Bill Wilcke, Minnesota Extension Engineer
The combination of low grain prices and an unusually warm fall have created a greater-than-normal spoilage risk for stored grain in the upper Midwest. We have a large amount of grain in storage, including some that was harvested in 1997. Much of this grain is too warm, some is too wet for safe storage, and some of it is stored in structures and piles where there is inadequate aeration and poor protection from precipitation and soil moisture. Because of the high spoilage risk created by these conditions, stored grain managers should check their bins more frequently than normal to catchinsect and mold problems before they get out of control.
When grain is stored for more than a year and the grain temperature is high during part of that storage period, there is a high probability of infestation by insects. We have already heard a number of reports from grain managers who are finding insects in 1997 grain. If you find insects in stored grain during winter months, one of the best options is to aerate the grain during cold weather to slow insect activity and perhaps even kill the insects. We normally suggest that grain be cooled to 20° to 30°F for winter storage, but if you have an insect problem, you might try cooling the grain to temperatures even lower than 20°F and holding the grain at that temperature for a few weeks. Most insects become inactive at low temperatures and many die. Cool the grain as fast as you can because faster cooling gives insects less time to adjust to the temperature change and more of them will die. (Watch for frost build-up on screened roof vents in bins that have positive pressure aeration systems because restricted vent areas can lead to damaged bin roofs. Open roof hatches if frost starts to accumulate on vents.) If you use this low-temperature strategy to control insects, it would be best to run the fans again later in the winter to bring the grain temperature up to 20° to 30°F to reduce the temperature difference between the grain and outdoor air when warm spring weather arrives. (Large temperature differences can lead to moisture migration and condensation.)
Another strategy for reducing existing insect problems is to run grain through a grain cleaner during grain transfer operations. Grain cleaning removes many of the broken grain kernels that attract insects and removes some of the insects as well. Fumigating stored grain is generally not an option during winter. The type of grain fumigant most commonly used on farms does not work well at low temperatures and in fact, the label indicates that the product should not be used at low temperatures. Try non-chemical strategies first, and if they don’t work, wait until spring to fumigate the grain. Grain fumigants are potentially dangerous materials that require use of safety and gas monitoring equipment, so consider hiring a commercial applicator if fumigation is necessary.
Much of the 1998 crop was harvested at unusually warm temperatures and since it was unusually warm much of the fall, there were few opportunities to cool grain to the normal target temperature of 20° to 30°F. If grain has not been aerated since harvest, do so as soon as possible. If grain was aerated, but the temperature was greater than 30°F during the time that the fan was on, complete another aeration cycle during 20° to 30°F weather. If the bin is not equipped for aeration, feed or sell the grain as soon as possible or move it to a bin that is equipped for aeration. Holding warm grain into cold weather is very likely to cause moisture migration which leads to molding, crusting, and possible insect infestation at the top center of the grain mass.
Some of the 1998 crop was also stored at moisture levels that are too high for safe storage. The warm fall led to rapid field drying, and to save money, some farmers put crops (especially corn) directly into storage without any artificial drying. In some cases, the corn didn’t get quite dry enough and is now in storage at 15 to 17% moisture. If cooled to 20° to 30°F, corn at this moisture can be held through the winter without spoilage, but it should be fed, sold, or dried to less than 15% moisture before spring.
Finally, part of the 1998 crop was stored in outdoor piles or in structures that were not originally designed for grain storage. Keep an especially close watch on grain in these situations, because in many cases the grain is exposed to precipitation or soil moisture, and aeration systems (if present) often do not provide uniform airflow. If you see signs of moisture migration, mold, or insects, aerate to try to control the problem and feed, sell, or move the grain as soon as possible.
This page is part of the Biosystems and Agricultural Engineering Department web at http://www.bae.umn.edu/