On-Farm Stored Grain Management: Insect Management for Farm-Stored Grain

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| Insects and Pests of Field Crops | Diseases of Field Crops | Appendices |

Pub 811: Agronomy Guide >On-Farm Stored Grain Management > Insect Management for Farm-Stored Grain

Excerpt from Agronomy Guide for Field Crops
Order OMAFRA Publication 811: Agronomy Guide for Field Crops

The key to controlling insects in stored grain is good sanitation and storage practices.

The following strategies are essential for preventing infestations, reducing the need for rescue fumigation treatments.

Keep a Sanitary Facility

The most important strategy is to keep the facility insect free by cleaning bins and equipment before storing grain. Grain residues from previous crops are the main source of new infestations. At least 2 weeks before filling bins, ensure the facility is thoroughly cleaned and pest free by removing all grain residue, as well as caked material, using a good vacuum cleaner. Ensure that all old grain has been removed from cracks and crevices, behind partitions, between double walls, outside and under bins, in grain-handling equipment, inside aeration piping and under perforated floors. Harvesting and grain handling equipment containing old crop residues are a very important source of new infestations. Fully perforated floors present a problem because they cannot be easily lifted for cleaning, and grain dust will accumulate and may become infested with grain storage pests.

Clean up all spills of grain and feed around handling and storage facilities. Burn all grain that is removed, deposit it in a sanitary fill or grind it up for feed. Leave space between feed rooms and storage facilities, because feed rooms are difficult to keep free of pests. Once established, storage pests can quickly spread to nearby storage facilities.

Do not store grain in buildings that shelter animals or hay. Mangers, feed boxes and troughs are often infested with insects. These shelters are also warmer and provide an excellent wintering site for insects.

Maintain Sound Storage Facilities

After clean-up, repair facilities so that they are pest-proof. Seal cracks and crevices that may allow insects to enter.

Store Clean, Dry Grain

Never store new grain with old grain, because insects will spread from the old grain to the new. Ensure that grain being placed in the storage facility is pest-free. Moulds as well as insects are much more troublesome in moist grain. If stored grain has more than 15% moisture, check it regularly. Wheat should be dried down to 12% moisture if you are planning to store it for longer than a month through the warm summer months. Corn should be dried to 14% moisture.

Monitor Storage Temperature and Sample for Insects

Wheat is the crop most susceptible to infestations because it is harvested during the summer when insects are most active inside and outside the storage facilities. Once in the bin, the grain is still warm and can provide an excellent habitat for stored-grain insects. In Ontario, corn storage usually follows wheat storage, and infestations can easily be carried from the wheat to the corn. Monitor the temperature of the grain using temperature sensors placed throughout the grain pile. Warm areas in the pile often indicate insect and/or spoilage problems.

Using aeration to cool down grain in the fall will reduce insect infestation and slow reproduction. Insects do not develop in grain with temperatures below 10°C and can be killed if temperatures are kept below -10°C for over 10 days. Rusty grain beetle and Indian meal moth can be monitored using plastic probe traps (see Plate 34). These probe traps are very sensitive and will show an infestation well before it reaches the economic threshold. If rusty grain beetle or Indian meal moths are found, fumigate the grain.

Plate 34. Insect probe for stored grain is inserted into grain to trap insects.

Treat Empty Bins With Diatomaceous Earth

Diatomaceous earth is a non-toxic dust made from a silicone-dioxide mixture from prehistoric, marine diatoms. When in contact with insects, the diatomaceous earth absorbs the protective waxy coating on the insect, causing it to die from dehydration. Apply the product to the empty bin through aeration fans at least 2 weeks prior to grain storage. Apply it to the grain as well, as it is being augured into the bin or storage facility. Wear a protective mask when applying diatomaceous earth to avoid inhaling the dust. See OMAFRA Publication 812, Field Crop Protection Guide, for detailed application and label information.

Do not exceed application rates when treating grain, as this will result in auger plugging problems.

Preventative insecticides are not a substitute for good storage sanitation practices.

If bin surfaces are dusty or covered with caked material, control products may not penetrate to kill crawling insects. Malathion is no longer recommended for Indian meal moth control as this insect has acquired resistance and is frequently not controlled by this product.

Use Rescue Treatments When Necessary

Should an insect problem occur, fumigation might be necessary. Turning the grain may reduce a secondary pest problem to below economic damage. However, if rusty grain beetles or Indian meal moths are evident, the problem is serious. If webbing is found on the surface of the pile, rake and remove this layer before fumigating. For information on fumigants, see OMAFRA Publication 812, Field Crop Protection Guide. Grain must be above freezing temperatures for all fumigants to work properly. Because of this fact, fumigation may not always be possible when desired. Fumigants may only be applied by a licensed exterminator. Remove livestock and poultry that are in the same building, especially if they are under the grain bin.

Identify Pests Properly

Stored-grain insects are not specific to one crop but can move and feed across commodities. It is important to know which insect pest you have in your facility. Proper identification and pest density assessment are important, because management strategies may differ, depending on the pest. Proper identification will also help determine the source of infestation. Some insects are only incidental pests and may not cause economic loss.