MISSISSIPPI STATE -- As if the drought wasn't hard enough on this year's corn crop, growers now prepare for harvest with the threat of yield-reducing corn borers and a drought-related fungus.

Dr. Scott D. Stewart, assistant Extension entomology specialist in Raymond, said most of Mississippi's crop has damage from corn borers, especially in the Delta counties.

"Last year's mild winter and the increasing corn acreage probably combined for a larger-than-normal first generation of corn borers. The second generation usually causes the most damage," Stewart said. "Many fields were treated at least once, but there will not be any need to treat this third generation because of the crop's growth stage."

Dry conditions in early summer reduced much of the state's corn potential, but corn borers are the biggest yield reducers in irrigated fields. As their name implies, these pests bore into the stalk and where the ear attaches, impeding nutrition and weakening the plant.

"A bad storm will increase the damage caused by the corn borers by knocking over the weakened stalks," Stewart said.

An additional threat lurking around Mississippi's dry land corn is aflatoxin, a fungus that may grow on corn kernels.

Dr. Erick Larson, Extension corn specialist at Mississippi State University, said aflatoxin tends to increase during excessively hot, dry summers. It is usually a bigger problem at the beginning of harvest because fields that were most stressed mature first. Grain elevators reduce prices for infected corn or reject whole truckloads if the contamination is extreme.

"Producers can minimize the threat of aflatoxin buildup in the field by harvesting early. Harvesting early reduces fungal exposure to warm, humid conditions during dry down by artificially drying the corn," Larson said. "Wet grain that is not dried quickly during warm conditions will begin heating up to intolerable levels rapidly. Therefore, dry any wet grain to below 15 percent moisture within 24 hours or haul to an elevator immediately."

Larson said growers should not store wet grain in trucks, combines, bins or any non-aerated site more than four to six hours before beginning drying.

Don Smith, agricultural Extension agent in Adams County, said aflatoxin reports from Louisiana have him concerned, but it is too early for Mississippi growers to report problems.

Corn is typically accepted if it has up to 20 parts per billion of aflatoxin. In Louisiana, reports have ranged from 300 to 1,400 parts per billion. Corn at that level of contamination cannot be fed to poultry or livestock. Young animals are more sensitive to aflatoxins, and poultry and swine are more sensitive than cattle and sheep. Lactating dairy animals are a special concern because low levels of aflatoxins in the feed can result in unacceptable levels passing into the milk.