Iowa Seasonal Pest Calendar for Insects, Rodents & Bats

Indoor pressure at its highest — cold pushes rodents into walls and basements.

Boxelder bugs and lady beetles sit dormant indoors; a warm day wakes a few up.

Scratching or chirping in the attic on mild nights signals a roost overhead.

Peak indoor nesting and feeding activity before spring.

Quiet month — mostly basement and garage sightings.

Still tucked in wall voids and attics.

Note entry points now; humane exclusion is planned for later in the year.

First trails appear along foundations and kitchen edges.

Warming garages and crawl spaces bring webs back.

Watch for mud tubes and damp sill plates before swarm season.

Transition month — some move back outdoors, others stay and breed.

Bats begin leaving winter roosts; inspect, do not seal blindly.

Carpenter ant swarmers show up indoors near windows and light.

Swarming season — winged termites near foundations need a same-week look.

Egg sacs hatch along eaves and window frames.

Queens start small nests under soffits, decks, and grills.

Late-month hatch after the first warm rains.

Outdoor breeding ramps up around sheds and outbuildings.

Heaviest foraging of the year — kitchens, patios, and slabs.

Colonies actively feeding on wood in contact with soil.

Exterior web buildup on porches and siding.

Nests still small — the cheapest time to knock them down.

Standing water from spring storms fuels the first big wave.

Tall grass, timber edges, and pets bring ticks to the door.

Maternity season begins — exclusion is put on hold to stay humane.

Satellite colonies expand into wall voids.

Yard treatments matter most now through August.

Nests visibly larger and more defensive.

Feeding on the insect boom around exterior lights.

Peak bite risk for people, dogs, and livestock.

Active feeding continues out of sight.

Flightless pups present — sealing now would trap them inside.

Evening cookouts get unusable without yard protection.

Large colonies near doors, playsets, and barns.

Still heavy indoor foraging in hot, dry stretches.

Web counts climbing toward the fall peak.

Flea populations explode in pet bedding and carpet.

Still maternity season — inspection only, no sealing.

Most aggressive stretch of the year around food and trash.

Late-summer humidity keeps pressure high.

Colonies at maximum size before fall slowdown.

Big webs on porches and under eaves.

Late month they start gathering on sunny south and west walls.

Exclusion planning window opens once young bats can fly.

Boxelder bugs, Asian lady beetles, and stink bugs mass on siding looking for a way in.

Highest indoor sightings of the year.

First cool nights push rodents toward foundations and garages.

Colonies at full size and scavenging hard.

Tapering off but still biting until a hard frost.

Prime humane exclusion window — bats are flying and free to leave.

Peak push indoors through gaps in siding, soffits, and window frames.

Heaviest entry pressure of the year — exclusion beats trapping.

Basements, garages, and storage rooms fill up.

Colonies dying off; old nests are not reused.

Best sealing window before bats settle into winter roosts.

Indoor pressure peaks as temperatures drop.

Now dormant inside wall voids and attics.

Fewer new webs; existing ones persist in basements.

Exclusion window closing — inspect and plan for late summer.

Full indoor season — droppings, gnawing, and pantry damage.

Hidden indoors; warm spells bring a few to windows.

Roosting bats stay put — document activity for a summer fix.