While there is no way to manage or reduce toxic ear rots at this point in the growing season, Purdue Extension plant pathologist Kiersten Wise
said it's important for farmers to know what's present in their fields.
Aspergillus ear rot, common on drought-stressed plants in overly hot, dry crop years, is caused by the Aspergillus flavus fungus, which also produces aflatoxin. Aflatoxin is a mycotoxin that is carcinogenic and can cause health problems in livestock.
Infected ears are stunted and have an olive-green dusty mold under the husk.
"Low levels of Aspergillus ear rot were detected in 2010 in southern Indiana, and conditions may again be favorable for the disease to develop in 2011," Wise said.
Another common ear rot exacerbated by the hot, dry weather is Fusarium ear rot. Fusarium is caused by a fungus called Fusarium verticilloides, which produces fumonisin - a mycotoxin especially toxic to horses and swine.
Wise said symptoms of Fusarium ear rot include white, pink or grey kernels scattered across the ear. It often is associated with insect damage. "In some hybrids, a white streaking can appear in kernels, which is known as a 'starburst' pattern," she said.
Diplodia is another common Indiana ear rot. Wise said it usually first appears in the southern regions, but it can be found statewide in most years. The fungus that causes Diplodia ear rot is called Stenocarpella maydis. It infects corn during silking. What sets apart Diplodia from Fusarium and Aspergillus ear rots is the infection and disease development favored by wet weather.
"April-planted corn in southern Indiana experienced wet, humid weather at silking, which may have favored infection in susceptible hybrids," Wise said.
Infected ears tend to have bleached husks with tiny black specks on the outer layer.
Growers removing the husk of an infected ear will find white, fuzzy growth between kernels, often starting at the base of the ear. Cobs also can appear rotted.
Wise said producers need to scout their fields before harvest to determine if or how much of the disease is present.
"If any Aspergillus ear rot is observed in a field, affected areas should be harvested early and grain should be segregated to avoid aflatoxin contamination of non-infected grain," she said. "Fields affected by Diplodia and Fusarium ear rots should also be harvested prior to other non-affected fields.
"All grain contaminated by any ear rot fungus should be stored separately from good grain and stored below 15 percent moisture to prevent further growth of fungi."