August 23, 2021

Late spring, summer and early fall are the times of the year when insects are most active. They fly and walk 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. With only a few exceptions, most of the stored-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, 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 people 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 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. 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, but they also are very difficult to control.
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 the can be 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.
Beyond the bin
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 identify the last grain crop, 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 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, remember the dosage is based on the total volume of the area the fumigant is being released.
Fumigant precautions
There are several precautions to be addressed when using aluminum phosphide as a fumigant.
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. Don’t use the product is it is not properly sealed.
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.
Phosphine gas is a highly toxic compound and is both colorless and odorless. It must be handled with care following all safety requirements listed on the label and in the applicator's manual.
For safety purposes, the manufacturer of aluminum phosphide includes an indicator compound to warn people 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 accustomed to the odor very quickly and be undetectable. Thus, absence of the odor does not mean safety.
The aluminum phosphide label and applicator's manual have gone through major revisions recently — read both very closely to use this product correctly.
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 reinfestation.
Products for treating bins
There are very few products left registered for use around and on stored grain bins. 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 label to ensure that the product is used correctly. Labels for products are subject to change from one year to the next. Product registrations can be changed 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 nonlabeled product making it unsalable.
Young is an Ohio certified crop adviser.
Source: Ohio State University Extension Agronomy Team, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.
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