Anthracnose is one of the most common stalk rot diseases faced by corn growers in the United States. In fact, yield losses due to anthracnose stalk rot can reach as high as 40 percent through reduced ear size and stalk lodging. Researchers with Pioneer Hi-Bred International, Inc., encourage growers to be aware of this disease and current methods of control.

“Growers may see stalk rot when the early-season growing environment encourages heavy kernel set and when the late-season environment is stressful,” says Gary Munkvold, research coordinator – pathology, entomology, and seed science for Pioneer. “Yield loss is due to reduced grain fill, premature plant death and stalk breakage or lodging.”

Anthracnose is caused by the fungus Colletotrichum graminicola. This fungus can attack corn plants at different stages, causing leaf blight and crown rot of seedlings. It also causes leaf blight, stalk rot and top dieback of adult plants.

“Growers can identify anthracnose stalk rot by the appearance of shiny black blotches or streaks on the stalk rind,” says Munkvold. “A gray mold also can appear in the deteriorated stalk pith.”

Stalk rot can be the result of the combined effects of more than one organism that attacks a plant approaching maturity. Therefore, identification can be difficult and other pathogens may be involved, including Gibberella, Fusarium or Diplodia.

Leaves above the ear may turn grayish green, yellow or reddish, then die and collapse. This is referred to as top dieback. Top dieback normally takes place four to six weeks after pollination, while the lower stalk remains green and before the lower leaves begin to wither and die.

Factors to prevent anthracnose stalk rot

Plants with stalk rot are vulnerable to lodging, so growers should monitor fields and combine fields with stalk rot first. Producers should begin scouting for stalk rot when corn reaches 30 percent to 40 percent moisture.
“Growers also need to keep in mind that prevention is the best weapon to keep anthracnose at bay,” says Munkvold. “Hybrid selection, crop rotation, insect control and avoidance of stresses due to fertility and moisture all help prevent anthracnose.”

Munkvold adds that corn growers should select hybrids with good standability and high yield potential that are recommended for their growing area. Pioneer® brand corn hybrids are currently rated according to their resistance to anthracnose stalk rot.

Crop rotation with nongrass crops in conjunction with a deep plowdown of corn residues is beneficial in preventing a buildup of the anthracnose pathogen in the soil. Balanced soil fertility, particularly that having adequate nitrogen and potassium, is important.

Any soil conditions that interfere with availability and uptake of water and nutrients also can promote stalk rot. That means growers should avoid soil compaction and herbicide injury, plant an appropriate population, control weeds and use good irrigation practices where available.

Damage from stalk-boring insects like European corn borer can promote stalk rot, so management should include control of these insects – such as that provided by Herculex® I and Herculex XTRA insect protection traits.

Pioneer Hi-Bred International, Inc., a subsidiary of DuPont, is the world’s leading source of customized solutions for farmers, livestock producers and grain and oilseed processors. With headquarters in Des Moines, Iowa, Pioneer provides access to advanced plant genetics, crop protection solutions and quality crop systems to customers in nearly 70 countries. DuPont is a science company. Founded in 1802, DuPont puts science to work by creating sustainable solutions essential to a better, safer, healthier life for people everywhere. Operating in more than 70 countries, DuPont offers a wide range of innovative products and services for markets including agriculture, nutrition, electronics, communications, safety and protection, home and construction, transportation and apparel.

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