Monitoring Corn Diseases
Two corn diseases farmers need to be monitoring again this year are vomitoxin and tar spot. Cooler temperatures especially at night and August rains tend to promote Gibberella (GIB) erot or vomitoxin. GIB is caused by a fungus named Fusarium graminearum , also called Gibberella zeae , causing ear rot, stalk rot, and head scab in both corn and wheat. Corn symptoms include a reddish or pinkish-white mold on the ear tips which is a toxin. The pathogen over- winters on plant residue, usually corn stalks/leaves and wheat residue (straw and chaff). GIB ear rot is most prevalent when cool wet weather occurs for about 21 days after silking. Fields most susceptible are corn after corn or corn after wheat, especially if the wheat was infected with Fusarium head scab. Corn that is stressed from lack of nutrients, by insects, or other types of plant stress (soil compaction, poor soil health) tend to have higher levels of GIB ear rot. Some corn varieties, when they start to dry, keep their husk up...