Insect Management Recommendations for "On Farm Stored Grain"

Wayne Bailey
State Extension Entomologist
University of Missouri - Columbia

Insect Management Recommendations for "On Farm Stored Grain"

Insect problems in stored grain are best prevented through sound grain management at the on-farm level. Implementation of sanitation practices which reduce residual pest insect numbers in empty bins and grain handling equipment coupled with pre-harvest insecticide applications to empty bin surfaces and surrounding areas is the first step in effective management of insect pests in stored grain. The second step is to apply a grain protectant on the grain to be stored. This application is essential if the grain will be in storage through the summer months or longer the following year. The grain is generally treated with a labeled insecticide as the grain stream is moved into the storage structure. This is followed by a second insecticide application to the top of the leveled grain mass inside the bin or structure. This (capping) treatment prevents insect from infesting the grain through the top of the grain mass. The third step is to monitor stored grain on a specific schedule to determine if insect infestations are present. Grain held through the winter into the following summer months is at high risk of developing insect infestations if not treated during filling of the storage structure. Due to high oil content of soybean, insect problems during storage of this crop are minimal if grain moisture is maintained at 13 - 14%.

If grain bins and handling equipment are not sanitized prior to grain fill and grain is moved into storage without receiving a preventative insecticide application, then insect infestations can develop in as little as 3 to 6 weeks following initiation of grain storage. In normal years cool fall temperatures usually allow the stored grain mass to be cooled to 50 - 55 degrees Fahrenheit which causes insects infesting the grain to become inactive. Some grain management recommendations suggest reducing the temperature of the grain mass to 35 - 40 degrees F to restrict the development of molds. Grain should not be frozen when reducing grain mass temperature in the fall. During periods of warm fall temperatures the risk of late season insect infestations of stored grain is increased. In the spring the grain mass should be warmed to a minimum of 60 degrees F to prevent condensation of moisture on bin walls and subsequently damage from insects and molds.

The high value of grain crops held in on-farm storage can best be protected by implementation of a monitoring program for detection of insect infestations and other pest problems within the storage structure. Producers should monitor stored grains regularly to assess grain moisture, temperature, and the presence of insect infestations.

The following summary includes a list of labeled insecticides, use rates and labeled uses. This information was revised 9/2014.

Steps to Successful Insect Management in Farm-stored Grains

    1. SANITATION. Thoroughly clean all grain residues from bins. Remove all residues from areas around the bins and nearby feed bunks or feed storage areas. Remove all grain residues from combines, trucks, and augers. Be sure to clean grain debris from fans and other grain handling equipment. These residues will be the main sources of insect infestations for farm stored grain. This is a very important part of a good grain management program and can prevent many stored grain insect problems.
    2. RESIDUAL SURFACE SPRAYS TO EMPTY BIN. After all debris and grain residues have been removed, an application of a residual insecticide should be made to the complete inside of the bin. This insecticide should also be applied around the exterior and to all areas where residues were removed. Spray all surfaces until wet; usually one gallon will cover 1,000 square feet prior to storing or handling grain. Use a course spray at a pressure of at least 30 psi. Insecticides are most effective if temperatures are 60F or higher.
      For optimal insect control labeled products should be applied to empty grain bins 6-8 weeks prior to filling bins with grain. If sprayed within a few days of grain fill the performance of the insecticides may be reduced. Insecticides labeled for empty bin surfaces include:
      1. Beta-Cyfluthrin Formulations: - for application to empty bin interior and exterior surfaces only, not to grain.

        Tempo 20WP see specific label

        Tempo 2EC see specific label

        Tempo SC Ultra - 0.27 to 0.54 fl oz per 1 gallon of Water

      2. Chlorpyrifos-methyl plus Deltamethrin: for application to empty bin interior and exterior surfaces only, not to grain.

        Storcide II - 1.8 fl oz per 1 gallon of water Warning-This insecticide should only be applied from outside the bin using automated spray equipment. Do not enter the bin until all sprays have dried.

      3. Deltamethrin: for application to empty bin interior and exterior surfaces only, not to grain.

        Suspend SC - Use 0.25 to 1.5 fl oz in enough water to cover 1000 square feet of area. See and follow specific label rates and directions.

      4. (S)- Methoprene: Interferes with insect development, but does not directly kill adult insects. For use in reducing insect numbers over an extended period of time.

        Diacon II and Diacon-D - see and follow specific label rates and directions.

      5. Silicon Dioxide, Diatomaceous Earth:

        Several brands including Dryacide, Insecto, Protect-It and others - Follow specific label directions.

      6. Malathion:

        Malathion - various formulations available, but not recommended for empty bin treatment due to lack of control of Indian meal moth and lesser grain borer. "Do not apply directly to grain".

    1. PROTECTANTS FOR APPLICATION TO GRAIN. If grain is to be held in storage into the summer months of the year following harvest or longer, then a grain protectant applied at harvest is recommended. Formulated sprays, drips or dust formulations are typically applied to moving grain stream as it goes into storage vessel.

      1. Chlorpyrifos-methyl + deltamethrin (Storcide II) - dilute labeled rate of Storcide II in 5 gallons of water and apply formulated spray into grain stream. Five gallons of formulated spray applied to 1,000 bushel of grain.

        Storcide II rates per 1,000 bushel of grain crop are as follows:

        Barley 9.9 fl oz per 1,000 bushels
        Oats 6.6 fl oz per 1,000 bushels
        Rice 9.3 fl oz per 1,000 bushels
        Sorghum 11.6 fl oz per 1,000 bushels
        Wheat 12.4 fl oz per 1,000 bushels

      2. Pirimiphos-methyl: labeled for corn including pop corn and grain sorghum.
      3. Actellic 5E - use 9.2 to 12.3 fl oz per 5 gallons of water per 30 tons of grain (approximately 1071 bu.). Note: labeled for corn and sorghum only.)

      4. (S) - Methoprene: Labeled for barley, corn, grain sorghum, oats, rice, and wheat.
      5. Diacon II and Diacon-D - see and follow specific label rates and directions

    2. SURFACE TREATMENTS OR TOPDRESSING AFTER BIN FILL IS COMPLETE. Fill bins only to height of side walls and level grain prior to applying surface or top-dress insecticide treatments to prevent invading insect infestations, especially Indian meal moth.
      1. Bacillus thuringiensis (Bt)
      2. Biobit HP and Several Dipel formulations including Dipel DF - 1 lb/ 10-20 gal/1,000 square feet. Most often used for Indian meal moth larval control. See label for specific instructions and target pests.

      3. Silicon dioxide, Diatomaceous earth
      4. Several formulations including Insecto at rate of 4 lbs/1,000 square feet or Protect-It at the rate of 40 lbs/1,000 square feet may be used if grain mass was not previously treated with this protectant. See label for specific instructions and target pests.

      5. Pirimiphos-methyl
      6. Actellic 5E-3.0 fl oz per 2 gallons of water per 1,000 square feet of grain surface. Note: Labeled for corn and sorghum only.

  4. Grain masses should be monitored a minimum of once each month during the winter months of November through April and at least twice per month during the summer months of May through October. Areas of the grain mass most frequently infested include the grain surface and central core. Special attention should be given to these areas when sampling, but other areas of the grain mass should not be ignored.

    Scouting methods differ by location in the bin and the specific type of insect present. To determine if insects are present, producers should visually inspect the top of the grain mass by looking through the roof access door. 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 indicate the presence of an insect infestation. If an insect infestation is found on the surface of the grain mass and webbing is present, this usually indicates the presence of Indian meal moth. 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 an appropriately labeled insecticide are recommended. Pest strips containing (dichlorvos or DDVP) hung above the grain mass inside the storage structure may help prevent Indian meal moth infestations by controlling the moths of this common pest as they enter the storage structure. If no insects, webbing or foul grain odors are found during the inspection, then it is unlikely that Indian meal moths are present in high numbers. If the grain was properly leveled and the grain surface treated (capped) with an insecticide after filling of the storage structure the previous fall, it is best not to break or disturb the protective cap of insecticide previously applied at that time. It is best not to enter or walk on the treated grain surface as insects may establish in the disturbed areas unless these area are retreated.

    Similarly, an inspection of grain from the interior of the grain mass is also needed. Monitoring of the grain mass is best achieved through the side access panel by using plastic tube traps, probe traps, and sticky pheromone traps. These traps are inserted into the grain mass for a certain period of time and then retrieved. These types of traps will attract insects and help determine the kind and number of insects present. If traps are unavailable, a quick but less accurate method of sampling the grain mass for insects can be accomplished by direct observation of grain removed from the side door using a grain probe. Deep probes should be collected from several locations in the bin with the collected grain placed in a quart 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. Although there are no reliable thresholds for most insects found in stored grains, it is usually considered that if insects are found in the 1 quart samples of collected grain, the grain content of the bin should be either quickly used before grain quality is diminished by insect activity or treated (fumigated) to kill insects present in the grain and prevent excess loss of grain quality when stored at summer temperatures.

  6. If infestations of various flour beetles, grain weevils, or other stored grain beetles are found infesting the cold grain mass, then the immediate use of grain for livestock feed or some other use where the insects do not cause problems 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. Producers can legally fumigate grain bins in Missouri providing they possess a valid private pesticide applicator license when purchasing and using the fumigants. However, due to the extreme hazard associated with the very poisonous gases emitted by the fumigation pesticides and the extreme danger if used improperly, it is strongly recommended that a professional fumigator be contracted to fumigate grain bins and other grain storage structures. A third option would be to move the grain out of the storage facility immediately after the grain has been warmed in the spring. The grain would be moved to another storage structure with the grain being treated with a recommended insecticide as the grain is moved. Be sure to consider whether the grain was previously treated with and insecticide when placed in the bin the prior fall to avoid excessive insecticide residues. This method of insecticide application should provide satisfactory insect control on a short term basis. Of these three options, immediate 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 empty bins treated with an approved insecticide both inside and out.

    1. GRAIN FUMICANTS. Recommend use of commercial pest control specialist when using grain fumigants for stored grain insect control. Special safety equipment including a self-contained breathing apparatus is required for this insecticide application.
      1. Aluminum Phosphide (phosphine gas - restricted use)
      2. Phostoxin, Fumiphos, Fumitoxin, Phoskill, Phosteck, Phosfume, Weevil-cide and other formulations. See specific labels for rates of pellet or tablet use.

All insecticides for stored grain insects have very specific labeled uses so special attention must be given when selecting an appropriate insecticide . Some insecticides are labeled 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.

Color images of common stored grain insects can be found on the Commercial AG Electronic Bulletin Board at (section below).

Wayne Bailey, 573-864-9905.

Principal Stored Grain Insects


  1. Granary weevils cannot fly. Eggs are placed inside whole kernels. Damage is caused by the larvae feeding in whole grain and the adults feeding in and on whole or broken grain.
  2. Saw-toothed grain beetles seldom fly but both the larvae and adults feed on cracked or broken grain, flour, meal, breakfast food, stock feed, candy, and dried fruit. The thorax, the body region behind the head, has saw-toothed points on both sides.
  3. Larvae and adults of the red flour beetle and a closely related species, the confused flour beetle, feed on flour, grain dust, and broken grains.
  4. Larger cabinet beetles and several closely related species are general feeders on grain and grain products. They will also feed on material of animal origin, such as hides.
  5. The eggs of the lesser grain borer are placed on kernels and the larvae bore into the kernels. The adults can fly and also feed on grain.
  6. Rice weevil adults can fly. Eggs are laid inside the kernel. The larvae feed in whole grain while the adults will feed both in and on grain.
  7. Indian-meal moth larvae spin webs on the surface of grain and feed on kernels enclosed within the webbing. The larvae will also spin webs on sacked grain in storage areas.
  8. Cadelle larvae and adults feed on whole grain. The larvae bore holes in the wood within bins where they hibernate. This is one of the largest stored grain insects.
  9. Flat grain beetles are one of the smallest common stored grain insects. It Is usually found associated with out-of-condition or insect damaged grain.
  10. Angoumois grain moth eggs are laid on the outside of the grain. The larvae bore into the grain and feed within the kernel. Adults may fly from granaries and infest corn in the field.

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