Managing stored grain to minimize storage losses
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When grain harvest approaches, it’s important to review basic on-farm storage principles to maintain the quality of stored grain.
During harvest, prepare storage structures to receive grain, which includes practices to help prevent pest infestations. To maximize grain quality, use appropriate production and harvest practices as well as properly maintain and use grain handling equipment, drying systems and storage structures.
Here, we outline the four steps to maintain post-harvest quality and protect stored grains from insects, weather, rodents, self-heating, molds, mycotoxins and pesticide residues.
Step 1: Sanitize the bin and surrounding areas
Be sure the storage structure as well as any grain-handling equipment (conveyors, wagons, trucks, elevators) are free of leftover grain. Cleanup is most effective when completed in early spring or immediately after emptying bins.
Unnecessary grain residue present during early summer only allows insect infestations to increase as temperatures warm. Even small amounts of moldy or insect-infested grain left in the equipment can contaminate a bin of new grain.
You can simultaneously complete repairs such as sealing cracks and holes. When moving old grain to different storage, screen and, if infested, treat it by fumigating.
In addition to cleaning the bin, always keep the surrounding areas clean. This includes the outside area around the bin, beneath the floor and inside the ducts.
Debris and grain spills outside the bin encourage rodents and insects, which can then move in through openings. Prevent weeds from growing around bin areas, as these are ideal sites for pests to hide.
Inside the bin, sweep or vacuum grain dust and old grain from floors, walls and ceilings, which provide hiding places for stored grain insects. Here’s a common rule-of-thumb: If you can tell what has previously been in the bin, it’s not clean.
If you cannot easily remove the bin’s perforated floor and had insect infestations last season, consider hiring a professional pest control operator to fumigate the empty bin before filling it with new grain.
Roof leaks commonly lead to columns of spoiled grain. Check for these leaks by looking for light coming into the bin. Moisture coming into the bin through the seal between the bin and concrete will cause spoilage around the perimeter of the bin at the base.
Check the seal because sealants do deteriorate. Water will run away from the seal at the base of the bin wall if the concrete is sloped away from the bin. Also check the seals around the doors and hatches.
After cleaning and repairing, use a residual bin spray to treat the insect surfaces of the bins at least two weeks prior to filling (see Table 1).
It’s better to treat during the warmer months when insects are active. If you applied treatments more than three months earlier, apply an additional treatment two to three weeks before placing new grain in the bin.
When using residual bin sprays, clean, sweep and spray all bins before harvest. Do not add grain to a treated bin for at least 24 hours or until the walls have thoroughly dried.
Insecticides are registered for use in Minnesota to protect stored grain from insects, and were updated in April 2018. Active ingredient(s) are noted in parentheses
Table 1: Guide to residual bin sprays
|Centynal Suspend Polyzone (deltamethrin)||Controls a wide range of pests. Treat the inside of clean bins prior to storing grain. Can be used in outdoor perimeter applications around bins and on surrounding vegetation.|
|Diacon IGR, Diacon-D IGR ((S)-methoprene)||Active ingredient is an insect growth regulator that prevents larvae from developing into adults. Adult insects are not controlled. Can be tank-mixed with an adulticide such as Centanyl.|
|malathion||May not provide control of Indianmeal moth. Read label for usage directions. Do not apply directly to grain.|
|Tempo SC Ultra (cyfluthrin)||Check product label for rates. Do not apply directly to grain.|
|Storcide II (chlorpyrifos-methyl + deltamethrin)||Combines the active ingredients of Centynal (deltamethrin) with chlorpyrifos-methyl. Only apply it to empty storage bins using automated equipment.|
|Diacon IGR Plus (deltamethrin + S-methoprene)||Combination insect growth regulator and adulticide. Controls a wide range of pests; treat inside of clean bins prior to storing grain. Can be used in outdoor perimeter applications around bins and on surrounding vegetation.|
Step 2: Combine and load grain into storage
Run grain harvested with a clean and properly adjusted combine through a grain cleaner to further remove the fine materials which insects can feed on. You can also run grain with many broken kernels through a cleaner, but this will lead to additional weight loss.
Clean, whole grain helps manage insects, but it’s also important for properly aerating the grain mass during drying and storage. If fine materials aren’t present, air drawn into the grain from outside the bin will move more uniformly through the mass.
A grain distributor uniformly spreads fine material across the grain mass, and is extremely helpful in preventing fine material aggregations.
If you don’t use a distributor, the fine material will concentrate in a column at the center of the grain mass. Because this column is more dense, air will move around it through the less-dense grain mass, allowing moisture to build up in the center of the bin. Moisture buildup is the first step in grain quality deterioration.
Loading refers to creating a grain mass with several basic properties that ease handling and lead to long life.
The grain mass should be clean and dry, uniform without foreign material and stored in an aerated weatherproof structure. In addition, if you’ll be holding grain in storage for a year or more, use a grain protectant (see Table 2, in the “Protecting the grain” section below) to protect against stored grain insects.
Specific practices that help approach the ideal grain mass include:
Use slow drying methods to limit kernel damage.
Limit the number of times grain must be handled.
Operate augers and elevators at capacity and at the slowest possible speeds.
Store grain in aerated structures.
If you’re going to apply insecticide protectants to the grain, treat the grain stream just before it reaches final storage (Tables 2 and 3). Grain that’s treated and then transferred long distances through numerous grain handling systems – such as pneumatic systems, belt augers, conveyors, spouts, legs, etc. – before storage will have less insecticide residue when the grain is finally loaded into the bin.
It’s very important to note that, when grain drying is necessary, apply an insecticide protectant after the grain goes through the drier and has cooled. Commercial grain dryers generate enough heat to rapidly degrade insecticides applied to grain prior to the drying process.
Use grain protectants as you auger grain into the bin. Insecticides are registered for use in Minnesota to protect stored grain from insects, and were updated in April 2018.
Table 2: Grain protectants by crop
|Barley, corn, oats, rye, sorghum, wheat||Centynal EC, Suspend SC (deltamethrin)||Broad spectrum insecticide for control of many stored product pests. Apply as grain enters storage. Can be used for treating seeds.|
|All grains, any food commodity||Diacon IGR, Diacon-D IGR ((S)-methoprene)||Active ingredient is an insect growth regulator that prevents larvae from developing into adults. Adult insects are not controlled. Can be tank-mixed with an adulticide. Soybeans are not on the label; Canola, sunflower and legumes are on label.|
|Barley, corn, oats, rye, sorghum, wheat||malathion||May not provide control of Indianmeal moth. Do not use products not specifically labeled for application to stored grain.|
|Barley, oats, sorghum, wheat||Storcide II (chlorpyrifos-methyl + deltamethrin)||Combines the active ingredients of Centynal (deltamethrin) with chlorpyrifos-methyl. Apply as grain enters storage. Can be used for treating seeds. Not labeled for corn.|
|Barley, corn, oats, rye, sorghum, wheat||Diacon IGR Plus (deltamethrin + S-methoprene)||Combination insect growth regulator and adulticide. Protects stored grains and seeds against damage from Indianmeal moth, saw-toothed grain beetle, red flour beetle, confused flour beetle, rice weevil, maize weevil and other listed pests. Long residual control, reduces rebound of infestations.|
This is an alternative to treating the entire grain mass. Insecticides are registered for use in Minnesota to protect stored grain from insects, and were updated in April 2018.
Table 3: Layer treatments when filling the bin, by crop
|Grains, soybean, sunflower||Dipel DF (Bacillus thuringiensis ssp. kurstaki)||For Indianmeal moth larvae only. Apply into the grain stream as the last 4-inch layer is augured into the bin. This will not control Indianmeal moth adults or beetles.|
|All grains||Dryacide 100 Insecto (diatomaceous earth)||Treat the top 2 to 3 feet as grain is augured into the bin.|
Immediately after filling the bin and leveling the grain, apply a surface treatment (“top dressing”) of an approved grain protectant (Table 4). The surface treatment helps control insects that enter the grain through roof openings.
Surface treatments alone generally will not keep the grain insect-free, but they can reduce insect populations during the storage period. Surface treatments are effective if the following limitations are understood:
Surface treatment will not control an established insect infestation already in stored grain.
The surface treatment should not be disturbed, since it provides the protective barrier against insect infestations.
Apply insecticide to surface after grain is binned. Note: To ensure maximum control, remove all surface crusting and webbing prior to treatment. Insecticides are registered for use in Minnesota to protect stored grain from insects, and were updated in April 2018.
Table 4: Top-dressed surface treatment, by crop
|All grains, any food commodity||All grains, any food commodity Diacon IGR Diacon-D IGR ((S)-methoprene)||Active ingredient is an insect growth regulator that prevents larvae from developing into adults. Does not control adult insects.|
|Grains, soybean, sunflower||Dipel DF (Bacillus thuringiensis ssp. kurstaki)||For Indianmeal moth larvae only. As a surface treatment, apply a 1/2 pound of DiPel in 5 to 10 gallons of water per 500 square feet of grain surface. Mix into the top 4 inches.|
|All grains||Dryacide 100 Insecto (diatomaceous earth)||Apply 2-3 pounds per 1,000 square feet. For best results, use a surface treatment in combination with a layer treatment.|
Step 3: Aerate the grain
In the fall, aerate to cool the stored grain and create a better storage environment in bins with capacities greater than 2,000 to 3,000 bushels.
Keep grain temperature less than 50 degrees at all times of the year. In the upper Midwest, aerate to cool grain to 20 to 30 degrees for winter storage.
You should be able to cool grain to temperatures below 50 degrees Fahrenheit by gradually cooling the grain throughout the fall. Insect activity reduces at this temperature.
Minnesota temperatures allow you to achieve a target stored grain temperature of 25 degrees in the winter. At this temperature, insect activity ceases and some mortality will occur for a number of stored insect pests.
Make sure to cool and uniformly dry the grain mass. Move the cooling front completely through and out of the grain mass and maintain low grain temperatures as long as possible during storage.
It’s not necessary to rewarm dry grain with fans during the spring and summer.
Table 5 summarizes the recommended moisture levels for various grains for short- and long-term storage.
Table 5: Maximum recommended moisture content for grain storage with aeration (percent wet basis for clean, aerated grain crops)
|Crop||Up to six months in storage||More than six months in storage|
Step 4: Monitor stored grain
Regularly check stored grain for temperature, moisture, insects and molds.
Inspect stored grain every seven to 14 days when either outdoor or grain temperatures are greater than about 50 degrees Fahrenheit. For grain in good condition that’s been cooled to less than 30 degrees, you can increase the inspection interval to once every three to four weeks during cold weather.
Check for insects by screening them from the grain, examining kernels for damage, looking for webbing, detecting off-odors or monitoring grain temperatures. Insect infestations can raise grain temperatures to as high as 110 degrees Fahrenheit.
During the summer and fall, insect infestations are usually near the grain’s surface. During cold weather, stored grain insects congregate at the center and lower portions of the grain mass and may escape detection until extensive heating has developed.
The following tables show the relationship between grain moisture, storage temperature and storage time:
Reviewed in 2018