Q. We have an annual problem with what we think are boxelder bugs. Every fall they end up in the house. Last year, we vacuumed up over 100! Why are they coming inside?

A. Like most living things in the fall, they’re looking for a warm spot in which to spend the winter. Since Florida is a long way for a bug to fly, they figure your house is the next best thing! As you know, boxelder bugs are pretty distinctive in appearance. The adult is about 1/2 inch long and is black with red-orange lines on the back and wings, and red eyes. Nymphs are mostly bright red.

Boxelder bugs are outdoor insects that feed on the female boxelder tree, and occasionally on silver maples. They can build up to high numbers on their host plant. Both adults and nymphs feed only on the leaves and seeds of the female (pod-bearing) tree. Male boxelder trees are not affected. Boxelder bugs use their sucking mouthparts to suck juices from foliage and seeds. They don’t do any significant damage to the tree; their real impact is when they try to move indoors in the fall.

Like other fall-invading insects (Asian lady beetles, stink bugs), the boxelder bugs leave their trees in the fall and look for a nice, protected place to spend the winter. It’s often easy to control these pests before they move indoors in the fall. They tend to cluster (sometimes by the thousands) on the sunny, south sides of buildings or on lower tree trunks just before they disperse to seek overwintering sites. At this time they are susceptible to pesticide spray. Once boxelder bugs are inside, they are difficult to control since they can be hiding just about anywhere indoors. They often end up in attics but can be in wall or ceiling voids, behind window or door frames, behind baseboards or drapery, in cracks and crevices.

Boxelder bugs make their presence known again in the spring (or on warm winter days) when they come out of hiding and look for ways to get back outside. They have wings but rarely fly. Boxelder bugs can stain fabrics with their fecal droppings. They can usually be removed with a vacuum but be forewarned that they can give off a foul defensive odor if crushed. They sometimes nip people if handled.

If you (or your neighbor) have a female boxelder tree, you should make sure that all vents, attic louvers, screens, etc, are in place and in good repair. Any openings on the outside, such as around electrical or plumbing conduits, should be caulked. Colonial can handle that job for you. Our technicians know how to find and seal all of those openings that a bug could use. We can also do an exterior perimeter treatment of your home that will kill the boxelder bugs before they can get indoors. You can help reduce the population by removing piles of leaves, debris or building materials near the foundation that the bugs use for hibernating sites. Also clean up last year’s fallen boxelder seeds that the bugs feed on in the spring.

Boxelder trees can be sprayed during summer to kill the bugs when they are actively feeding. Unfortunately, there is no permanent control for invading boxelder bugs. Many people who have the problem year after year end up removing the offending tree. Sometimes the boxelder tree is on your neighbor’s property. In that case, you should talk to the neighbor. He may be having the same problems with overwintering bugs, but may not realize that they’re coming from his tree.