Bradley says.
"Following these two practices for next year will help with Diplodia management. However, when the environment is favorable for disease like it was in 2009, it's truly difficult to be able to have 100% disease-free fields,” Bradley adds.
- November 2009