How do I know if I have Stalk Rots?

If you grew field corn in the 2021 growing season, you most likely encountered some stalk rots towards the end of the season. They are very common in the Northeast, especially when we experience a moist, humid July and August, and have the ability to reduce yield by at least 5% and up to 20%. Premature plant death and plant lodging are the primary causes of yield loss.

The most common stalk rots in the Northeast include Anthracnose Stalk Rot (Colletotrichum graminicola), Fusarium Stalk Rot (Fusarium moniliforme), and Gibberella Stalk Rot (Gibberella zeae).

Anthracnose Stalk Rot is known as the common stalk disease in corn. If you’re noticing your stalks turning black  and lodging when pushed, the most likely explanation is Anthracnose Stalk Rot. If you cut the stalk open, it’s likely you will se some internal stalk discoloration. Crop rotation, breaking up crop residue through tillage, and planting resistant varieties are management practices that can help you reduce your anthracnose pressure.

Fusarium Stalk Rot can be spread by wind and rain or overwinters in crop debris by mycelia. It progresses significantly through pollination and silking and prefers warm, dry weather. If you’re out in the field and are noticing some rotting around the roots or soft, spongy stalks, cut open the stalk and if you’re finding light pink or tan discoloration, it’s likely Fusarium Stalk Rot. Some management strategies include hybrid selection, crop rotation, tillage, and reducing any possible stresses, such as an insect invasion, if possible.

Gibberella Stalk Rot is caused by the fungus Gibberella zeae. Small, black fungal structures will form on the stalk – these are called perithecia. Similarly to Fusarium Stalk Rot, the inner stalk may turn a pink or reddish color. However, Fusarium Stalk Rot does not form perithecia on the outer stalk. Wind and rain typically transport the fungi, but insect damage may help the pathogen gain access to the plant. Warm, wet weather after pollination can increase the severity of Gibberella Stalk Rot. Similarly to Fusarium Stalk Rot and Anthracnose Stalk Rot, selecting hybrids with good stalk strength, crop rotation, tillage, and proper soil nutrition are all good management practices to help reduce the severity of Gibberella Stalk Rot.