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Managing a Boxelder Swarm


Adult boxelder bugs are large black insects with reddish-orange markings on their wings (see photo). The immature nymphs have red as their dominant color.

A swarm of boxelders, a red insect
Photo Credit:
William M. Ciesla, Forest Health Management International,
Boxelder swarm

These bugs spent summer sipping on the sap of soft-wooded maples, including silver and boxelder maples. They didn’t damage the trees and most of us did not notice them.

But the warm, carefree days of summer are over and the bugs are desperately looking for heat. You can find them sunning themselves on the south- and west-facing sides of homes.

Boxelder bugs are fairly harmless. They don’t breed indoors and they won’t eat your food. They won’t bite your toes and they won’t eat your furniture. They are just looking for a warm place to spend the winter.

You can leave them alone and after a few hard frosts the problem is over.

If the bugs are causing you a major nuisance, consider spraying them with detergent. Mix three to five tablespoons of liquid detergent per gallon of water. Detergent sprays kill bugs that are sprayed upon and have no residual effect. Repeated detergent sprays will be necessary.

For severe infestations, toxic insecticides can be sprayed on and around the foundation of the home. Insecticides with synthetic pyrethroids are recommended since they work under cool temperatures. These include permethrin, cyfluthrin, and esfenvalerate.

The best defense is to “pest-proof” your home. Caulk any cracks along the foundation, doors or windows. Seal openings where utility cables enter the home. Screen any vents, and apply weather stripping on doors.

Any boxelder bugs that enter your home can be swept outside or vacuumed. Avoid squishing the bugs because their “juices” can stain fabrics. If vacuuming, empty the dust bag immediately to prevent bugs from escaping out of the vacuum.