Last week I touched on fungal diseases that can affect the soybean crop. Corn, too, has its share of fungal enemies. Corn fungus infections reduce the yield, damage the quality of the crop, and reduce its value as feed, so it’s well worth taking these infections very seriously. As you might expect, the wetter the season the bigger the potential for fungus problems – but some fungi do exceptionally well in dry conditions, so don’t assume you’re safe just because it’s been sunny lately. Damage to the kernels from birds or insects (who leave holes in the husk, allowing fungus to penetrate) also makes life easier for our fungal friends.

Aspergillus ear rot is a grayish-green powdery mold that starts at the tip of the ear and spreads along damage caused by insects. The infection can take root anytime from silking on, and isn’t stopped by dry conditions. Aspergillus produces aflatoxin, which is dangerous to people and livestock both. Elevators test corn for aflatoxin levels, and will reject bushels that exceed FDA limits.

Diplodia ear rot commonly hits in fields that are grown with reduced tillage, or that are continuously planted with corn. The fungus shows as a white or gray mold at the base of the ear and gros between kernels. Diplodia gets a big boost from wet weather within three weeks after silking, so watch for it then.

Fusarium is a kernel rot that shows up as white or pink streaks that look like stars, scattered over the entire ear. Fusarium gets its start at places where the ear is damaged from insects, and from kernel growth cracks. Fusarium produces fumonisin, a mycotoxin that is deadly to livestock and especially to horses. Fusarium gets a boost from warm, dry weather.

Gibberella begins at the tip of the ear and progresses down towards the butt. It is red or white, with pink being the most common shade observed. Gibberella produces both vomitoxin and zearalenone, both of which are harmful to livestock. Gibberella does best in cool, wet weather after silking, through the late summer months.

Penicillium, also known as “blue eye”, grows on and between kernels, particularly those damaged by worms, corn borers, or machinery. Corn stored with high moisture levels is particularly susceptible.

Trichoderma produces a green mold that grows on and between husks and kernels. Trichoderma gets its start through insect or mechanical damage. Trichoderma generally doesn’t do much damage on its own, but you should learn what it looks like so you won’t mistake it for the much more dangerous Aspergillus, which it sometimes resembles.

Managing these fungal pests can be quite a hassle. Many ear rot fungi can stay alive in the soil for years, so thoroughly scout fields that have had ear rot in recent years. Crop rotation, heavy tillage, and planting a mixture of hybrids are all good ways to minimize the impact of fungal infection on your crop.