Those red and black bugs clustered on your siding or stacked up in the branches of your yard trees aren’t subtle. Boxelder bugs congregate out in the open, and their numbers can build fast. Knowing what they’re actually feeding on tells you a lot about why they’ve landed on your property specifically.
The Boxelder Tree: Its Primary Food Source
The name gives it away. Boxelder bugs are built around boxelder trees (Acer negundo), a fast-growing maple that’s spread widely across Washington and the rest of the Pacific Northwest. They feed by piercing into seeds, leaves, and seedpods to pull plant fluids out directly.
Female trees are the real draw. Female boxelder trees produce the dense seed clusters these bugs depend on most, and populations follow that food source closely. If there’s a seed-bearing female in your yard or on a neighboring lot, expect numbers to build there from late summer through fall, right as bugs start scouting for overwintering sites. Male trees don’t produce seeds, so they rarely pull anywhere near the same concentration of activity.
Do Boxelder Bugs Eat Other Trees? (Maple, Ash & Fruit Trees)
Boxelder is their first choice, but they’re not exclusive about it. Box elder bugs on maple trees are a familiar sight in Washington yards — silver maple and red maple both draw feeding activity. Ash trees show up on the list too, even though they’re in a completely different botanical family.
Fruit trees are worth knowing about. Apple, cherry, and plum can pull in feeding clusters during peak season. The damage tends to be cosmetic: pitted skin, small scarred spots on developing fruit. Young growth on smaller trees takes it harder than established ones. If your yard mixes these species close to a boxelder or maple, don’t expect activity to stay contained to just one tree. As populations build through summer, they spread across available food sources.
What Do Boxelder Bugs Eat in the Garden?
When primary food sources run short, they shift to low-growing plants. Strawberries, grapes, and soft-fruited plants can attract them. They feed the same way they do on trees, piercing the outer skin to access plant juice, and the damage shows up as small discolored spots that are easy to miss early on.
Seedlings near host trees are also vulnerable in late summer when populations are peaking. Feeding concentrations tend to cluster in the warmest parts of the yard, particularly along south-facing walls and fences near a host tree. Once they find a spot that offers food and warmth in the same area, they don’t move far.
Established plants usually handle garden-level feeding without lasting damage. Young plants in tight clusters are a different story. One season it’s dozens. By the next fall, Washington’s warm afternoons can push numbers considerably higher if the pressure isn’t managed.
What Do Boxelder Bugs Eat in the House (and in Winter)?
Inside your home, essentially nothing. When boxelder bugs move indoors in fall, they’ve already shifted into a semi-dormant state. They’re not hunting food sources. They’re after warmth.
They settle into wall voids, attics, and insulation to wait out the cold months. They’re not chewing your framing or getting into stored food. The issue isn’t what they’re doing inside your walls. It’s how many of them are in there doing it.
A large boxelder bug infestation creates real problems despite the lack of feeding activity. Reddish stains show up on walls and fabric when bugs are crushed, and at high numbers they become hard to avoid. When spring warms things back up, they’ll push out through baseboards, window frames, and vents and head toward outdoor host trees.
Are Boxelder Bugs Harmful?
They don’t bite and they don’t sting. Boxelder bugs get mistaken for something more threatening because of how they look and how many show up at once, but the actual harm is in the numbers, not in what any individual bug does.
Tree damage from feeding is usually manageable. Boxelder bug eggs hatch in spring on host trees, and nymphs begin feeding on new growth almost immediately. A healthy, well-established tree typically handles that without much visible impact. Trees that are already stressed, or ones that absorb heavy populations year after year, can show more noticeable scarring over time.
Numbers are the real problem. Once populations go unchecked, getting rid of boxelder bugs becomes urgent in a way it wasn’t the season before. Spiders and some bird species will prey on them, but not at a rate that makes a real dent in a large population. A significant infestation doesn’t manage itself.
Treatments applied before they move indoors in the fall work considerably better than treatments after they’ve already settled into your walls for winter. That timing matters more than most homeowners realize until they’ve dealt with it the hard way.
Seeing Boxelder Bugs in Your Home? Natura Can Help
If there’s a female boxelder tree in your yard or a neighbor’s lot, the right time to act is before populations push indoors in fall. Once they’re settled into your walls for winter, the job is a different conversation entirely. Natura Pest Control treats the exterior perimeter and surrounding host trees before numbers peak. Contact Natura today to schedule treatment before fall activity picks up.