I May Have Moldy Corn. Now What?

It was too wet. It was too cold. It was too dry. Then Hurricane Ike washed through droughty corn. Delayed maturity threw drydown schedules in the garbage. Despite the fact that some farmers forward contracted corn for nearly $8 per bushel, the quality of the crop may result in dockage that will not allow settlement prices anywhere near those historic marks. The challenge du jour will be to identify the problems, manage them, and understand why crop quality deteriorated this year.

Many farmers have reported molds in their corn fields. If you have it, you are not alone, but it needs to be identified before it can be managed in on-farm storage. If you take it to the elevator, don’t be surprised if it is found in the moisture sample.

Iowa State agronomist Roger Elmore, plant pathologist Alison Robertson, and grain quality specialist Charles Hurburgh look at the mold problem in a new fact sheet on quality issues.

The specialists say the cool, wet fall favored the development of fusarium, which will form a white or pink mold on moist corn. Their production of toxins, including vomitoxin, zearalenone, and fumonisin, can create serious health issues for humans and livestock. While corn harvest is continuing to move rapidly, their recommendation is to harvest moldy corn first, to halt production of the mycotoxins and dry the corn as soon as possible.

Diplodia ear rot has been common as well, but while it will not produce mycotoxins, it will rapidly deteriorate the quality of the grain if left in the field longer than necessary.

For infected corn, dry to a moisture level under 15%, and cool to a temperature less than 45 degrees, which should curtail mold growth and mycotoxin development. If you have mold-damaged corn, do not plan to hold it beyond the winter.

It may be tempting to blend moldy grain with high quality grain, but that will only cause the mold to infect a larger quantity. Even harvesting should be arranged to avoid moldy corn, which could be found around ponded areas or in parts of the field where corn plants were more immature, or on the ground. Samples should be left in the field for crop insurance adjustors to examine.

Before feeding moldy corn to livestock, beware they will be sensitive to the toxins, which could be fatal, and in the case of dairy cows, their milk will carry the toxins. If the moldy corn is sent to an ethanol refinery, the DDGS will have a toxin content 3-4 times that of the original corn. For more information on handling moldy corn and what can be done with it, consult Iowa State’s publication about aflatoxins in corn.

For corn that escaped molds in the field, measures should be taken once it is in storage to prevent mold growth and the future development of mycotoxins. Hurburgh and Elmore’s fact sheet on grain storage management acknowledges that more wet corn will be held this year because of the expense of drying. They recommend weekly checks to see if the temperature of the grain is rising. They also say wet corn should have twice the amount of air moving through it as dry corn.

If you have more wet corn than drying capacity, the specialists recommend drying to 17-18% moisture and cool in the storage bin, which will result in 16% moisture corn. Or the corn can be dried to 20% moisture, cooled in the bin, but it should not be held into the spring. Another recommendation is to remove the center core, where fines build up and increase the potential for mold growth.

The Iowa State specialists also report in a new fact sheet on test weight and moisture that the lack of good drying weather in late October may mean the corn will naturally dry to no more than 17-18%. They expect the high cost of energy will cause many farmers to hold corn at higher moistures over the winter, hoping for better drying opportunities in the spring.

Another problem is a lower test weight which results from a long, cool growing season with high grain moisture. The lower test weight means less protein and more starch. Food processors will be impacted and may impose a dock. Ethanol refiners will not be affected by the lower test weight, unless they are guaranteeing the quality of the DDGS they produce.

Your planting date and hybrid selection may also impact the test weight, say the specialists, “Early planting dates, higher N rates or less N loss, lower plant populations, and years with better growing conditions all contribute to higher test weights. Loss of N from extreme rainfall may be a contributing factor to lower test weight this year.” They add that low test weight corn should not be stored into warm weather and should be dried below 15% moisture.

Summary:

A challenging year to grow corn has also resulted in a crop with quality challenges. There have been numerous reports of mold, which not only produce mycotoxins that jeopardize livestock feeding, but also jeopardize its storability past the winter months. Corn with mold should be dried and cooled to levels below normal, should be checked for toxins, and should not be kept into the spring when outside air temperatures rise. The 2008 growing season has also created conditions to promote low test weight on corn, which means its content has more starch and less protein.

Author: Stu Ellis
The Farm Gate - University of Illinois Extension