By Nick Dunn

Boxelder bugs, often called maple bugs, have become an unwelcome nuisance across Flagstaff County this fall. They are covering sunny walls, gathering around doors and windows, and entering into buildings. These small black-and-orange insects are not dangerous, but their numbers have reached levels not seen in several years. Many residents have asked why they are so bad this year, how long they will last, and what can be done to control them.

Maple bugs are native to North America and a familiar part of prairie life. They feed mainly on the seeds and leaves of boxelder and other maple trees. In most years, they remain in low, manageable numbers. The insects overwinter as adults, sheltering under tree bark, in organic matter, or inside buildings. In spring, they emerge to lay eggs on young leaves and developing seeds. During hot, dry summers, they can complete multiple generations, leading to the large late-summer and fall populations we are currently experiencing.

This year’s outbreak can be traced to favourable weather and growing conditions. The warm, dry summer allowed more eggs and nymphs to survive, while last winter’s mild temperatures helped adults overwinter successfully. At the same time, boxelder and maple trees produced a heavy seed crop, providing abundant food. With high survival rates, plentiful food, and hot weather, populations can increase rapidly.

As fall progresses, maple bugs instinctively search for warm, sheltered places to spend the winter. They often gather in greatest numbers on sunny south or west sides of buildings. From there, they look for any small opening to squeeze into wall cracks, attics, or basements. While they do not bite, chew wood, or damage structures, they can stain walls and fabrics and can make an even bigger mess when crushed. For this reason, residents should avoid crushing them indoors. Instead, use a vacuum or sweep them gently into a container for disposal.

The sheer number of bugs this year has made them a major nuisance across Flagstaff County and surrounding areas. Fortunately, the problem is temporary. Once the first hard frosts arrive, the insects become sluggish and die off in exposed areas. I have already started to see them become docile with the cooler nights. Only a portion of the population will successfully find overwintering shelter, and by late fall, outdoor activity drops sharply. During the winter, some may reappear indoors during warm spells, but they do not reproduce inside homes and will eventually die off without access to food.

Whether next year will be as bad depends on several factors. A cold, harsh winter would reduce survival, and a cooler, wetter summer in 2026 would limit population growth. However, if Alberta experiences another hot, dry year and boxelder trees again produce abundant seeds, another heavy infestation could occur next fall.

Residents can take several practical steps to reduce infestations. Prevention is the most effective control. Sealing cracks and gaps around windows, doors, vents, and siding will keep bugs from entering buildings. Replacing damaged window screens, installing door sweeps, and caulking around utility openings all help. Outdoors, using a strong jet of water or a light soap-and-water spray can dislodge clusters from walls without harsh chemicals. Spray Nine is also effective for cleaning and removing maple bugs and stains. It rinses off more easily than soap solutions and removes the dark fluid they release which is a defensive mechanism and fecal matter. Keeping yards free of leaves and organic debris will also help reduce next year’s populations be removing areas for them to overwinter.

Chemical insecticides can be used as a last resort but should always be applied according to label directions. Spraying foundations and lower walls in late summer before bugs begin to cluster can provide short-term relief, but benefits are temporary and overuse can harm beneficial insects, pets, and yourself. Indoors, vacuuming remains safer and more effective than spraying. Maple bugs are primarily a nuisance rather than a threat. With some preparation and patience, their numbers will decline as the weather cools. Residents who take time now to seal entry points, clean up potential habitats, and avoid crushing the bugs will be better prepared to prevent future infestations.

Nick Dunn is Flagstaff County’s Agricultural Fieldman. He can be reached via email at: ndunn@flagstaff.ab.ca or by phone at: 780-384-4138.