3a8b3 boxelder bug adults and nymphs1
Boxelder Bug adults and nymphs

Mounds of writhing blackish and red insects, in mid-summer to early fall, are often an indication of a Boxelder Bug infestation. Although they are a nuisance, the Boxelder Bug does not actually harm the areas they congregate and because it may be a temporary stopping location, the bugs may be gone in just a couple days. This is simply the time of year when the insect has reached the adult stage and is looking for warm, sunny locations to overwinter. Boxelder Bugs disappear with cold weather and overwinter in their chosen host. But the sight of so many insects can be very disconcerting for homeowners.  Although the preferred location for overwintering is the base of the host tree, Boxelder Bugs may also overwinter in nearby locations. This includes rock walls, firewood piles or even under the siding of buildings or houses. It is possible that the Boxelder Bug will choose to go inside a home or foundation and overwinter. When this happens, there are treatment options.

There are a few methods for managing Boxelder Bug infestations. Although removing any Boxelder trees near the property will eliminate their primary host plant, this does not always affect the likelihood of future infestations. If removing the host tree is not an option, ensure all entryways into the home are properly sealed. If the Boxelder Bug has already infested the home, vacuum the pest and empty the vacuum cleaner outside. Otherwise, the bug may crawl out of the vacuum cleaner and re-infest the home. There are insecticides that can be used on the exterior of a home, which prevent the Boxelder Bugs from entering a house. Read the insecticide label thoroughly, to insure its being used correctly. Often, the Boxelder Bug chooses to gather on a warm, sunny outside wall or firewood pile. If this occurs, spray the area with a strong blast of water. The bugs will dissipate, but possibly only temporarily. They may return to take advantage of the warm, sunny area. While the Boxelder Bug is bothersome, it does not bite or carry any known diseases. Its appearance in the fall is temporary and does not necessarily reappear in the same locations year after year. Having an infestation one year, does not guarantee a problem the next year.

As its’ name indicates, the Boxelder tree is the Boxelder Bug’s favorite host. The Boxelder Bug is also attracted to other tree varieties, including Silver Maple, Ash, Apple and Plum trees. The nymph stage is when tree damage can occur. This is when the insect hatches from freshly laid eggs in late spring to early summer. The Boxelder Bug nymph immediately begins feeding on the seeds and new leaves of their host tree. Symptoms of their feeding include leaf deformities and blemishes on the tree’s fruit, where the nymph has sucked the plant juices of their host. Damage is ordinarily minor, unless a very large infestation is present. The Boxelder Bug nymph grows rapidly on the host tree throughout the summer as it feeds continuously. As the season progresses, the Boxelder Bug adult leaves the host tree in search of a place to overwinter. This is normally when large numbers of insects are seen and become an annoyance for people. The Boxelder Bug cycle starts all over the following spring, when the adults leave their winter location in search of a host tree to lay eggs.  

If you suspect a Boxelder Bug infestation and would like to discuss options, please contact the Plant Health Care department at KTS. For information on other insects in the Chicago area, visit the pest control page on the KTS website.

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