, Farm Journal Seeds & Production Editor
Rain keeps falling on the corn parade. Wet, cool conditions do more than delay harvest, they also favor moldy corn. Damage reports exceeding 50% have been filtering in from some parts of the Corn Belt.
There's a lot of Diplodia fungus showing up in corn fields this year, says Suzanne Bissonnette, University of Illinois Extension Integrated Pest Management specialist. "It's not a new disease and it's actually been on an upward trend for the past decade or more, but this year it has been particularly bad.”
Bissonnette says Diplodia doesn't typically produce mycotoxins in the grain. Mostly it causes damage to corn by causing lightweight kernels that reduce yield and reduces the nutritional value of affected grain. Under most conditions damage is limited to the field, but it can be a problem in storage if grain moisture is 20% or above.
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. Cobs can take on a mummified appearance.
Diplodia ear rot is caused by the fungus Stenocarpella maydis, which overwinters on corn residue. Corn is the only known host for this fungus. A specific characteristic of Diplodia ear rot is the appearance of raised black fruiting bodies of the fungus on moldy husks or kernels. The fungus causing Diplodia ear rot can also cause a stalk rot.
Bissonnette observes that other, more toxic, molds are also showing up this season too. "Wet years can also produce mycotoxin-type molds like Fusarium or Penicillium, but they tend to be pink or bluish-green in color,” she says.