As many of you are beginning to drain fields in preparation for harvest, this is a good time to think about proper bin preparation to prevent insect infestation of stored rice. Recently, we have had reports of Angoumois grain moth (Figure 1) infesting rice that was being cleared out to make room for the new crop. This infestation further emphasizes the importance of proper grain (ensuring correct moisture content) and bin preparation. In order to prevent infestation of your storage bins, we recommend taking a few preventive steps.
To begin, be sure to thoroughly clean the storage bin. Good sanitation may prevent infestation of stored grain and decrease cost by preventing the need for fumigants. Both old and new bins should be prepared in the same manner. The bins should be thoroughly cleaned at least 2 weeks prior to storing grain. To properly clean bins, all old grain, trash and debris should be removed from within the storage bin and fumigated or burned. Brush away all debris (including spider webs) attached to the sides of the bin and wash the inside and outside surfaces of the bin with a high-pressure hose. Be sure to remove all grain from cracks and crevices. Any grain left in the cracks can increase your chance of infestation by stored-grain pests.
After the bin is clean, it should be treated with an insecticide. Spray the bin inside and out (including overhead) with a labeled insecticide. Treat the wall surfaces and any cracks and crevices. Be sure to follow all label instructions when applying any insecticides. The pH of the tank water should be adjusted using a buffering adjuvant as necessary. For best results, the tank water should be slightly basic with a ph of 5.5 to 6.5. There are two insecticides labeled for use in storage bins that will contain rice. These include: 1) Tempo SC Ultra (20% cyfluthrin): apply 8-16 mL of concentrate per 1,000 square feet of bin surface (see label for the amount of water to add in preparing the spray solution) and 2) Storicide II (21.6% chlorpyrifos-methyl and 3.7% deltamethrin): mix 1.8 fluid oz. per gallon water per 1,000 sq. ft. of bin surface.
You may want to consider applying a grain protectant to rice which will be stored. This action may prevent early infestation of stored grain. Grain must be at the proper moisture content for storage prior to application. DO NOT apply the grain protectant before high-temperature drying. Insecticides labeled for treating rice include Storicide II: mix 9.3 fluid oz. per 5 gallons water per 1,000 bushels. If rice is already infested with a grain pest (at the time of harvest), it must be fumigated before storage.
If your rice becomes infested with a stored-grain pest while it is being stored in a bin, fumigation is the only option of treatment. The only fumigant registered for use in stored rice is aluminum phosphide (Phostoxin). Be sure to follow label instructions for application method, rate and insects to treat. The bin must be closed a minimum of 4 days during fumigation.