By Karen Johnson, University of Minnesota Extension
As the weather begins to cool, several insects begin searching for a place to overwinter. Some insects, including the boxelder bug and lady beetles, become a nuisance as they decide to move into our homes. Now is the time to prepare to help minimize the problem later.
Adult boxelder bugs are about a half-inch long, black with orange or red markings, including three stripes on the prothorax, the area right behind the head. Their wings lay flat over their bodies, overlapping each other to form an ‘X’. The immature nymphs are 1/16th-inch long and bright red when they first hatch. As they grow older and become larger, they are red and black.
Here are some things to keep in mind when trying to prevent boxelder bug entry into your home:
- Repair or replace damaged window and door screens.
- Repair or replace damaged screens in roof and soffit vents, and in bathroom and kitchen fans.
- Seal areas where cable TV wires, phone lines, and other utility wires and pipes, outdoor faucets, dryer vents and similar objects enter buildings.
- Seal with caulk or for larger spaces use polyurethane expandable spray foam, copper mesh, or other appropriate sealant.
- Install door sweeps or thresholds to all exterior entry doors.
- Install a rubber seal along the bottom of garage doors.
You may want to supplement non-chemical methods with an insecticide treatment around the exterior of your home, especially if a large number of boxelder bugs are present and/or you have a history of boxelder bug invasions. The best time to spray is late summer and fall when boxelder bugs are first clustering around the outside of buildings.
You can treat your own home by using an insecticide labeled for the exterior of buildings. Examples of common names of active ingredients available to the public include: bifenthrin, cyfluthrin, deltamethrin, lambda cyhalothrin, or permethrin. Also be sure the product indicates it can be used on the exterior or outside of buildings. Look for this information under Directions For Use. Caution: Read all label directions very carefully before buying and applying any type of insecticide. Information on the label should be used as the final authority.
Once boxelder bugs are found in your home the best option is to physically remove them with a vacuum or a broom and dustpan. If this occurs during fall, check around the building exterior because they can often be found congregating in sunny or warm areas. If they are close to entrances, an insecticide may be required to prevent their entrance into a home.
Inside homes, insecticides are not recommended since boxelder bugs don’t live for very long. Remember that when boxelder bugs are active, they do not live indoors much more than a few days and do not reproduce inside. When they are emerging from the walls and other sites where they have been dormant during the winter, spraying insecticides does not prevent more from returning.