You spend $25/acre or more to keep bugs from eating your corn and other crops. Bt tech fees, insecticide costs and application expenses don't come cheap. But don't forget about bug control when the crop is harvested.
On-farm storage can be a tidy home for numerous insects. It can be warm and moist and provide a 24-hour food supply once the crop is in.
“Field pests are important,” says Carl Patrick, Texas A&M extension entomologist in Amarillo. “But when the grain goes into storage, another set of insect problems should be of concern.
Putting grain into dirty bins and failure to properly aerate can create an environment crawling with granary weevils, saw-toothed grain beetles, Indian-meal moths and other grain-hungry creatures.
Wayne Bailey, University of Missouri extension entomologist in Columbia, says plans for farm-stored grain handling must begin long before harvest.
“Residue will be the main source of insect infestations for farm-stored grain,” says Bailey. “So it's important to thoroughly clean all grain residue from bins and from areas around bins and any nearby feed bunks or storage,” he says. “All residue must also be removed from combines, trucks and augers.”
Many growers with on-farm storage depend on grain cleaning and handling services to baby their grain in the bin. Camron Patten, whose service contracts with some 300 farmers and others as clients, says a thorough cleaning is a must.
“We recommend that bins be cleaned first, along with elevators and aeration tubes from top to bottom,” says Patten, who operates Kem-Tek out of Leoti, KS, with his father Doug. “Once cleaning is completed, then a bin is either treated with diatomaceous earth (DE) or sprayed with Tempo or other recommended products.”
DE is a common non-toxic, talc-like powder that has been used for insect control for literally thousands of years. It's an organic material consisting of the fossil remains of siliceous skeletons of diatoms, which are microscopic marine freshwater algae. The powder acts like finely ground glass that is easily picked up by hairy bodies of most insects.
Tom Phillips, an entomology professor who specializes in stored product entomology at Oklahoma State University, says DE is very effective in killing existing infestations. “When using it with corn, it's important to make sure the grain is below 15% moisture,” says Phillips. “Otherwise, it will lose its effectiveness.”
DE is applied at a rate of about 50 lbs./1,000 bu. The powder can reduce the test weight of grain by about 1 lb., and up to 3 lbs. for wheat. So it's best not used if grain is to be marketed in the near future. “If you know you will be storing grain into the summer months or longer, DE is recommended,” says Patten. “We've had grain in storage seven years with no insect problems.”
But because of the reduced test weight from DE, if grain is to be marketed before spring, Patten says fumigation could be the most cost-effective treatment.
Patrick says fumigation, usually using a phosphine gas, may be required if grain becomes infested. Phosphine is a restricted-use pesticide, so applicators must be certified for fumigation. A pesticide applicator license for general farm use may not be enough.
“The new label for phosphine products requires a fumigation management plan to be on file for the facility being treated,” says Phillips. “Documentation may be needed about when the chemical was applied, how much, if there was any gas leakage, etc.”
Areas of stored grain most frequently infested include the surface and the central core below the filling spout where fine material accumulates. Bailey advises growers to keep crusts from forming at the top of the grain pile to reduce potential insect damage.
Once grain is placed into storage, it should be aerated every two to three weeks for a 10,000-bu. bin. “On larger bins, up to 100,000 bu. in capacity, we recommend aeration every four to five weeks,” says Patten, “depending on the power of the aeration fans or the moisture of the grain going in the bin. Aeration and ventilation are the most important things for corn and soybeans.”
Phillips says a key to good fumigation is to only run fans when the outside temperature is lower than grain temperature. “Some people run fans day and night, and if the day temperature is warm, they're defeating the purpose,” says Phillips.
Aeration helps keep grain dry and at a steady temperature. “The temperature of the grain mass should be within 20°F of the average outside air temperature,” says Bailey.
Periodic inspections of stored grain are essential — preferably about once a month. Samples of grain should be taken from core areas and checked for insect damage, mold, moisture and other problems. Never mix new grain with old grain, and don't store new grain near old grain unless the old grain has been treated for insects.
Bin Treatment Options
University of Missouri Extension Entomologist Wayne Bailey says to be sure to spray all surfaces until wet when treating empty bins for insects. One gallon should cover about 1,000 sq. ft.
He points out several other labeled effective compounds for controlling insects in stored grain. They include:
Methoxychlor — A 2.5% solution made by mixing ¾ pt. of 25% methoxychlor emulsifiable concentrate per gallon of water.
Chlorpyrifos-methyl (Reldan 4E) — A solution made by mixing 4 fluid ounces of Reldan 4E in 3 gal. of water (not labeled for corn).
(RU) Cyfluthrin (Tempo 2 or Tempo 20WP) — Follow label instructions and mix a 0.05% active ingredient concentration. Restricted for pest control operators and commercial use.
Some insecticides may be applied to grain before, or as it is being elevated into the bin. “Insect populations are greatly reduced or prevented by using these materials,” says Bailey.
Pirimiphos-methyl (Actellic 5E) can be applied to grain. Dilute Actellic 5E with water per directions on the label and apply to the moving grain to give a deposit of 6-8 ppm on the grain. Actellic is labeled on corn and sorghum, but is not labeled on small grains.
“Surface treatments may be needed when bin fill is complete, when the grain is in condition for storage and when the grain surface is level,” says Bailey.
Insecticides labeled for surface applications are: malathion on corn, wheat, oats, rye, barley, sorghum and sunflowers; chlorpyrifos-methyl (Reldan) on wheat, oats, barley, rye, sorghum and sunflowers; pyrethrins plus piperonyl butoxide on corn, wheat, oats, barley, rye, sorghum and sunflower; Bacillus thuringiensis, a biological control compound, on corn, soybeans, wheat, oats, barley, rye, sorghum and sunflowers; and Pirimiphos-methyl (Actellic 5E) on corn and sorghum.