This calendar follows the seasons the Colorado sources describe: boxelder bugs gathering on warm fall and winter days, and subterranean termites present in the state. It is limited to those sourced timings, so months with no sourced pest pattern say so rather than guessing.
Key takeaways
- Late summer is the time to walk the house and list the gaps before the autumn.
- Early to mid autumn is when boxelder bugs gather on warm sunny walls, per CSU.
- Winter warm spells can still bring insects out of wall voids.
- Spring is the right time for a termite inspection and for a screen and vent check.
- Months with no sourced pattern are left open rather than filled with guesses.
- Use the calendar to book visits early, not after the first sighting.
Why a calendar, and why only these seasons?
A calendar helps a homeowner book the right visit at the right time. This one uses only the seasons the sources support, so it does not present a pattern the research did not find.
A pest calendar can look authoritative while being mostly guesswork. The sources this site uses describe two patterns clearly for Colorado: boxelder bugs that gather on building exteriors on warm fall and winter days, and subterranean termites that are present in the state. The calendar builds around those and leaves the rest open.
A month with no sourced pattern is not a month without pests. It is a month where this site has no source to name a pattern, and a homeowner who sees activity should call for a visit at any time. The calendar is a planning tool, not a promise that nothing will happen in the months it leaves blank.
Late summer: walk the house and list the gaps
In late summer, walk the outside of the house, mark the window and door frames, the siding joints, the soffit and the penetrations, and note any gap or torn screen. This list becomes the sealing job for early autumn.
The late summer walk is the most valuable visit of the year for a homeowner who does it themselves. A flashlight on a cloudy day shows where light passes through a frame, and a piece of tape marks each spot. The list is written with the location of each gap, and it is kept with the house records.
The walk also checks the wood and the soil. Note any step, post, fence attachment or deck board that touches the ground, and any firewood against the foundation. Those are the prevention items CSU names for termites, and they are easier to fix before the autumn than during it.
Early autumn: seal before the warm spells
Early autumn is the best time to seal the gaps, before the first warm afternoon brings boxelder bugs to the sunny walls. Sealing done in this window has time to be tested before the cold months.
CSU Extension describes boxelder bugs gathering on building exteriors on warm fall days and entering through cracks. The sealing list from late summer is applied in mild weather, when the caulk and the foam set well, and the south and west faces are done first.
A vacuum is kept ready for the bugs that have already got inside. CSU advises vacuuming rather than crushing, and the bag should be sealed and removed from the house once the room is clear.
Mid to late autumn: check the sealing
In mid to late autumn, walk the house again on a warm afternoon and look for bugs on the walls and in the window tracks. A bug on a sealed wall points to a gap that was missed.
The autumn check is a short walk on a warm day, because the gathering is most visible when the sun is on the walls. Note each bug, its wall and its position relative to the windows. A cluster at one corner shows where the next gap is, and it is added to the list.
If a residual has been placed on the foundation, check that it is still in place and has not been washed away by autumn rain. CSU presents a residual as a longer-term option, so the check is about whether it is still doing its job.
Winter: watch for warm-day indoor activity
Winter brings warm spells, and a warm day can bring insects out of wall voids and into a room. Note any activity on a warm winter day and keep the sealing list up to date for the spring.
CSU says the boxelder bugs gather on warm fall and winter days, so a warm spell in January can bring a few insects into a room that looked clear in November. A few insects after a warm day is a pattern to note, not an emergency. Dated notes help the spring visit.
Winter is also the time to keep crawl space vents clear of snow and to check the space for damp after a heavy storm. Standing water in a crawl space is a condition to note and to fix before the spring thaw.
Spring: termite inspection and screens
Spring is the best time for a termite inspection, when the soil is clear and the crawl space can be reached. It is also the right time to replace torn screens and check the vents that winter may have damaged.
A termite inspection in spring gives the inspector clear access to the soil line and the sill, and the report is ready before the warm months. CSU’s prevention advice applies at any time of the year, and a spring walk checks the wood on soil and the cracks in the foundation.
Screens and vents are often damaged by ice and wind over the winter. A torn screen is an open route for the next autumn, so replacing it in spring prepares the house for the boxelder bug season.
Summer: keep the water and wood in order
In summer, keep the mulch below the siding, the downspouts extended and the firewood away from the house. Summer is also when a homeowner can plan the next autumn’s sealing from the late summer walk.
A dry summer can make a homeowner less aware of moisture, but a heavy summer storm can move soil and open water paths. Check the grade after the storm, and keep the downspouts clear of debris so the water runs away from the wall.
Summer is the right time to plan a visit for the autumn, to book the technician early and to order any sealing material needed. A visit booked in August is easier to fit than one booked after the first warm day in October.
Reading the calendar against a real house
The calendar is a set of dates, but a house is a set of conditions. Lay the calendar over the house’s own record, and the timing for each visit becomes clear.
Take the list from the late summer walk and mark each item with the month it should be sealed by. The gaps on the south and west faces go first, because the sun drives the gathering there. The gaps on the north and east faces follow, since they are visited less often by the sun but are still entry points.
Note also the items that depend on the ground, such as the grade, the mulch and the woodpile. Those are checked in spring and again after heavy rain, because soil moves with the weather and the calendar cannot predict that movement. A homeowner who keeps the record in one place will see at a glance what is due and what is done.
When to call a professional during the year
Call a professional when a sign appears that the homeowner cannot explain, when a repair involves structural wood, and in any month when an inspection is needed to settle a question about termites.
A mud tube, hollow wood, swarmers or damage at the sill are reasons to call at any time of year, not only in spring. The inspection is the way to confirm what is present, and the calendar should never delay a call when a sign is seen.
A professional is also useful for a whole-house sealing check in late summer, because the technician can see gaps a homeowner may miss. That visit fits the calendar well, because it sets the list for the autumn in one go.
What a homeowner can do in a single month
Each month has one job that matters most, and a homeowner can do that job in an afternoon. The list below is the work for a single month in each season, and it stays inside the sourced patterns.
In late summer, the job is the walk and the list. In early autumn, the job is the sealing and the vacuum kept ready. In mid autumn, the job is a warm-day walk to find the bugs on the walls. In winter, the job is to note a warm-day indoor sighting and to keep the crawl space vents clear.
In spring, the job is the termite check on the soil line and the screen replacement. In summer, the job is the water and the wood, with a booking for the autumn visit made early. Each single job is small, and together they keep the house on the calendar.
Frequently asked questions
Why does the calendar not give a month for termites?
The sources describe termites as present in Colorado and say damage is less common than in wetter states, but they do not give a swarm month for the Boulder area. The calendar does not guess one.
What if I see insects in a month that is not on the calendar?
Call for a visit. The calendar is a planning guide, and an insect seen in any month is worth a note and a look by a technician.
Can I book the visit in the same month I see the bugs?
Yes, but booking early in the season is easier. The best visits are scheduled before the gathering starts, and a late booking may fall after the sealing is needed.
Does the calendar apply to every house in Boulder County?
It describes the sourced Colorado patterns and applies broadly to the county. The building, its gaps and its lot decide what is found on any particular address.
Should I use a calendar reminder for each job?
Yes. A reminder for the late summer walk, the early autumn sealing and the spring check covers most of the year. The reminder works best when it is set to a date the homeowner will actually see.
Sources
- Colorado State University Extension, PlantTalk: Boxelder bugs (extension.colostate.edu)
- Colorado State University Extension, IPM pages on termites (agsci.colostate.edu)
This guide is general information for Boulder County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.