by David Moore
Manager of Technical Services and Board Certified Entomologist
As the days get shorter and the weather cools, several pests such as boxelder bugs, brown marmorated stink bugs, cluster flies, and multicolored Asian lady beetles (ladybugs), enter structures to overwinter. They typically occupy the wall voids of walls that receive the most sunlight, usually the south and adjoining portions of the east and west walls. In the spring, they leave the structure to feed, mate, and lay eggs. They typically use the same structure year after year.
Such pests can be a problem in the autumn, winter, and/or spring: Autumn when they invade structures to hibernate; on warm sunny, winter days; and again in the spring when they attempt to leave the structure.
Room-by-room Reinvasion Prevention
The rooms most likely to be invaded are those located on the warm side of the structure, typically the south wall and the southern portions of the adjoining east and west walls.
First, remove the pests with a shop vacuum (not for stink bugs) and immediately empty the vacuum into a plastic bag, seal the bag, and dispose of it in an outside trash can. If there are literally hundreds of pests in a room, then call a pest management professional for a one-time treatment of the room. After the pests are dead, vacuum them up without stepping on or crushing any because that could cause stains on carpeting. After the pests have been removed, the only procedure that should be done to prevent their reentry into the inside is to seal their possible routes of entry.
Use caulk and/or foam to seal cracks and crevices. For the smaller cracks and crevices, use caulk but be sure to use the kind that is flexible and that can be painted or use clear flexible caulk if you are sealing naturally finished wood or other surfaces that will not be painted. Expandable foam can be used to seal the larger cracks and crevices that are hidden from view such as those around electrical boxes hidden by cover plates.
Areas to be sealed include:
- Window and door frames. Seal around the outside of the frame where the frame meets the wall.
- If you have double-hung windows that have window pulleys, seal the pulley holes with tape or stuff them with fabric (tie the end piece of fabric around the cord so that you can easily retrieve and remove the fabric in the spring).
- For electrical outlets and switch boxes, first be sure that the electricity is turned off, and then remove the coverplate, close the gap between the box and the wall, and replace the cover.
- For heating duct and air-return vents, remove the grate, close the gap between the duct and the wall/floor, and replace the cover.
- For light fixtures and ceiling fans, first be sure that the electricity is turned off, and then remove the fixture to the electrical box behind its base plate, seal the gap between the box and the wall, and then replace the fixture.
- Canister lights. Remove the decorative trim/plate and seal the fixture-to-ceiling junction, but do not seal the air vents on canister lights, they are required to allow heat from the bulb to safely escape.
- For skylights. Seal the junction of the skylight box or its trim with the ceiling.
- For baseboards, seal the junction of the baseboard to the wall.
- Door-to-doorframe gaps. Be sure that no air is coming in around the door (use weather stripping to close any gaps). You can either use your hand to go over the door-to-frame junction to feel for colder air coming in and/or at night with the inside lights on and the outside lights off, go outside and any light escaping to the outside indicates a gap to close.
- Thresholds. Close any gaps at the junction of the bottom of the door to the frame or step. Use a tight-fitting (no gaps) threshold plate and/or flexible seal for a tight fit; door sweeps can be used but don’t seal as tightly. Again, at night, no light should escape to the outside.
What Not To Do
- No attempt should be made to kill these insects in wall voids at any time! Why? The bodies of dead insects attract dermestid beetles (carpet beetles, larder beetles, etc.) because they are a favorite food of their larvae (immature stages). Dermestid larvae wander and will readily enter the living space, causing frustration and concerns. Dermestids are very difficult and sometimes impossible to eliminate in the exterior perimeter walls because the insulation present usually prevents pesticide from reaching them.
- Be patient and wait until it gets warm in the spring, then they will leave your home on their own. And no, overwintering pests do not reproduce while overwintering, they wait until they leave your home for such activities.
Doing the sealing as outlined above will reduce the entrance of colder air into your home in the winter and the loss of cooler air to the outside during the warmer months of the year. This will increase the energy efficacy of your home and save you money.