Moldy Corn and Toxin Production
Part 2, Section 2: Corn Pest Management
Corn Pest Management
DISEASES
Moldy Corn and Toxin Production
In recent years, there have been many reports of corn fields in which 30 to 50 percent (occasionally a greater percentage) of the ears are colonized by fungi to such an extent that the problem is readily apparent to growers. Several species of fungi are responsible for producing these “moldy ears,” and they are present wherever corn is grown in the state. Corn that dies prematurely usually shows excessively high moisture content in the grain, and this favors fungal growth. Wet weather during the drydown period also promotes mold growth.
Once the crop is harvested, the combination of high grain moisture levels and warm temperatures will favor fungal growth. A kernel grain moisture content of 15 percent is the critical point for mold growth. Grain falling below this moisture content percentage does not support mold development; moisture levels greater than 15 percent do support mold growth. Temperatures in the range of 40 to 50°F restrict most mold growth, while temperatures of 70°F or above promote it. Therefore, once the crop has been harvested, proper storage is critical.
Ear corn continues to dry when placed in properly designed cribs. The grain moisture content, however, should be 21 percent or lower when the crop is placed in the crib. High-moisture (greater than 25 percent) ear or shelled corn will heat up and develop molds rapidly; this corn should be ensiled immediately after harvest. Failure to do so will result in moldy, low-quality feed with a high risk for mycotoxin contamination.
Bird and insect damage to the ear before harvest can contribute to an increase in the incidence of ear molds. Ears in contact with the ground remain moist, promoting fungal growth. Excessive numbers of cracked or broken kernels promote mold growth, so proper combine adjustment also is important.
The primary concern in moldy corn is the production of mycotoxins. These poisonous components are by-products of fungal growth on the grain and can cause problems when fed to livestock, including poultry and horses. Although these toxins may not adversely affect cattle, the mycotoxins can be secreted into the milk. The toxins produced depend on the species of fungi growing on the ear. The potential for toxin production on corn occurs throughout the state. If you have experienced more than trace amounts of ear rots (moldy corn), consider having your grain tested for toxins, and follow recommended feeding practices if the results are positive. Contact your county extension educator for the names of public and private laboratories that conduct toxin tests.
