Prevent Stored Grain Pest Issues Before Winter

Sep 29, 2021

Late summer and early fall is time ensure infested and spoiled grain in bins from previous harvests won’t cause more problems for this year’s harvest. Over the summer, insect infestations may have grown in grain bins, especially in areas where spoiled grain accumulated even after being mostly emptied (Fig. 1). Keeping good sanitation practices prior to putting the next harvest into storage will help break pest cycles and reduce the likelihood of issues with spoilage or price docking at the elevator. Once grain is in the bin, options to manage existing insects are very limited, especially grain that is going to be stored through the following spring or summer.

Figure 1. Insect feeding damage in spoiled corn

Figure 1. Insect feeding damage in spoiled corn. Photo: A. Hanson

Integrated pest management for insects in stored grains is closely tied to sanitation to also prevent grain from spoiling and overheating. Clean bins and equipment, maintain temperatures that are not ideal for insect development as long as possible, and consider residual insecticides when insects have continued to be an issue in previous years.

Common insect species can include: saw-toothed grain beetle, grain weevils, and India meal moth. Many of these species are generalists, so they can infest corn, soybeans, wheat, and other grains. Direct feeding damage can be a more obvious symptom of insect issues with hollowed out seed and exit holes from beetles or webbing from moth larvae that causes grain to clump (Fig. 2). Immature stages of many of these species live within the seed and will not always be readily visible. This also offers them some protection from transport, augering, or bin stirators.

Figure 2. Moth feeding damage and webbing on stored soybeans. Cast skins from pupae before emerging as adults are also visible. Photo: A. Hanson

Clean bins and other equipment
Reducing the amount of material insects can use as shelter or to reproduce is key for stored grain pest management as small amounts of infested or moldy material can infest clean incoming grain.

At least a few weeks before filling a bin, vacuum or sweep out old material. Accumulations of chaff, fines, and broken kernels are preferred habitat for stored grain insects. While a bin may appear clean, don’t forget about areas where these materials may accumulate out of sight, such as underneath slotted flooring.

Once a bin is cleaned out and checked for cracks or openings where insects might gain entrance, check any harvest or transport equipment where old grain may not have been cleaned out last year. An unused auger or corners of a grain truck that were not entirely cleaned out can harbor insects over the summer that will reinfest your harvest and rebuild pest populations.

Maintain cool temperatures
During summer and fall insects will be near the surface of the grain mass, while in winter they will move to the center of the pile where infestation may not be noticeable until temperatures rise. Insect feeding can cause temperatures in a bin to rise to 110°F, which can cause issues both for spoilage and make the grain mass even more ideal for insect development.

When grain temperatures are below 50°F, insect development slows, and at 25°F, insect activity mostly stops. Some mortality can also occur at colder temperatures, though this is highly dependent on species, the actual temperature experienced in the grain, and the length of cold exposure. From both a grain quality and insect management approach, it is important to take advantage of cold Minnesota nights to run fans and move cold air across the entirety of the grain mass.

Insecticides

Insecticides will not be effective if grain still has to be dried. Running grain through augers and especially heat will degrade insecticides, so this option should be reserved for final storage rather than a drying bin. While fumigants are available for already filled and infested bins, these can be difficult to use to ensure coverage across the entire grain mass. Instead, prevention through sanitation and residual insecticides two to three weeks before putting new grain in a bin will typically be the easier and less expensive option.

Residual insecticides can be applied in a few different manners as a protective strategy. Surfaces of bins can be treated to target adult insects that do manage to enter through openings in the bin or remain wandering the bin after food sources have been removed. These treatments need to dry over at least 24 hours to be effective, and there should be at least a two week period after application until the bin is filled. Other strategies include treating the entire grain mass as it passes from the auger into the bin, or a top dressing treatment to protect against insects entering from the roof as long as the top layer is not disturbed. Always follow pesticide label requirements and guidance for specific uses and insect species.

Source : umn.edu

Video: Why Your Food Future Could be Trapped in a Seed Morgue

In a world of PowerPoint overload, Rex Bernardo stands out. No bullet points. No charts. No jargon. Just stories and photographs. At this year’s National Association for Plant Breeding conference on the Big Island of Hawaii, he stood before a room of peers — all experts in the science of seeds — and did something radical: he showed them images. He told them stories. And he asked them to remember not what they saw, but how they felt.

Bernardo, recipient of the 2025 Lifetime Achievement Award, has spent his career searching for the genetic treasures tucked inside what plant breeders call exotic germplasm — ancient, often wild genetic lines that hold secrets to resilience, taste, and traits we've forgotten to value.

But Bernardo didn’t always think this way.

“I worked in private industry for nearly a decade,” he recalls. “I remember one breeder saying, ‘We’re making new hybrids, but they’re basically the same genetics.’ That stuck with me. Where is the new diversity going to come from?”

For Bernardo, part of the answer lies in the world’s gene banks — vast vaults of seed samples collected from every corner of the globe. Yet, he says, many of these vaults have quietly become “seed morgues.” “Something goes in, but it never comes out,” he explains. “We need to start treating these collections like living investments, not museums of dead potential.”

That potential — and the barriers to unlocking it — are deeply personal for Bernardo. He’s wrestled with international policies that prevent access to valuable lines (like North Korean corn) and with the slow, painstaking science of transferring useful traits from wild relatives into elite lines that farmers can actually grow. Sometimes it works. Sometimes it doesn’t. But he’s convinced that success starts not in the lab, but in the way we communicate.

“The fact sheet model isn’t cutting it anymore,” he says. “We hand out a paper about a new variety and think that’s enough. But stories? Plants you can see and touch? That’s what stays with people.”

Bernardo practices what he preaches. At the University of Minnesota, he helped launch a student-led breeding program that’s working to adapt leafy African vegetables for the Twin Cities’ African diaspora. The goal? Culturally relevant crops that mature in Minnesota’s shorter growing season — and can be regrown year after year.

“That’s real impact,” he says. “Helping people grow food that’s meaningful to them, not just what's commercially viable.”

He’s also brewed plant breeding into something more relatable — literally. Coffee and beer have become unexpected tools in his mission to make science accessible. His undergraduate course on coffee, for instance, connects the dots between genetics, geography, and culture. “Everyone drinks coffee,” he says. “It’s a conversation starter. It’s a gateway into plant science.”