Aspergillus ear rot is one of the most important and challenging corn diseases, but a new Purdue Extension publication can help farmers identify and manage its effects.
"Diseases of Corn: Aspergillus Ear Rot" is a free, three-page publication that covers disease identification, the danger to livestock, mycotoxin testing, minimizing losses and handling diseased grain after harvest, and disease management. It is available for download at http://www.extension.purdue.edu/extmedia/BP/BP-83-W.pdf.
While no commercial corn hybrids are resistant to Aspergillus ear rot, Purdue Extension plant pathologist Charles Woloshuk said farmers can take some steps to help minimize its growth.
"An important factor in preventing Aspergillus ear rot is to reduce stress on the corn plant," he said. "Hybrids that tolerate water stress and irrigation can reduce drought stress on the plant. Also, farmers should provide adequate nitrogen fertilizer and maintain appropriate fertility within a field."
Managing this disease is important, because the fungus that causes it produces mycotoxins inside the diseased corn kernels. A specific mycotoxin, known as aflatoxin, is a livestock liver toxin and potential carcinogen. Livestock that consume aflatoxin can be susceptible to suppressed immune systems, reduced weight gain, cancer or death.
"Toxicity varies among animal species, and young animals are most sensitive to the toxin," Woloshuk said. "Furthermore, when lactating animals consume contaminated grain, the aflatoxin is present in the animal's milk."
The U.S. Food and Drug Administration has identified action levels, or regulations, based on the amount of aflatoxin present in relation to the grain's end use.
For example, in grain used for human consumption, animal feed or feed ingredients intended for dairy animals aflatoxin levels cannot exceed 20 parts per billion.
"Accurate mold identification is critical for making the right feeding and management decisions, so producers should confirm any mold identification at a diagnostic laboratory," Woloshuk said.
The Purdue Plant and Pest Diagnostic Laboratory (www.ppdl.purdue.edu), offers mycotoxin testing.
Once corn is in the ground and as harvest approaches, Woloshuk said farmers should scout their fields for Aspergillus ear rot by collecting multiple ears from several locations and checking them for olive-green mold - an identifying trait of the disease.
If areas of the field have rot, farmers should avoid them during harvest. Fields with extensive disease should be harvested as early as possible and dried to moisture levels that stop fungus growth.
"Late-season rains also will contribute to increased aflatoxin contamination," Woloshuk said. "Once harvested, corn must be dried to below 15 percent moisture to prevent further fungal growth and mycotoxin production."
Grain storage information is available from Purdue's Post Harvest Grain Quality website at www.grainquality.org.