Monitoring stored grain for insect pest infestations

Jan 21, 2025

One of the best ways to prevent insect infestations is to monitor bin-stored grain every 2 weeks to detect early signs of deterioration or infestation. This section explains several devices you can use to sample grain and check for insects.

Trapping insects

Trapping to determine the presence of insect pests in stored grains is a simple and cost-effective way to monitor for infestations and identify insect pests so that you can make decisions about insect control.

How to use pit-fall traps

Probe pit-fall traps are one of a variety of traps that have been developed for use in stored food. The photo shows two kinds of pit-fall traps:

A pheromone-baited pit-fall trap (top left corner)
Open trap (left) and closed trap (right). The trap is closed when in use.
A pheromone-baited probe pit-fall trap (bottom right corner)
Intact trap with a string attached to it and the internal components of the trap

Push probe pit-fall traps in the grain at the top of the pile, near the centre. When the grain becomes cooler than ambient conditions, insects tend to migrate to this area of the bulk.

Grain that is in storage should be level, and probe pit-fall traps should be placed in the grain as early as possible. Insert them so that the upper portion of the trap is no more than a few centimetres below the surface. Attach brightly colored twine or rope to the trap so that it can be readily retrieved.

Remove the trap every 10 to 14 days to inspect it for insects. Continue doing this until the grain temperature is below 18°C. After this, monthly monitoring is sufficient. If insects are discovered, use treatments such as aeration; moving and turning the grain; or fumigation or contact insecticide application.

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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.”