Use Grain Temperature to Schedule Winter Insect Checks

Keep the benefit of cooling

Cooling helps slow insect activity in stored grain. Keep that benefit working with regular checks based on the grain’s temperature—not the outdoor forecast. During winter, include the bin center and look for feeding damage as well as live insects. Cold weather alone does not establish that insects have died.

Set the next check from grain temperature

South Dakota State University Extension’s guidance, updated August 28, 2026, gives this inspection schedule:

– Grain above 55–60°F: inspect every week.
– Grain below 55°F: inspect every two weeks.

Use measured grain temperature to choose the interval. For example, grain below 55°F still belongs on a two-week checking schedule even when outdoor temperatures stay below freezing. Put the next inspection on the calendar after each check.

Some lots need closer attention. Iowa State University Extension’s January 4, 2023 winter-storage guidance recommends more frequent checks for low-test-weight grain, damaged grain with broken kernels, or grain containing a high percentage of fines—small grain particles and debris. Localized warmth or unusual odors also warrant examination rather than waiting for the next scheduled check.

Include the center, not just the walls

SDSU Extension notes that insects move toward the bin center during winter. Checking only grain near the walls can miss that location.

Its grain-probe sampling guidance calls for samples from the surface and base of the grain mass, working from the center toward the walls with sampling locations no more than 20 feet apart.

These are sampling locations, not directions to walk onto stored grain. Bridged or crusted grain can collapse. If entry is necessary, use established bin-entry safety procedures, including locking out unloading equipment and having another person present; do not treat sampling as a reason to enter alone.

Separate insect clues from other storage warnings

Look through samples for live insects and these feeding signs identified by University of Minnesota Extension in its September 23, 2021 guidance:

– Hollowed kernels or seeds.
– Beetle exit holes.
– Webbing from moth larvae that binds grain into clumps.

Immature insects can remain hidden inside kernels, so visible feeding damage matters even when you do not see moving insects.

Also investigate localized warmth, unusual odors and surface crusting, but do not assume those signs confirm insects. Iowa State Extension identifies musty or sour smells as signs of mold growth. Uneven grain temperatures can move moisture toward the surface, causing spoilage and crusting.

At your next check, record the grain temperature, where you sampled and what you found. That gives you a clear next inspection date and specific locations or warning signs to follow up.