Time to Check Stored Grain for Insect Infestations

Published: February 10, 2010

Just a reminder that it is important check the condition of on-farm stored grain at this time. Differences in grain mass temperatures of several degrees may indicate that insect and mold problems are present. If the grain mass was properly dried this past fall, any insects present in the grain mass should be inactive if the temperature of the mass is 50-60 degrees Fahrenheit or lower. If the grain is to be held in storage into the summer months and no insecticide was applied in the fall, then the grain may be at risk from insect pests. To determine if insects are present at this time, you should do a visual inspection of the top of the bin to see if any insects or insect damage is present. A sour smell, grain clumped together, condensation present on the inside surface of the bin roof, webbing on the grain surface, or the presence of insect larvae, adult beetles or moths all suggest the presence of an insect infestation.

Scouting methods differ by location in the bin. Indian meal moth infestations can generally be seen by observing the top of the grain mass from the roof access door. If no webbing or foul grain odors are found, then it is unlikely that Indian meal moths are present in high numbers. If the grain was properly leveled and treated after filling of the storage structure the previous fall, it is best not to break or disturb the protective cap of insecticide applied at that time. Some probing of the grain surface from the access door may be necessary to determine level of insect infestations if found. Scouting for stored grain insects in the grain mass can be accomplished by using a grain probe to collect samples from the side access panel. Grain collected should be placed in a glass jar, plastic bag, or some other container through which insects can be seen if they are present in the grain. These containers of grain should be placed in a warm area to allow the grain to warm to at least 60 degrees F or higher in order to stimulate insect activity.

If an insect infestation is found on the surface of the grain mass and webbing is present, this usually indicates the presence of Indian mealmoth. As this insect only damages the upper 12-14 inches of the grain mass, removal of the webbing and damaged grain along with an application of a labeled insecticide are recommended. Pest strips hung above the grain mass inside the storage structure may help control the moth stage of this common pest. If an infestation of various flour beetles, grain weevils, or other stored grain beetles is found infesting the cold grain mass, then use of grain for livestock feed or some other use where the insects do not cause a problem in the end product is recommended. The grain should be fed to livestock prior to the arrival of summer temperatures when insect activity increases. If the grain is to be retained into the summer, then fumigation of the entire grain mass is a second, but less attractive management option. If fumigation is selected, a professional fumigator should be used as the poisonous gases associated with fumigation are extremely dangerous if used improperly. A third option would be to move the grain out of the storage facility to another storage structure with the grain being treated with a recommended insecticide as the grain is moved. When the grain is then warmed in the spring, the insecticide should provide substantial insect control. Of these three options, immediately use of the grain as livestock feed is generally the best option. Once the grain in removed from the bin, sanitation procedures should be implemented and the bin treated with an approved insecticide both inside and out.

All insecticides for stored grain insects have very specific labeled uses so special attention must be given when selecting an insecticide for these various uses. Some insecticides are label for use in empty grain bins, but are not labeled for use on grain. Some insecticides are labeled for wheat only or corn only, whereas others may be labeled for both. Be sure to read and follow all insecticide label instructions, restrictions, and precautions when using insecticides for management of stored grain insect pests.

Moisture in the grain mass is one very important factor which attracts insect pests to these structures. Charles Ellis, regional extension engineering specialist with the University of Missouri discussed the aeration and moisture zones in onfarm grain storage facilities in the January 15, 2009 issue of this newsletter (Volume 19, Number 1). Proper aeration of the grain mass to manage moisture and grain mass temperature is essential for good insect control. Note: it often requires a week or more of aeration to move a moisture layer through and out of a grain mass depending on several factors including the volume of air moved, the size of the storage structure, and the temperature of the air being moved into or out of the grain mass. A second article discussing moisture management in grain bins comes from Tom Dorn, a county extension educator associated with the University of Nebraska. His article can be found at http://cropwatch.unl.edu/web/cropwatch/archive?articleID=345002.

Color images and additional information concerning proper management of common stored grain insects can be found on the Commercial AG Electronic Bulletin Board at agebb.missouri.edu/storage/pests/insect.htm.