There are several tactics to control pests in grain bins, many of which begin before the grain goes into the bin. The goal is to begin storing your grain with the lowest possible numbers of insects. Strategies include cleaning empty bins inside and out, managing weed or rodent problems, and sealing any cracks or gaps. However, as we approach spring with increasing temperatures, small insect populations can quickly increase and turn into large populations.
Storage periods of one year or longer are common. During this time, grain is undisturbed and remains at risk for insect damage. Risk is especially high as Alabama experiences warm, moist weather from spring through fall. Warm grain is ideal for stored product pests. Higher temperatures mean insects feed, grow, and reproduce faster. During this time, if your bin contains high numbers of insects, an additional treatment may be warranted. Treatments for infested grain that is already in the bin are discussed below.
Top Dress Treatments
If the grain is going to be stored for more than a few months, and a protectant was not added when the grain was loaded into the bin, a top dress treatment may be helpful. Top dress treatments are applied to the surface of the grain. These treatments prevent pest infestations from the top of the structure. Most top dress treatments are incorporated into the top four inches of the grain. Some require a greater mixing depth and some are applied with no mixing. Read label for specific instructions. A list of insecticides approved as top dress treatments can be found in our Stored Grain IPM Guide.
One particular pest that is problematic is the Indianmeal moth (see figure above). Indianmeal moths feed on damaged kernels. They are typically found in the top four inches of grain. Activity will pick up in the spring as temperatures warm. The top of the grain is the first to warm up and this is where you may see Indianmeal moths. An infestation of these moths can contaminate the grain with their frass and silk webbing. Live insects and insect parts in grain can lead to dockage.
Indianmeal moth infestations are typically limited to the top few inches, so for this particular pest, fumigation is not required for control. If you’ve had problems with Indianmeal moths previously, or find populations when sampling, a headspace treatment may be warranted. Polyvinyl strips that contain the insecticide dichlorvos can be hung in the headspace.
Fumigation may be required when insect populations become too high and cannot be controlled with other treatments. Aluminum phosphide is the chemical used for fumigation. It is sold typically in pellet or tablet forms, or as paper sachets, plates, or strips. When these are exposed to moisture and heat, they give off phosphine gas. Inhalation of fumigants is the most common and dangerous method of exposure.
Mild exposure can lead to an overall feeling of sickness, ringing in ears, fatigue, nausea, and pressure in the chest. Moderate poisoning can lead to weakness, vomiting, stomach and chest pain, diarrhea, and difficulty breathing. Severe poisoning can occur within a few hours to a few days following exposure. This includes fluid forming in the lungs, dizziness, blue or purple skin, unconsciousness, or death.
A fumigation management plan is necessary before any fumigant is applied. The fumigant must be left inside the bin long enough to be effective. Check the label for specific requirements. Approved fumigants can be found here.
If you are unfamiliar with grain bin fumigation, hire an outside company with trained professionals.