Anthracnose in corn is caused by the Colletotrichum graminicola fungus which possesses the potential to cause early- and late-season leaf blight, stalk rot and “top-kill” or “die-back” (when upper leaves may die before those in the center). Corn anthracnose can be found throughout the Corn Belt from the Mid-Atlantic states to Nebraska.
While anthracnose is typically a secondary pest not likely to cause problems every year, it warrants a watchful eye for signs of infection throughout the corn growing season, including pre-harvest and post-harvest management for future crops. The disease can manifest itself when environmental conditions and other stresses create an ideal scenario for targeting high-yield corn potential. Corn anthracnose is most typically seen in no-till and reduced-tillage farming systems.
When corn is heavily infected with anthracnose leaf blight, lesions may merge to cover entire leaves, which wither and die.
The top die-back (Phase 2) stage of anthracnose is the most damaging to yield because of stalk rot and leaf loss. Phase 3 of corn anthracnose occurs late in the season, leading to lodging and harvest problems.
It’s possible for an early corn anthracnose infection in root stalks to cause plant death before pollination. A more common effect during the stalk rot phase is corn plants dying from anthracnose just before maturity. When several nodes are rotted, the entire corn plant dies. Compared to other types of stalk rot, lodging from anthracnose happens higher up on the corn stalk.
Overall, most yield loss from corn anthracnose results from premature plant death, which ultimately stops grain fill and causes lodging to complicate harvest.
Managing Corn Anthracnose
Farmers can benefit from several options to manage corn anthracnose, including hybrid selection, scouting, cultural practices and fungicides. A combination of these crop protection practices provides optimum security to enhance corn yields and should be implemented to sustainably manage corn diseases.
Choosing corn hybrids with genetic disease resistance offers the best economical and effective defense against corn anthracnose and other diseases. Be aware that corn hybrids with resistance to anthracnose corn leaf blight might not also have resistance to the stalk rot phase. Seek recommendations from a local seed dealer to determine corn anthracnose disease ratings and help determine the best hybrids for individual fields and regions. Even partial disease resistance goes a long way to protect corn yields.
Early and frequent scouting for diseases is a routine best management practice to tackle pest problems before they lead to economic damage. In the case of corn anthracnose, look for lesions on the lower seedling leaves. A hand lens can help detect black spots in lesion centers. The anthracnose leaf blight phase typically doesn’t occur after corn reaches knee-high. Following the leaf blight phase, scout for corn anthracnose symptoms every three weeks when plants are between the knee-high and whorl growth stages, according to University of Kentucky.
Crop rotation remains a solid tactic to help diminish disease threats. Any type of tillage that reduces crop residue from a previous corn crop will help manage corn anthracnose and other diseases overwintering in crop residue. When field history shows anthracnose disease problems, farmers may want to consider using tillage that chops and buries residue and rotating away from corn for a year.
A combination of integrated management practices such as disease-resistant hybrids, crop rotation, proper nutrient management and insect, weed and disease management – with chemicals, if needed – are especially recommended in continuous corn grown with no-till and reduced-tillage cropping systems, according to University of Illinois Extension.
Foliar fungicides may be applied early in the growing season to corn seedlings as a risk-management tool for anthracnose leaf blight and other corn diseases, including corn eyespot and northern corn leaf blight. When anthracnose leaf blight is identified, application during early corn growth is critical for maximum fungicide effectiveness.
Stratego® YLD fungicide from Bayer controls a broad spectrum of diseases; it combines the latest in triazole technology with a powerful, complementary strobilurin chemistry. This versatile fungicide can be applied early season and/or at tassel. The early-season application delays the onset of infection in the middle of the canopy and fights infections of the stalk. The tassel application protects the photosynthetic engine, the ear leaf and the surrounding leaves. Both applications are especially important for growers who are pushing for high yield production and/or farming in an area with a disease history.
Yield increases over untreated corn have been consistently demonstrated, with a 7-bushel-per-acre on average increase with use of an early-season application and a 12-bushel on average increase with use of a tassel application. Growers have been shown on average to gain 15 bushels when using both the early and tassel applications.
Keep in mind that an early-season fungicide application provides important protection and typically adds a yield increase to your crop. For cost efficiency, fungicides can be tankmixed with herbicides and applied in one trip across the field.
Before purchasing seed or applying any fungicide, please read the entire label for the best possible results and to confirm that the product is effective on the disease you need to control. Every product is not suitable for every situation, and correct application technique will ensure the best results.