The Maine Pest Calendar

Maine’s pest pressure is seasonal in a way that southern states’ is not, and the timing is not guesswork: UMaine Cooperative Extension, its Tick Lab and the Maine Center for Disease Control and Prevention all publish when the main household pests appear. This calendar is built from those sources. It deliberately does not use the business’s own job history for timing, because those jobs are not dated precisely enough to support a month-by-month claim.

The two dates that matter most

Late summer, for sealing. UMaine Extension’s cluster fly fact sheet has the adults hunting for attics and wall voids in late summer, and Extension’s pages on the western conifer seed bug and the multicolored Asian lady beetle put their move indoors at the end of summer, early fall and October. The cracks, vent screens and utility gaps that admit all three also admit mice, so one round of sealing in August does several jobs at once. The overwintering insects guide covers that work in detail.

June, for ticks. The UMaine Tick Lab describes deer tick nymphs as about the size of a poppy seed and puts their numbers at a peak in June and early July. A tick that small is easy to miss, so habitat work in spring and careful daily checks through early summer cover the stretch that matters. Tick control explains what yard treatment involves.

Month by month

January. The quiet month outdoors. Cluster flies in the walls are dormant; UMaine Extension’s fact sheet says they become active on warm days or when indoor heat is turned on, and only after a period of cold. If you hear activity in the ceiling, note where and when rather than guessing.

February. Sunny spells bring the first insects to south- and west-facing windows. A vacuum is the right tool. Write down which rooms — that list is next August’s sealing plan.

March. The Maine Forest Service says browntail moth webs within safe reach can be clipped between October and March, and that caterpillars leave the webs to feed in mid-April, after which clipping no longer helps. (Blouin Pest Services does not treat browntail moth; this is homeowner work or a job for a licensed arborist.)

April. The UMaine Tick Lab puts the first adult deer tick peak in April or May. Rake leaf litter away from the lawn edge and the play area. Maine CDC’s tick-safe-zone advice includes keeping the lawn mowed, moving wood piles and bird feeders away from the house, and laying a 3-foot strip of wood chips or crushed stone between lawn and woods.

May. Overwintered yellowjacket queens are out choosing nest sites, according to the Maine State Apiarist. UMaine Extension adds that nuisance nests are most easily removed in early spring, before the colony grows, so a weekly look under eaves, deck rails and the shed door pays off now. Boxelder bugs that wintered indoors are heading out; Got Pests? describes them gathering on the south and west sides of buildings on sunny days, trying to get in each autumn and out each spring.

June. Nymph ticks at their peak (UMaine Tick Lab). Carpenter ant workers indoors this time of year have often come in from an outdoor nest looking for food and water, by UMaine Extension’s account — worth tracing back rather than spraying where they are seen.

July. Wasp colonies are growing quickly. Maine CDC tests mosquito pools, birds and animals for EEE, Jamestown Canyon and West Nile viruses during the season, and posts its surveillance reports publicly; empty anything holding water around the house.

August. UMaine Extension describes wasps as most troublesome in mid to late summer, when colonies peak. Cover food and drinks outdoors and keep bin lids tight. This is also when cluster flies start looking for winter quarters, and when Extension says their outdoor resting areas can be treated.

September. Western conifer seed bugs start moving in (UMaine Extension). Finish screening soffit and gable vents and sealing gaps on the sunny side of the house.

October. Asian lady beetles arrive, which is why UMaine Extension lists “Halloween lady beetle” among their nicknames. The second adult deer tick peak comes in late October (UMaine Tick Lab), so hunting and leaf-raking season is still tick season.

November. The Maine State Apiarist notes that yellowjacket colonies die after the first hard frost, so a nest found now rarely needs treating. Maine CDC says two hard frosts across most of the state dramatically reduce the risk of mosquito-borne disease.

December. Interior season. Firewood brought in now deserves a look first — UMaine Extension advises always checking it for carpenter ants before it comes indoors. Whatever got in during the autumn is now in the walls until spring; the useful work is noting where, so the gaps can be closed before next August.

What the calendar does not cover

Bed bugs and cockroaches do not follow the seasons — they follow travel, furniture and shared walls, and they arrive whenever they arrive. Mice and rats are a structural problem more than a seasonal one; this page does not put a month on their arrival because we have not found a Maine source that does, but the late-summer sealing above closes the same gaps they use. See rodent exclusion for that work.

Two rules that cover most of it

Fix water, and most insect problems get smaller. UMaine Extension’s carpenter ant fact sheet traces infestations to leaks around chimneys, roof valleys, gutters, windows and door frames, and to plumbing leaks under kitchens and bathrooms. A gutter that overflows onto a sill is both a carpenter ant risk and a pool of standing water; mosquito control covers the water side.

Seal before the cold, not during it. Every overwintering insect in Extension’s fact sheets is looking for a way in from late summer onward. Sealing in August is prevention; the same work in January is a repair with the insects already inside.

Updated 2026-10-04.