How to Control Soybean Pests During Storage

Capturing the full value of your soybean crop takes more than just harvesting them at the right time in the fall. Proper soybean storage is critical for protecting your hard-earned yield from devastating pests like mice, soybean beetle, soybean weevil, soybean moth, fungi and bacteria. Here’s how to keep your soybeans and bins clean and mitigate the risk of pests.

How soybean pests affect soybean storage

In 2023, invertebrate pests including insects, mites and mollusks reduced U.S. bushels across 19 states by 1.6%. And throughout that growing season, farmers shelled out $669.3 million to manage soybean pests.¹

It’s natural to focus on pests during the growing season, but pest management must persist post-harvest to safely maintain your crop in bagged or binned storage facilities. Problems caused by pests during the post-harvest season include:

• Grain losses from pests that eat your soybeans
• Spoilage of grain from bacteria, fungi or mold
• Financial penalties or outright crop rejection at the elevator due to poor grain quality

You can address these and other challenges with an integrated pest management (IPM) strategy that includes sanitation of your storage facilities, identification of specific pests, regular monitoring for potential problems and preventive practices.

Soybean pests to watch out for during storage

Several soybean pests make the post-harvest season a chore. Here’s the shortlist of common soybean pests to look for.

Soybean beetles: identification

Soybean beetles do the most damage to your stored crop in their larval and adult stages.
Many are called external feeders or “bran bugs,” who enjoy a buffet of grain dust, cracked kernels and other crop debris without crawling inside your soybeans to fill their bellies. Common external feeders include:

• Sawtoothed grain beetle
• Red and confused flour beetles
• Flat grain beetle

Meanwhile, foreign grain beetle and hairy fungus beetle chow down on molds and fungi present in overly moist grain bins, making it important to monitor humidity.

Soybean weevils: identification

Weevils are a type of beetle. From the farmer’s perspective, the biggest difference between a weevil and other beetles is that many weevils prefer to eat the insides of soybeans, whereas beetles often feed on the exterior of the kernel.
Weevils that find their way into bins include:

• Granary weevil
• Rice weevil

Inspectors with the U.S. Department of Agriculture’s Federal Grain Inspection Service (FGIS) can deem your grain infested if they observe one of these scenarios in a sample of your stored soybeans:

• Two or more live weevils
• One live weevil and five other insects that damage grain
• 10 other live insects that damage grain²

These guidelines apply to all injurious insects described in this article. Such pests can be costly because you will need to fumigate the contaminated bin to reduce insect populations (if you are certified to do so). Alternatively, you can feed infested grain to livestock or sell the grain at a discount.

Indianmeal moths and other lepidopteran pests in soybean storage

The larval stage of the Indianmeal moth can be a real problem during soybean storage. This caterpillar grows up to 2/3" long and feeds on fine particles located in the top 3” to 6” of your grain,³ creating a webbing where they’ll eventually undergo metamorphosis into the flying moth. Female moths can lay more than 200 eggs in or close to food sources.⁴

Rodents and their byproducts in soybean storage

Mice and rats are among the most common rodents that threaten stored soybeans. They gain access to bins via gaps. Not only do they eat your crop, they also leave droppings and urine, which can contaminate soybeans.

Soybean storage practices to reduce pest damage

Here are several steps you can take to limit the risk of soybean pests taking up residence in your grain bins.

Storage facility preparation to prevent soybean pests

Clear old crop residue out of bins, any related equipment and the area surrounding your storage facilities. Look for and seal cracks and entry points that could invite pests.

Moisture management to limit soybean pests

Ensure your bins are set up to keep soybeans at the right moisture level. Aim for under 11% moisture. This will limit insect reproduction and discourage the development of pests such as mold.
If needed, consider an aeration system to keep soybeans within 10-15 degrees (F) of outdoor temperatures during the fall and winter seasons, and within 40-60 degrees of outdoor temps during spring and summer.⁵

Continual monitoring of soybean storage conditions

Keeping pests out of your soybeans post-harvest isn’t a “set it and forget it” type of activity. You’ll need to monitor your storage facilities regularly.

Double-check details such as grain moisture and temperature. Make a point of checking bins every two weeks, and if you see beans are starting to crust, consider aeration to keep air moving and maintain good crop quality.⁶

Soybean pest control methods during storage

During storage, chemical, non-chemical and biological tactics should all be considered to keep soybean pests in check.

Chemical treatments

If you experience a severe pest infestation once your bin is full of soybeans, a fumigant such as carbon dioxide (assuming you’re certified in its use) can be an effective treatment. Keep in mind, though, that this process must happen in a completely sealed environment, that it takes days to work effectively and that no residual protection remains once fumigation ends.⁷ Continued vigilance is needed to prevent the return of pests.

Talk to a certified professional or a trusted adviser for recommendations about specific bin- and storage-related pest-control solutions.

Non-chemical strategies to control soybean pests

There are several non-chemical paths to explore for pest control in your bins, as well.

1. Keep the temperature low. Grain should be cooled to between 50 F and 55 F to halt insect activity. It can also be heated to 130 F for half an hour to kill insects.
2. Consider using diatomaceous earth. When applied as a protective barrier, diatomaceous earth saps insects of the moisture they need to live.
3. Explore insect growth regulators such as methoprene. Such a regulator won’t harm grain (and, full disclosure, it doesn’t harm adult insects, either) but can prevent larvae from turning into adult insects, curbing the reproductive cycle of common soybean pests such as soybean beetle and soybean weevil.

Keep tabs on pests using pheromone traps and other traps placed inside the bin’s side access panel.⁸

Biological agents

Nature-based solutions can be another option for keeping soybean pests out of your bins after harvest.
One popular option among farmers growing soybeans is Bacillus thuringiensis (Bt). This product, a bacterium, can either be applied in an empty grain bin pre-harvest or as a top-dressing in a bin full of soybeans to target moths, including the grain moth and the Indianmeal moth.⁹

Be sure to select an allowable formulation of Bt, which can kill the moth’s caterpillars that hatch in stored grain. The bacterium is only effective at the moth’s larval stage, and it only works once caterpillars have eaten it.
Bt won’t work on moth eggs, pupae or adults.

Keep your guard up and soybean pests out

As with other seasons of soybean production, the post-harvest period demands your vigilance and attention.

Experts are available to help you make good management decisions that can reduce the risk of pests in your soybean bins with an integrated approach. Reach out to your seed retailer, a nearby extension office agent, or a seed company professional like your regional BASF representative.

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Endnotes

1. “Soybean Invertebrate Loss Estimates from the United States – 2023.” Crop Protection Network, 15 Jan. 2024, https://cropprotectionnetwork.org/publications/soybean-invertebrate-loss-estimates-from-the-united-states-2023. Accessed 5 May 2025.
2. "§ 810.107 Lot as a Basis for Sample.” Legal Information Institute, Cornell Law School, https://www.law.cornell.edu/cfr/text/7/810.107. Accessed 7 May 2025.
3. Krupke, Christian H., et al. Field Crops: Corn Insect Control Recommendations. Purdue Extension, Purdue University, Jan. 2023, https://extension.entm.purdue.edu/publications/E-66.pdf. Accessed 5 May 2025.
4. “Indian Meal Moth.” Colorado State University, Department of Agricultural Biology, https://agsci.colostate.edu/agbio/ipm-pests/indian-meal-moth-2/. Accessed 5 May 2025.
5. “Enhancing Soybean Storage Starts with Harvest Moisture.” North Dakota State University Agriculture, https://www.ndsu.edu/agriculture/ag-hub/enhancing-soybean-storage-starts-harvest-moisture. Accessed 5 May 2025.
6. “Storing Soybean.” Iowa State University Extension and Outreach, https://crops.extension.iastate.edu/encyclopedia/storing-soybean. Accessed 5 May 2025.
7. “Preparing Grain Storages for Harvest.” Penn State Extension, 3 Aug. 2022, https://extension.psu.edu/preparing-grain-storages-for-harvest. Accessed 5 May 2025.
8. Kandel, Hrvoje. Soybean Growth and Development. South Dakota State University Extension, Mar. 2020, https://extension.sdstate.edu/sites/default/files/2020-03/S-0004-42-Soybean.pdf. Accessed 5 May 2025.
9. “Management of Stored Grain Pests in Organic Systems.” Penn State Extension, 14 July 2021, https://extension.psu.edu/management-of-stored-grain-pests-in-organic-systems. Accessed 5 May 2025.