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...

  Late season diseases are occurring in corn and soybeans. Tar spot in corn and sclerotia or white mold plus soybean cyst nematodes (SCN) in soybeans. In many cases, it’s too late to prevent the diseases. However, there are some management practices to reduce future incidences of the diseases. For corn tar spot, the symptoms include irregularly shaped black structures on leaves. The black structures are firm, appear mostly smooth on the surface and the spots do not rub off or break open. Tar spot can also produce black spots circled by tan lesions with dark borders. Tar spot overwinters on surface crop residue. The spores are dispersed by the wind and rain droplets splashing the inoculum onto plants. The inoculum likes cool summer conditions with adequate moisture and high humidity. The recent August rains with cooler days and nights is causing good growing conditions. Field with a history of tar spot are most susceptible. The best time to apply a fungicide is at tasseling (VT) up ...