While ear mold is always a concern in late-harvested corn, growers who find blackish mold in their fields on corn husks may not have ears that are infested with grain-damaging and toxin-contaminated mold. Rather, the mold could be a variety that may only impact the husks, according to an Ohio State University Extension plant pathologist. But growers won't know what kind of ear mold the fields may be infested with unless they examine the moldy-looking ears and send samples to a lab for testing, said Pierce Paul, who is also a researcher with the Ohio Agricultural Research and Development Center.
OARDC is the research arm of Ohio State University's College of Food, Agricultural, and Environmental Sciences. The concern for ear mold is higher than normal for some growers this year thanks to the drought, which created ripe conditions for the development of the fungal disease Aspergillus ear rot in some Ohio fields during the summer, Paul said. "Harvests that were delayed due to excessively wet conditions in areas that were affected by the drought during the summer and had problems with aflatoxin are of concern since delaying harvest may also increase aflatoxin contamination," he said. "Stalk, root and ear rots may also cause considerable damage in fields waiting to be harvested. "Root and stalk rots leave plants weak and highly vulnerable to lodging, while ear rots may lead to grain contamination with mycotoxins." The concern is that drought-stressed corn is more susceptible to infection by Aspergillus flavus, an ear rot fungus that produces a very potent group of carcinogenic (cancer-causing) toxins, called aflatoxins, which can be harmful for animals and for humans if used in corn for grain and human food consumption, Paul said.
Besides aflatoxins, other examples of toxins produced in moldy ears are deoxynivalenol (vomitoxin), zearalenone and fumonisin. But, just because the corn may have ear mold, not all ear molds are associated with mycotoxin contamination, Paul cautioned. "Don't just abandon your field if it looks dark and moldy," he said. "Some opportunistic fungi grow on the husk without affecting the grain. "These typically leave the ear looking dark and discolored, but when the husk is removed, the grain looks healthy and normal. If you see the ear looking ugly, don't assume you do or don't have ear rot. Pull the husk back and take a look at what is going on." To know for sure, Paul said it's best to pull multiple ears from around the field to send in to a lab for testing. "Growers are concerned when they see these black ears, but if the mold is an opportunistic fungi, the ear could be still good on the inside," he said. Samples from suspect fields should be sent to an approved laboratory to determine whether aflatoxins or other toxins are present and whether they exceed thresholds established by the U.S. Food and Drug Administration.
More information on aflatoxin testing and FDA thresholds is available at: http://www.rma.usda.gov/fields/il_rso/2012/aflatoxin.pdf
The Ohio State University
College of Food, Agricultural, and Environmental Sciences