The most common ear diseases in the Midwest are caused by Fusarium fungi. "Fusarium ear rot" or "Fusarium kernel rot" refer to the disease caused by Fusarium verticillioides, F. proliferatum and F. subglutinans.

Symptoms of Fusarium ear rots are a white to pink or salmon-colored mold, beginning anywhere on the ear or scattered throughout. Often the decay begins with insect-damaged kernels, but most of the ear can be affected. Infected kernels are often tan or brown-colored, or have white streaks.

Fusarium species also cause corn stalk rots.

The fungi survive on corn residue and the residue of other plants, especially grasses. Fusarium spores are spread by wind and splashing rain to the silks, which are most susceptible as they senesce and turn brown. Infection of kernels can also occur through the stalk, but this mode of kernel infection is less common.

Insect damaged kernels are very susceptible, and spores carried on the insects can infect the damaged kernels. Fusarium ear rot occurs under a wide range of weather conditions, and insect activity may be the critical factor determining Fusarium ear rot severity.

Gibberella ear rot (deoxynivalenol, zearalenone)

Gibberella ear rot on whole ear

Gibberella on shelled corn

Gibberella ear rot of corn is caused by the fungus Gibberella zeae, also known as Fusarium graminearum.

It can be identified most readily by the red or pink color of the mold. It almost always begins at the tip of the ear. In some cases, the color is too pale to be seen readily, so the mold appears white. In this case, it may not always be possible to distinguish Gibberella ear rot from Fusarium ear rot without microscopic examination.

This fungus also causes corn stalk rot and head scab of wheat; it survives in corn and small grain residue.

The spores of this fungus infect through silks; stalk infections are not believed to lead to Gibberella ear rot. Spores reach the silks by splashing water or they may be carried by insects. Infections may originate at insect wounds rather than at the ear tip.

Gibberella ear rot infections occur more commonly when the weather is cool and wet during the first five days after silking. Continued development of the mold also depends on subsequent cool, wet weather. Optimum temperatures for disease development are 65-70°F.

Head blight (Scab) of wheat (deoxynivalenol, zearalenone)

Fusarium head scab - partial killing of wheat heads

Fusarium head scab - shriveled, moldy seed from diseased head

The fungus that causes Gibberella ear rot in corn also causes Fusarium head blight (scab) in wheat and other cereals.

Disease symptoms include spikelets that appear bleached. Kernel development can be severely affected, causing barren spikelets and shriveled kernels. With less severe infections the kernels may appear pinkish in color.

The pathogen survives in corn and small grain residue, and the spores are released after each rain event. Optimum conditions for infection are 48 to 72 hours of head wetness and temperatures between 60-85°F.