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Harvest 2009 – moldy corn

November 6, 2009
From Wayne Schoper, Brown/Nicollet Extension Educator

Every cropping year is different and this year is no exception. The phenomenon we are seeing this year in area corn fields is the growth of a gray to black colored mold on the ears of corn as the plants stand in the field waiting to be harvested. This is because of several factors including the late harvest, high moisture corn and continuing wet harvest conditions. There are two questions that need to be answered. First, are the problems at this point significant ear and kernel rots that are damaging the kernels, or is the problem primarily superficial growth of fungi on the kernel surface? Both types of fungal growth on corn can cause greater problems with grain quality if the corn is not harvested and dried properly. The current problem with the gray mold appearing on the ears of corn in the field appears to be a superficial mold that has not gotten into the kernels as of yet. This type of mold is an opportunistic pathogen that shows up when wet conditions such as what we have been experiencing for the last several weeks shows up. It also appears to be several different species of fungi that are taking advantage of the wet, nutrient-rich environment that they need in order to grow. Once the corn is harvested, they should stop growing. If the corn is not stored and properly dried or is damaged, they may continue to grow and reduce grain quality. Depending on the type of fungus and the storage environment, these funguses may continue to grow and could potentially produce mycotoxins.

Several types of ear and kernel rots and fungal growth can occur on corn in Minnesota. Over the years Fusarium ear rot, Gibberella ear rot, and Aspergillis ear rot have all been identified as plant pathogens in area corn fields. In a normal crop production year they will not be present at harvest as conditions are not right for their growth and propagation. This year we have seen conditions that are perfect for their development.

So what can be done about this situation? Harvesting the corn and drying it down to storage moisture levels should do the trick. One recommendation would be to dry the corn down to 13% moisture instead of the usual 15%. If you suspect mycotoxin problems, check with your crop insurance provider to see what your coverage might be.

Article Photos

Wayne Schoper

If you are feeding the corn to livestock it might be a good idea to have the mold levels and potential mycotoxin levels checked at a reputable laboratory. The University of Minnesota has a good one. They have the Plant Disease Clinic which can identify types of fungal growth and kernel infection on corn. Their website can be accessed at and there is a charge for determining mold and fungus identity and infestation levels. Check with your veterinarian for other sources. We do know that livestock (swine, cattle, horses and poultry) are susceptible to certain mycotoxins. Horse owners need to be particularly cautious. The wide variety of molds has created a range of mycotoxin possibilities primarily vomitoxin, zearalenone and fumonisin. Prolonged cloudy weather such as we experienced during much of October provide perfect conditions for rapid growth and onset of these kinds of molds. Another cautionary note, Toxins concentrate in the distillers grains at levels three to four time the levels that are on the raw corn. Ethanol plants are doing quick screening tests for inbound grain, especially on low test weight corn.

The bottom line is if you are feeding 2009 crop corn to livestock on your farm, it would be a smart idea to have a feed sample submitted to a reputable laboratory to analyze any potential mold levels and make ration adjustments accordingly.



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