Globs of boxelder bugs

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Our lab and county extension offices around the state were getting swamped with calls about boxelder bugs when we had that warm spell towards the end of March. Many people complained about big disgusting globs of these black and red bugs appearing on the outside of their homes. I have globs of them too, but I don’t find these fall invading insects nearly as obnoxious as Asian lady beetles, as they are much more polite house guests. They don’t stink, they don’t bite and they pretty much keep to themselves. Many of the ones that come into my house die in the light fixtures. Boxelder bugs are harmless: they do not bite; they do not eat fabrics, stored foods, wood or pets; and they will not lay eggs in the house and multiply there.

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Globs of boxelder bugs on my house.
Photo credit: Howard Russell

During the summer, boxelder bugs feed on the flowers and seed pods of female boxelder trees. Boxelder bugs invade our homes and other structures in the fall of the year looking for dry, protected sites (attics, wall cavities) in which to spend the winter. They can become quite numerous on the south side of homes where they congregate in the warm autumn sun. In homes invaded by boxelder bugs, it is very common and likely that one will continue to see them throughout the winter. Once they are inside, there is not much one can do to completely get rid of them.

The best long-term method of controlling boxelder bugs is to prevent their entry, and if possible, the removal of any nearby female boxelder trees. Sealing exterior cracks and holes with caulk can help reduce the number of bugs that find their way inside walls and attics. There is very little that can be done once the bugs are inside the walls. Even aggressive and costly insecticide applications may not be effective, because it is nearly impossible to treat every hidden area that may be harboring insects. A vacuum cleaner is a pretty effective method of removing the sluggish, slow moving bugs from the house. Spraying the outside walls of homes, especially the south and west facing walls, with insecticides in September can help reduce the number of these insects entering homes. Be sure the insecticide is registered for this use. The spray should be applied when the first boxelder bugs are noticed congregating on outside walls. Be sure to read and follow all the instructions and safety precautions found on the pesticide label before using any pesticide.

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