Grain harvest is fast approaching and given our current market situation, it is likely that this will be another year when grain storage will be an important piece of a grain marketing strategy. It is likely that some grain bins have only recently been emptied in preparation for this year’s harvest and that is just the first step in good grain bin preparation. This week I am using an article written by Lee Townsend, Extension Entomologist from the University of Kentucky, plus a section on specific insecticide products from an article written in September of 2015 by Curtis Young, OSU Extension Educator in Van Wert County.
The primary causes of grain spoilage during storage are excess moisture and high temperature. However, insects can infest any grain that is not handled properly or that is stored longer than 6 months. Damage from weevils or other stored grain insects can be costly. Unfortunately, they often are discovered when grain is being taken out of the bin. At that point, the damage has been done and there are few control options.
The elements of pest prevention, the key to successful long-term storage are sanitation, protection, and inspection. Arguably, sanitation is the key because infestations of stored grain insects rarely begin in the field. They usually develop from small numbers of pests present in or around farm storage bins or in grain handling equipment. An effective sanitation program can greatly reduce the chance of having serious problems with these insects.
Harvesting should begin with empty, clean bins. Never put newly harvested grain into bins containing old grain. Remove any residual grain as thoroughly as possible using shovels, brooms and an industrial vacuum. Clear dust, webbing and fines from around any cracks and crevices, doors, seams, and vents. Inspect clean bins and repair any cracks or holes that could allow moisture or insects to enter. Then, spray the inside of the clean, empty bins completely with a labeled residual insecticide. Apply a coarse spray to run-off at least 2 weeks before binning. Pay close attention to areas that might hide insects, such as under perforated floors and vents. Cracks around doors and vents may serve as entryways.
Registered empty-bin insecticides include: Tempo SC Ultra (cyfluthrin), Storcide II (chlorpyrifos-methyl plus deltamethrin) which is primarily used around small grains such as wheat, Centynal or Suspend SC (deltamethrin), Diacon-D IGR (s-methoprene = an insect growth regulator), and several pyrethrin products can be used to apply a surface treatment to the inside of the bin and provide a residual protection. Other products that contain diatomaceous earth and/or silicon dioxide such as Insecto, Protect-It, Perma-Guard and others may be utilized. Refer to the individual product labels for lists of insects controlled and application directions. Note: most if not all malathion products have removed stored grain uses from their labels. Grain storage insecticide labels tend to change frequently. As always, check to make sure you are following the instructions on the product label and using the appropriate product for your situation.
If a bin is known to be heavily infested with insects, an empty-bin fumigation may be required to knock down insect populations before applying one of the above insecticides. The most readily available product for this purpose is phosphine gas producing materials such as aluminum phosphide and magnesium phosphide sold under a wide variety of trade names. Phosphine is an extremely toxic material and fumigations should be conducted by trained, experienced, licensed applicators.
Thorough preparation also should include the area immediately around the bins. Remove and destroy any spilled grain. Clip tall weeds and grasses that can harbor spilled grain, insects, and rodent pests. Inspect outside walls, especially the base and roof for damage that could allow pests and moisture to enter.
Put only clean, dry grain into the bins. Most stored grain insects require 13% to 15% moisture for maximum feeding and reproduction. Clean grain that is likely to be held for more than 6 months. This reduces the chances for problems with pests like bran beetles that live on fines and produce metabolic heat and moisture that reduces the stored grain's quality.
Level the grain surface after the bin is full. Good airflow allows improved moisture and temperature control and easier access for inspection. Regular grain bin inspection provides important information on the general condition, temperature, and moisture. Early detection of an insect infestation allows quick response to deal effectively with it.
See Controlling Insects in Stored Grain, https://entomology.ca.uky.edu/ef145 for more information.