No Vacancy: Keeping Boxelder Bugs Out This Fall
As autumn brings cooler nights and shorter days to Vancouver Island, many of us start spending more time indoors. Unfortunately, some insects have the same idea.
One pest you may notice gathering on sunny exterior walls, around windows or even inside your home or business this fall is the boxelder bug. These distinctive black-and-red insects are primarily nuisance pests, but when dozens—or hundreds—begin congregating around a building, they can quickly become frustrating.
Fall is an especially important time to watch for boxelder bugs because they begin searching for protected places where they can spend the winter. Understanding what they are, why they are attracted to certain properties and how to keep them outside can help prevent a much bigger nuisance later in the season.
What Are Boxelder Bugs?
Boxelder bugs (Boisea trivittata) are true bugs known for their habit of gathering in large groups, particularly during the fall.
Adult boxelder bugs are approximately 12 millimetres, or about half an inch, long. Their bodies are mostly black with distinctive reddish-orange markings. Adults have red or orange lines along the edges of their wings and behind the head, while their overlapping wings create an X-like shape when viewed from above. Young boxelder bugs, known as nymphs, are smaller and often appear bright red with darker markings as they mature.
The good news is that boxelder bugs are generally considered nuisance pests rather than destructive ones. They don't typically damage buildings, furniture or structural materials, and their feeding usually causes little noticeable damage to trees.
That doesn't necessarily make sharing your property with hundreds of them pleasant.
When crushed, boxelder bugs can produce an unpleasant odour. They may also leave stains on curtains, walls and other light-coloured surfaces.
Why Do Boxelder Bugs Appear Around Buildings in the Fall?
During the warmer months, boxelder bugs generally live outdoors around their food sources.
As temperatures drop in the fall, adult bugs begin looking for sheltered locations where they can overwinter. Cracks in siding, gaps around windows and doors, wall voids, attics and other protected parts of buildings can provide exactly what they need.
This is why autumn can be prime boxelder bug season around homes and businesses.
On sunny autumn days, you may see large groups gathering on warm exterior surfaces. Buildings with significant south- or west-facing exposure can be particularly attractive because those surfaces receive more afternoon sunlight and warmth.
Vancouver Island's transition from mild autumn afternoons to cooler nights can make sheltered buildings an attractive destination for overwintering insects. Even if the bugs aren't causing direct damage, their presence can become difficult to ignore.
Where Do Boxelder Bugs Live?
As their name suggests, boxelder bugs are strongly associated with boxelder trees, also known as Manitoba maples. Seed-producing female boxelder trees are especially attractive to them.
They can also be associated with other species of maple and occasionally ash trees. British Columbia's provincial household pest guide notes that boxelder bugs favour Manitoba maple but can feed on other maples and some fruit trees as well.
During fall, however, their priorities change from feeding to finding shelter.
They may congregate around:
Sunny south- and west-facing walls
Window and door frames
Rooflines and soffits
Foundations
Cracks in siding or masonry
Utility penetrations
Garages and storage buildings
Attics and wall cavities
Once temperatures fall further, the bugs that have entered a structure generally become inactive in their sheltered hiding places.
What Do Boxelder Bugs Eat?
Boxelder bugs feed primarily on plant material using piercing-sucking mouthparts.
They are particularly attracted to the developing seeds and seed pods of female boxelder trees. They may also feed on seeds from other maple species and can occasionally be found on ash trees and other vegetation.
Their feeding typically doesn't create significant damage to mature trees or garden plants. That's one reason boxelder bugs are usually classified as a nuisance pest rather than a serious landscape pest.
Importantly, they are not moving into your home because they want to eat your building. They're looking for a protected place to survive the colder months.
How Can You Tell if Boxelder Bugs Are Getting Into Your Property?
The easiest sign is seeing the bugs themselves.
Homeowners may notice clusters covering a sunny exterior wall on a warm October afternoon. Others discover individual bugs crawling around window frames, curtains or walls indoors.
Business owners may notice similar activity around exterior entrances, loading areas, window frames or warm sections of a commercial building.
Check carefully around potential entry points, including damaged window screens, door frames, exterior vents, gaps around utility lines and pipes, cracks where different building materials meet and openings around the roofline.
Seeing a few bugs outdoors doesn't necessarily mean you have a major problem. However, repeated clusters or significant numbers around entry points can indicate that bugs are actively attempting to find overwintering sites in the building.
How to Help Prevent Boxelder Bugs
With boxelder bugs, exclusion is one of the most effective strategies.
Inspect your property and seal accessible cracks and gaps before large numbers of insects can move inside. Repair damaged window and door screens, inspect screens covering vents and seal gaps around plumbing, cables and other exterior penetrations.
Weather stripping and properly fitted door sweeps can also reduce opportunities for insects to enter. Garage doors deserve attention as well, particularly where worn seals leave openings along the sides or bottom.
We recommend sealing exterior openings and repairing screens as key preventive measures against fall boxelder bug invasions.
If bugs have already made it indoors, avoid crushing them against walls, curtains or flooring because they can leave stains and odours. A vacuum can be useful for removing smaller numbers of insects indoors.
Because boxelder bugs hiding inside walls and other inaccessible spaces can be difficult to reach, prevention is generally much easier than dealing with an established overwintering population.
When Should You Call Pest Control?
A handful of boxelder bugs may be manageable with sealing, screening and physical removal. Professional help becomes worth considering when you're seeing large numbers of bugs, they repeatedly return despite preventative efforts, they're entering indoor spaces, or you're unsure where they're getting into the building.
Commercial properties can have an additional concern: even harmless nuisance insects crawling around entrances, windows, customer areas or workplaces can create an unwelcome impression for employees, tenants and visitors.
A pest control professional can assess where the bugs are gathering, identify likely entry points and recommend an appropriate management strategy for the property.
Fall is also an ideal time to act. Once insects have settled deep inside wall voids or other protected areas for winter, accessing them becomes considerably more difficult.
Seeing Boxelder Bugs Around Your Vancouver Island Property?
If black-and-red bugs are gathering around your home or business this October, they may be trying to make your building their winter home.
Sentry Pest Control can help identify the pest, assess potential entry points and recommend an effective approach for managing boxelder bugs around your property.
Taking action during the fall can help keep nuisance pests where they belong—outside.
Contact Sentry Pest Control today to arrange an inspection or learn more about protecting your Vancouver Island home or business from seasonal pests.
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