By Frank J. Buchman
As corn harvest is moving fast forward across Kansas and the Midwest, producers are experiencing another problem, according to Don Peterson of Santa Fe Ag Services at Council Grove.
Abundant rain fall has expanded corn yields in many locales, helping combat sharply lower corn markets than just a couple of year.
But, high moisture conditions have sometimes been most enhancive to intrusion of ear rot disease, Peterson informed.
“The increase in no-till or reduced-till fields and the repeated planting of corn without rotation increase the likelihood that root rot disease will be present in the field,” explained Charles Woloshuk, plant pathologist at Purdue University.
“Hybrid genetics and, yes, the wet weather are also major factors that contribute to disease development,” Woloshuk acknowledged.
Ear rot is not easily recognized, but the most severely affected ears will be completely rotted with visible mold that is grayish or brown on and between kernels. The noticeably light weight ear will be standing on the stock, and not drying down, Woloshuk explained.
In less severe infections, the mold will appear white to grayish, visible on and between the kernels, but only affecting part of the ear.
“The disease typically starts at the base of the ear progressing toward the tip, while infected kernel tips are discolored,” Woloshuk said.
Sometimes disease symptoms are just on the tip-end or middle part of the ear. There are generally black specks scatted on the husk, cobs and sides of kernels.
Biggest problem is that the corn value deteriorates. “Corn will result in potentially significant discounts when graded at the first point of sale,” Woloshuk said.
Lightweight kernels lower the test weight. “Moreover infected corn results in more cobs and kernels being ground up during the combine shelling operation, which results in higher levels of broken corn and foreign material,” Woloshuk said.
Ear rot kernels will easily break during post-harvest handling, causing an increase in the amount of fine material in a storage bin. “These fines will decrease airflow during aeration, which will increase the potential for spoilage,” Woloshuk insisted.
“Pre-cleaning, especially after drying and before delivery or storage, is highly recommended to remove the lighter weight damaged kernels, cob pieces, fines, and foreign material. This will help to minimize discounts and improve storability of the corn,” Woloshuk advised.
Proper storage of infected corn is crucial. “Drying the grain to 15 percent moisture will stop further growth of the fungus,” pathologist said.
“However, other fungi, which can grow at 14 to 15 percent moisture, will find it easy to invade the ear rot damaged kernels and cause further spoilage, damage, and self-heating,” Woloshuk continued.
“If ear rot is significant, the grain should be dried to below 14 percent and cooled to below 50 degrees as quickly after harvest as possible. Infected grain should be stored at 30 degrees, and storage time should be limited to the cold weather season,” Woloshuk said.
Corn debris that remains on the soil surface will overwinter and provide a source of ear rot infection for the following year.
“Infection is also enhanced by dry weather prior to silking, followed by wet conditions at and just after silking. Ears are most susceptible to this disease during the first 21 days after silking,” Woloshuk said.
“To prevent a reoccurrence of ear rot, avoiding reduced-tilled corn following corn is advised,” Woloshuk said. “Rotation out of corn will allow corn residue to degrade, reducing the presence of the pathogen.”
Corn hybrids vary in susceptibility to ear rot. In areas where the disease is problematic, a resistant variety should be considered.