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Storage & Handling

Storage and Handling

Corn Bin


Managing Moldy Grain
Purdue Extension publication ID-418

Grain Drying, Conditioning, and Aeration
Purdue Post Harvest Grain Quality and Stored Product Protection Program

Choose wisely: Avoid unprofitable strategies to manage moldy grain
Article from Purdue specialists on Purdue's Corny News Network

Alfatoxin Testing: Illinois, Indiana, Michigan, Ohio (PDF: 34 KB)
USDA-RMA publication provides information about aflatoxin testing laboratories.

Harvesting, Handling, and Drying Corn with Ear Rots in 2009 (PDF: 61 KB)
Although it focuses on 2009, this PDF from Purdue describes good post-harvest practices.

Chat ‘n Chew Café: Crop Maturity, Disease & Harvest Issues
A collection of articles about the moldy 2009 growing season

Frequently Asked Questions

What implications do the presence of mycotoxins and molds have for changing storage practices?
More careful management will be needed. Once the corn reaches a safe storage moisture and has been cooled to 35°-40°F, it should be monitored weekly, or at least every two weeks. Monitoring should be more frequent when air temperatures begin to increase in the early spring. If the bin is not equipped with temperature cables, a metal rod can be pushed into the grain mass and allowed to remain for at least 15 minutes, preferably longer. If fungi begin growing in the stored corn, they will produce heat and that will be detected by an increase in the temperature of the rod when it is removed from the corn. Grain is a good insulator — grain that is 3 or 4 feet from a hot spot may still be cool. Therefore, insert the rod several different places in the bin to help detect isolated hot spots.


How should I store affected grain?
Dry corn between 0.5 and 1.0 point less than the moisture content at which the corn is kept during normal years. For example, if you normally store corn at 15.5 percent moisture, store grain suspected of being moldy at 14.5 to 15.0 percent moisture. It's also recommended that corn be removed from the center of the bin by "coring." This involves opening the center well of the unloading auger and removing at least one or two loads of grain from the bin. The fine material usually concentrates in this center core of the bin and removing this corn removes that fine material. It also allows air to move through the grain mass more easily. In addition, the top surface of the grain in the bin should be leveled. Air finds the path of least resistance and all of the grain in the bin should be at approximately the same depth to ensure there is even airflow throughout the grain mass.


What is the most important action I can take to manage my stored corn?
Adequately dry the corn and keep it cool. In a crop year with high mold pressure, dry stored corn to 0.5-1.0 percentage points below the normal safe storage moisture (see above).

In addition, frequently inspect stored corn — at least every two weeks during the winter and weekly after outside temperatures begin to rise in late winter and spring. Turn on aeration fans and check the exhaust air for foul odors or an increase in temperature. Both indicate that fungi may be growing in the stored corn.


Is freezing corn a good strategy to slow development of mold and mycotoxins?
Fungal activity is greatly diminished once shelled corn is cooled below 40°F. If the corn is uniformly cooled to 35°-40°F and held at that temperature, it can be safely stored through the winter. There is little if any additional protection against mold growth that can be attained by freezing the corn. Regardless of the temperature at which the corn is held during the winter, take care when aerating the corn with warmer air. When warm and humid ambient air is blown through frozen grain (or even cool grain), the cold grain can cool the air below its dew point, which causes condensation on the kernel surface. This creates ideal conditions for mold growth. If insect growth in the stored corn is a concern, then freezing is an option. Although it will kill adult insects, it will not affect insect eggs.


Why is a load of corn sometimes rejected by an elevator one day and then the same load is accepted a day later?
This is usually caused by sampling variability. If several extremely moldy kernels are included in the grain sample taken from your truck or grain wagon, the level of toxins in the sample can easily exceed acceptable limits. If a second sample is taken and it happens to contain fewer moldy kernels, then the level of toxins in the second sample may be within acceptable limits.

You can greatly reduce sampling variability by gathering larger samples from an incoming shipment. The initial sample should be between 2.5 and 10 pounds (preferably 10). Reduce the larger 10-pound sample to a smaller, 2.2-pound representative sample using a Boerner Divider or similar device. Grind this subsample. About 0.11 pound (50 grams) of the ground corn is used for the mycotoxin test.


For More Information

Matt Roberts, Extension Associate, Agricultural & Biological Engineering
(574) 529-0019, Email:

Richard Stroshine, Professor, Agricultural & Biological Engineering
(574) 494-1192, Email: