Stored grain pests


Almond moth (Ephestia cautella)
Angoumois grain moth (Sitotroga cerealella)
Flour beetle (Tribolium spp.)
Granary weevil (Sitophilus granaries)
Indian meal moth (Plodia interpunctella)
Maize weevil (Sitophilus zeamais)
Rice weevil (Sitophilus oryzae)
Saw-toothed grain beetle (Oryzaephilus surinamensis)

Storing grain properly

Store only clean, dry grain containing less than 12 percent moisture. Grain mixed with green weed seeds, broken kernels, or dirt provides conditions favorable for insect development.

Aerate grain

Moisture condensation can develop in storage bins when unequal temperatures in the grain mass cause gradual circulation of air from the warm to the cold grain. As air passes through the warm center of the grain, small convection currents pick up moisture and deposit it in the cold areas. This can result in spoiled, crusted grain on the surface, in the middle of the bin, on top-center, or along the outside.

To prevent condensation, aeration is needed to keep the grain within 15°F of the average outside temperature. Start aeration fans shortly after harvest, and run them periodically until November. In the spring, aeration should be used to raise the temperature of the grain to about 50°F.

Inspect grain

Inspect stored grain once a month. You can detect infestations using a grain probe or by hand. Areas that are hot generally indicate an infestation. Watch especially for signs of crusting near the top-center and outside edges. You might see live insects and damaged kernels on the surface, especially at the crown. Surprisingly, large populations of these pests can develop by mid-winter. Light traps, pheromone kits, and other types of traps are available for collecting, detecting, and monitoring many pests.


Good housekeeping and rapid inventory liquidation are key to preventing infestations. Before harvest and grain storage: (1) remove grain, or else treat grain that is to remain in storage. Grain stored over 9 months is susceptible to infestation; (2) thoroughly clean with industrial vacuum the storage warehouse, floors, walls, ceilings, cracks and crevices, and all equipment. The most common source of an insect infestation for newly stored grain is old grain residue which is everywhere: in and on trucks, trailers, combines, dump pits, bins, augers, and virtually anywhere that grain passes or is stored. Infestations may be introduced on pallets or in contaminated or infested bags of grain or seed, even though these may appear to be clean. Pelleted livestock feed, dry animal foods, feathers, and old hides may also harbor the pests that infest stored grain.


Insecticides are highly recommended for treating the interior walls and floor. Malathion products, Tempo Ultra SC and Tempo 20WP (cyfluthrin), and Storcide II (chlorpyrifos-methyl+deltamethrin) are registered for surface treatments. Apply according to label instructions. Bin wall and floor treatments should be made at least 1 week prior to filling. Note: No international level of tolerance has been established for cyfluthrin. Grain treated with this product may not be accepted in international markets. Avoid contaminating storage areas where exported grains may be stored. Caution-Some buyers will not accept insecticide-treated grain. Check with your local elevator before treating.

Grain to be stored 9 months or longer is often treated for protection against beetles and moths when augured into storage. The possibility exists for rapid infestation as the protectant breaks down; storage longer than 18 months is not recommended. Protectants are added to the grain as it is unloaded, or as it enters the bin for final storage. To be effective, protectants must be mixed thoroughly with the grain. If subsequent surface infestations are detected, try to determine the reason (e.g., a leaky roof leading to moistening of the grain) and correct the root cause. Minor infestations can be treated by incorporating a registered product into the top 8 to 10 inches of grain.

Management-chemical control

Direct grain treatments

  • Bacillus thuringiensis kurstaki (Biobit HP) at 0.5 lb in 5 to 10 gal of water per 500 sq ft of grain surface area, mix into top 4 inches for Indian meal moth, Angoumois grain moth, and almond moth. Mix with grain when placed in storage and/or periodically apply to surface of stored grain; see labels. Biobit HP is OMRI-listed for organic use.
  • chlorpyrifos methyl/deltamethrin (Storcide II) at 5 gal of water final spray per 1,000 bu of grain. See manufacturer's recommendations for use with food-grade oil. Apply 3 ppm chlorpyrifos and 0.5 ppm deltamethtrin to a moving grain stream headed for storage. Product rate per 1,000 bu is 12.4 fl oz for wheat, 9.9 fl oz for barley, and 6.6 fl oz for oats. Not labeled for corn.
  • malathion dust admixture (Max Kill Dusta-Cide) at 0.6 lb ai per 1,000 bu, applied as grain is loaded or turned into final storage.
  • malathion dust top dressing (Max Kill Dusta-Cide) at 0.3 lb ai/1,000 sq ft of grain surface. For Indian meal moth control. Limit 3 treatments of malathion product.
  • methoprene (Diacon IGR) top dressing at 1 ml in water or food-grade oil per 1,000 sq ft of grain surface.
  • methoprene (Diacon IGR) admixture at no more than 4.4 oz ai in 5 gal water or food-grade oil per 1,000 bu. Apply to the moving grain stream. Methoprene does not kill adult insects, but does prevent reproduction.
  • methoprene/deltamethrin (Diacon IGR Plus) apply in 3 to 5 gal water or food based oil at label rates per 1,000 bu of grain.
  • pirimiphos-methyl (Actellic 5E) admixture at 0.36 to 0.48 lb ai in 3 to 5 gal water or food-grade soybean oil to each 30 tons of commodity. Corn only.
  • pirimiphos-methyl (Actellic 5E) top dressing at 0.12 lb ai in 2 gal water to each 1,000 sq ft of grain surface. Not labeled for wheat. Extreme heat results in volatilization and reduction in residual control. Corn only.
  • pyrethrins/synergist (Pyrenone Crop Spray) as admixture in a 1.7% pyrethrin solution. Apply 4 to 5 gal per 1,000 bu of grain, applied as conveyed along belt or when entering the auger or elevator. Primarily for Indian meal moth control.
  • pyrethrins/synergist (Pyrenone Crop Spray, TurboCide Gold) as top-dressing in a 3.3% pyrethrin solution. Apply 1 to 2 gal/1,000 sq ft of grain surface. Rake into grain to 4 inches.
  • pyrethrins/synergist (Py-75) as a space spray per 1,000 cu ft. Rates vary; check label.
  • silicon dioxide from diatomaceous earth (Perma-Guard) at 7 lb powder directly onto each ton of grain. Mix thoroughly. Perma-Guard is OMRI-listed for organic use.
  • spinosad (Sensat) admixture at 1 ppm delivered to 1 ton of grain.
  • spinosad (Sensat) top dressing mix 2.6 fl oz in 2 gal water per 1,000 sq ft of surface. Sensat label is not listed for organic use.

Storage building-residual spray or space treatment

  • beta-cyfluthrin (Tempo SC Ultra) at 0.034 to 0.067 oz ai (8 to 16 ml)/1,000 sq ft as surface spray. No international level of tolerance has been established for cyfluthrin. Grain treated with this product may not be accepted in international markets. Avoid contaminating storage areas where exported grains may be stored.
  • chlorpyrifos methyl/deltamethrin (Storcide II) at 0.4/0.07 oz ai (1.8 fl oz) in 1 gal water for treating empty grain bins. Apply 1 gal/1,000 sq ft. Bin and warehouse applications should only be applied from outside the structure. Use of automated spray equipment is mandatory when applying to empty bins. Not labeled for corn.
  • cyfluthrin (Cy-Kick CS) at 0.05% to 0.1% spray formulated product. May be used to treat grain storage facilities. Do not apply to grain.
  • cyfluthrin (Tempo 1% Dust). Apply as a crack and crevice treatment in grainaries. Do not apply to grain.
  • ddvp (Max Kill Vapocide, Nuvan Aerosol)-Apply as a fog or ULV spray at 1 to 2 grams per 1,000 cu ft.
  • deltamethrin (Suspend SC) at 0.08 to 0.5 lb ai per 100 gal final spray in grain bins and warehouses. Apply to surfaces at 1 gal per 1,000 sq ft.
  • esfenvalerate/pyrethrins (MGK Shockwave) as contact spray or thermal fog in granaries, mills, elevators and other areas. Consult label. RTU for use in mechanical sprayers which generate aerosols.
  • fenvalerate (Onslaught) at 0.025 to 0.05% (0.5 fl oz to 1 fl oz) per 1000 sq ft. Apply to cracks, crevices and other surfaces. Retreatment interval 14 days. Do not apply to grain.
  • lambda-cyhalothrin (Demand CS) at 0.015 to 0.03% (0.2 to 0.4 fl oz/gal) as surface spray.
  • malathion (Loveland Malathion 57EC) at 0.6 lb ai in 3 gal water and apply on 1,000 sq ft to grain storage facilities. Do not apply to grain.
  • methoprene (Diacon IGR) may be used as a fogging concentrate. Methoprene does not kill adult insects, but rather prevents reproduction.
  • pyrethrins/synergist (Py-75, Pyrocide 100, TurboCide Gold) as a contact spray per 1,000 sq ft and followed as a space spray per 1,000 cu ft. Rates vary; check label.
  • tetradecadien acetate (Cidetrak IMM) as a space spray. Do not exceed 200 grams ai per 7063 cu ft per year.