Ear and Kernel Diseases
Part 2, Section 2: Corn Pest Management
Corn Pest Management
DISEASE MANAGEMENT
Ear and Kernel Diseases
Ear and kernel diseases are important to diagnose mostly due to the possibility of mycotoxin production (see Moldy Corn and Toxin Production below). In addition to toxin production, ear and kernel diseases cause reduced test weight and lower nutrient values. Many of these diseases are often associated with insect or other damage to the ear. The best method for halting fungal growth is proper drying of the grain to 13 percent moisture or less, but neither drying nor heat will reduce mycotoxin levels if present.
Aspergillus ear rot is usually not an economic disease due to the fact it only colonizes a few kernels and not an entire ear. The signs of the disease vary depending on the age of the infection, usually yellow-green fungal masses that turn to dark green or brown.
Diplodia ear rot infects the plant just after flowering. Typical signs of Diplodia on the ear are a white or grayish mass of mycelium with black structures, pycnidia, produced on the husks, kernels, cobs, and even the stalks. This disease overwinters within infected debris and can be troublesome in continuous no-till planted corn. Crop rotation and fall tillage has been known to reduce the inoculums levels.
Fusarium kernel or ear rot is most severe when hot, dry weather occurs at or just after flowering. The sign of this disease is often a whitish-pink fungal growth on kernels. This disease can also be seen on the tip of the ear associated with insect damage from earworms or other pests. In severe cases, the entire ear may exhibit signs of the disease. The major concern of this disease is the likelihood of mycotoxins produced in the corn grain. The Fusarium family of pathogens is very good at overwintering on debris; therefore, crop rotation and tillage will reduce inoculum levels in severely infested fields.
Gibberella ear rot is characterized as a reddish mold that starts at the tip and grows down the ear. In severe cases the entire ear may be affected. This disease is also associated with Gibberella stalk rot of corn as well as Fusarium head blight (scab) of wheat. The stalk rot is also characterized by reddish-pink discoloration inside the stalk. Again, the major concern is the potential of mycotoxin production. The association of Gibberella with both corn and wheat has lead to high levels of Fusarium head blight in wheat following corn silage with high levels of stalk rot. In severely infected corn fields, crop rotation and tillage will help to reduce inoculums levels.
Penicillium ear rot is commonly found on ears with insect, bird, or other damage. The sign of this disease is powdery green or blue mold between kernels, usually near the tip of the ear. This disease is not often considered economically important in corn for grain, but it can pose problems in both high-moisture corn and corn silage.
