It’s Time To Clean Your Grain Bins (And Everywhere Else Around Your Grain Bins)

By Curtis Young

Late spring, summer and early fall are the times of the year that insects are most active, flying and walking around to disperse to new locations near and far, reproducing, building in populations and infesting new food resources. The stored grain infesting insects take advantage of these times of the year as well. With only a few exceptions, most of the store grain infesting insects can fly in the adult stage to move from location to location. If they find a food resource when they arrive at a new location, they can infest that food resource and begin building in population through the rest of the growing season. These food resources can include, but are not limited to stored grain still in grain bins from last year that has not been moved off the farm yet, empty grain bins with remnants of the last crop still in the bin, spilled grain, grain stuck in pits, augers, grain wagons, trucks and combines, wasted livestock feed, leftover seed that did not get planted this year, and grain stuck in empty feed and seed bags.  

As individuals finish moving last year’s and possibly older crops out of their on-farm storage, they may be surprised to find some serious insect infestations in their grain. It is preferred not to find any type of insect in our stored grain, but some are more significant than others. Many insects that are associated with stored grain are there to feed on broken grains, grain dust and molds that grow on these materials. These insects are classified as secondary pests of stored grains. Of much greater concern are those insects classified as primary pests of stored grains. These are the insects that attack sound grain (uncracked, unbroken, non-moldy grains) and make them unsound by boring into the grains. These primary insects are the grain weevils (snout beetles) and grain borers. Not only do they directly damage the grain, they are also very difficult to control.

With these facts in mind, now is the time to start prepping your grain bins for the harvest to come. If the grain bins are already empty, they need to be thoroughly cleaned on the inside and outside. The walls and the floors need to be swept clean. It would be best to use a shop vacuum to reach and remove all grain remnants that are tucked into cracks and crevices as well as the central feed out auger. Be sure to clean off ledges above hatch doors and if there is a ladder on the interior of the bin, be sure that hollow rungs are cleaned out. While working in the bin, look for holes and cracks to the outside are detected and fixed.

On the outside of the bins, clean up any spilled grain, remove or mow weeds from around the base of the bin, and if there is an aeration fan, check the plenum for any accumulation of grain and remove it.

Other areas that should be cleaned to remove any accumulations of grain include augers, grain pits, grain elevator belts, grain driers, grain carts and truck beds, and combines and combine heads. Grain accumulations in any of these pieces of equipment could have been infested during the summer months. The rule of thumb is, if you can look into any of these pieces of grain handling equipment and be able to tell what the last grain crop that was run through it, it is not clean enough.

If a bin has had a known insect problem in the recent past where a residual population of the insect(s) could be hidden under the perforated aeration floor, fumigation might be the only option to destroy these hidden insects.  The most likely product to be used for this purpose is aluminum phosphide (phosphine gas) which is sold under a number of different trade names such as Phostoxin, Fumitoxin and Weevil-Cide.  When determining the proper dosage for treating the empty bin, one has to remember that the dosage is based on the total volume of the area into which the fumigant is being released.

There are several precautions to be addressed when using aluminum phosphide as a fumigant:

1. The phosphine gas released by aluminum phosphide is only slightly heavier than air and will sink through a perforated aeration floor into the void below, however any air flow that is allowed to pass through the grain bin will easily carry off the phosphine gas from the intended target area.  Thus, to accomplish a successful fumigation of the volume of the targeted area within the bin, the area must be completed sealed!  If one is not willing to put forth the effort to properly seal the structure, don't use this product!
2. The entire empty bin does not need to be fumigated if the true target is below the perforated aeration floor.  Plastic sheeting sealed around the walls can be used to restrict the gas below the floor.
3. Phosphine gas is a highly toxic compound and must be handled with care following all safety requirements listed on the label and in the applicator's manual.  Phosphine gas is a colorless, odorless compound.  For safety purposes, the manufacturer of aluminum phosphide includes an indicator compound to warm persons of the potential presence of phosphine gas.  The indicator compound is described as smelling like, garlic, fish or carbide.  If a person smells this indicator compound, they should leave the area immediately.  Unfortunately, a person's sense of smell will become accustom to the odor very quickly and be undetectable.  Thus, absence of the odor does not mean safety.
4. The aluminum phosphide label and applicator's manual have gone through major revisions recently.  Thus, one must read both very closely to use this product correctly.
5. Once the fumigant is aerated out of the bin, there is no residual protection. Another insecticide would need to be applied to extend protection against re-infestation.

There are very few products left registered for use around and on stored grains.  Thus, the list is short.  For corn and popcorn bins, products registered for interior surfaces of empty storage bins include:

Tempo SC Ultra (active ingredient (a.i.) is cyfluthrin) used as a liquid spray

Centynal (a.i. is deltamethrin) used as a liquid spray

Pyronyl (a.i. is pyrethrin) used as a liquid spray

Diacon-D IGR (a.i. is s-methoprene) used as a dust application

Insecto (a.i. is diatomaceous earth) used as a dust application

For soybean bins, products registered for interior surfaces of empty storage bins include:

Tempo SC Ultra (a.i. is cyfluthrin) used as a liquid spray

Diacon-D IGR (a.i. is s-methoprene) used as a dust application

Insecto (a.i. is diatomaceous earth) used as a dust application

Before using any product to treat grain bins, always read the most current label for the product to assure that the product is used correctly.  This is for the protection of the grain to be stored in the bin as well as for the protection of the applicator of the product.  Labels for products are subject to change from one year to the next, product registrations can be changed and/or canceled and rates may be changed.  Errors made because of not reading the most current label could result in injury to the applicator or contamination of the grain with a non-labeled product making it unsalable.