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Ear rot infections raise questions

Question: What causes ear molds in corn?

Tina Lust: Ear molds were prevalent in many fields across the Corn Belt this fall. Wet, cool weather going into fall, delayed harvest, and the fact that later-than-average planting led to later-maturing fields provided an ideal environment for ear rots to flourish where infection occurred earlier in the growing season. Due to the cooler growing season, corn plants did not mature normally, and husks did not loosen up in some cases, harboring moisture and creating the perfect environment for fungal growth.

Question: What caused infections this year?

Lust: The biggest problems were diplodia ear rot and gibberella ear rot. Both are soilborne fungal infections favored by certain weather conditions. Some of these ear rots create major issues for grain quality because the fungi that cause them produce mycotoxins, which are poisonous to livestock.

Question: Are the two fungi different?

Lust: Diplodia ear rot is characterized by the fungus Stenocarpella maydis. The high levels of infection observed were a result of frequent rainfall just before and throughout silking; ears are most susceptible to diplodia from silking to about three weeks later when rain splashes infected soil particles on the silks.

Gibberella ear rot is caused by the fungus Gibberella zeae, a form of the fungus Fusarium. This disease is favored by hot and dry conditions at pollination and high humidity.

Question: How can you spot problems?

Lust: The first symptom of diplodia is bleached husks. Later symptoms are characterized by white mold growing on and/or between rows of kernels. Ears affected within two weeks after silking appear to have kernels “cemented” to the cob, or “mummified”; in later infections a light, cottony growth may be observed growing from the ear.

Question: How should stored corn that has ear rot be managed?

Lust: To avoid the spread of molds to unaffected kernels in storage, it is important to dry grain below 15% moisture for long-term storage. In general, damaged grain will not store well beyond the winter months. Temperatures need to be kept as cool as possible; 40 degrees F or lower would be desirable. Market the grain as soon as possible. Moldy grain should always be tested before being fed to livestock.

Question: Can this problem be prevented?

Lust: Rotating away from corn and burying residue may help reduce levels of inoculum in the soil. The fungi that cause ear rots survive in residue, so practices that encourage residue decomposition reduce the risk of ear rots. Select hybrids with a good disease package that have a higher resistance to diplodia, gibberella and fusarium. Keep records of which fields show signs of disease.

Meet the adviser

Tina Lust
Channel Bio Corp., Marion

There are more than 550 Certified Crop Advisers in Ohio certified through an international program to enhance the professional advice farmers receive. If you have a question for a CCA, please e-mail it to the editor at twhite@

This article published in the February, 2010 edition of OHIO FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.