The pest calendar
Pest pressure runs on the seasons, and the cheapest work is always the work done one season early. The rhythm below is the broad North American pattern — a Florida spring and a Manitoba spring are weeks apart, so read it by climate, not by the letter of the month.
March – May
Spring
- Termitesswarm season — winged reproductives emerge, often the year's only visible evidence
- Antscolonies wake hungry and send scouts indoors
- Wasps and hornetsqueens start new nests, small enough to deal with easily
- Birdsnesting begins, and with it the legal protections around active nests
Spring is inspection season. Walk the foundation looking for mud tubes and winged swarmers, knock down last year's wasp nests before new queens reuse the eaves, and deal with a golf-ball-sized nest now rather than a football-sized one in August.
June – August
Summer
- Mosquitoespeak breeding in any standing water
- Wasps and hornetscolonies reach full size and full defensiveness
- Fleas and tickspeak activity for pets and yards alike
- Flies and gnatsfruit and drain flies thrive on heat and fermentation
- Beesswarms house-hunt; established colonies fill wall voids with comb
Summer is source control: tip standing water weekly, keep bins closed and drains clean, and treat pets on schedule. Wasp and bee problems at height or in structure are professional calls — this is the season the 24-hour listings on this site exist for.
September – November
Autumn
- Rodentsthe ingress season — mice and rats move indoors as nights cool
- Spidersthe visible season, as males wander and webs go up at lights
- Flies and gnatscluster flies gather on warm walls and slip into voids to overwinter
- Beetles, moths and mitespantry pests surface as dry goods stocked up for winter sit longer
Autumn is exclusion season and the best value work of the year: seal the gaps, screens and door sweeps before the first cold night, because every rodent kept out now is a wall you do not open in January. Check the pantry's oldest packets while you are at it.
December – February
Winter
- Rodentsestablished indoor populations are now at their most audible
- Cockroachesheated buildings are their year-round climate — winter changes nothing indoors
- Bed bugstravel season moves them; they do not care about the weather
- Wildliferaccoons and squirrels den in attics and chimneys
Winter problems are indoor problems, which makes them diagnosis problems: noises in walls, droppings, sightings in heated rooms. This is the season to book the unhurried inspection — and in warm-climate states, note that termites and mosquitoes never really left.
General North American seasonality, written by this site · regional timing varies with climate · each pest links to its full guide