Tree Service Blog

Box Elder bugs
Boisea trivittatus

Boxelder bugs, Boisea trivittatus, is a well-known nuisance insects in the Pacific Northwest. We generally do not notice them in the summer months, as they live quietly in Box Elder or Maple trees. They only become an issue during the early spring or fall, when they can envelop buildings in swarms, and get inside homes and work places.
There are two kinds of Box Elder bugs in the U.S. The Eastern and Western, found west of Nevada. In the spring eggs are laid on Box Elder and Maple leaves, (Box Elder, being a type of maple tree). Box Elder bugs develop throughout the summer, living in the Box Elder or Maple trees. Box Elder bugs are brownish-black and about 1/2 inch long. They have three red lines going down their bodies. Young bugs resemble adults except they are redder and have no wings. The immature bugs feed mostly on Maple and Box Elder seeds, and the adults feed mostly on the leaves, flowers and seeds, causing no significant damage.
Box Elder bugs like to spend the winter in protected warm places. In the fall they will swarm to (generally) light colored, south or west facing walls of buildings and look for cracks and crevices in walls; window and door casings; in and around building foundations; and inside houses. They particularly like stone, masonry or other rough surfaces. They have been found sleeping in the crevices of rough bark trees, like Douglas fire, as well a rocky out crops. In the early spring, warm sun on their hiding places will wake the insects up, and they begin to crawl out and prepare for the coming season. As soon as Maple and Box Elder trees begin to put on their leaves, the Box Elder bugs will leave the warm places and retreat to the trees.
Box Elder bugs are harmless to property, and people, and even the trees they live in They do not feed on furniture, or wood siding or other plants around the house. They do not bite or sting people or animals. They can, however stain walls, or siding with their excrement.
Do what you can to prevent these nuisance pests from entering the inside of homes and offices. Repair or replace any damaged window or door screens. Seal areas around utility pipes or wires coming into the building. Make sure weather striping is in good shape around doors and windows. Move piles of wood or other tempting, warm hiding places that are too close to your home. If you are going to repaint your home soon, pick a darker color, and maybe plant a tree to shade the sunny area of your home. Treating for these pests on the outside of your home is virtually ineffective. Once inside, vacuuming the critters will help, but be sure to take the bag out side, as soon as you are finished.