Overwintering Pests in Your Home: What You Should Know

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Black and red beetle

What are overwintering pests?

Overwintering pests include several different types of insects that seek shelter inside structures, such as homes or businesses, during the colder months of winter. Once established, these pests can often show up in large numbers, both outside and inside homes. Homeowners may experience an influx of these pests moving towards their home in the fall, and then again in the spring when they emerge from their hiding spots and start working their way back outdoors. As with most insects, effective control is best achieved through ongoing, preventative exterior pesticide applications designed to reduce overwintering pest populations outside, so that they are much less likely to find their way inside.

Although others exist, some of the most common overwintering pests include boxelder bugs, Asian beetles, stink bugs, and cluster flies.

1. Boxelder Bugs

Boxelder bugs are a black, flat, oval insect with distinct reddish or orange markings on their backs. Adult boxelder bugs are generally about ½” long. They often become a nuisance when they invade homes or other buildings in the fall and then emerge from their harborages in the spring. Native to the western United States and named after the fact that they are routinely found on or around boxelder trees, boxelder bugs are now commonly found throughout the U.S.

To prevent boxelder bugs from invading homes, it’s best to practice exclusion practices such as:

  • sealing holes or cracks around doors, windows, utility lines, and other penetrations.
  • routine pesticide applications around the outside of the home.

Once established inside, remediation can be a slow process. It is generally unadvisable to treat or kill them inside wall voids or cavities where they may be harboring. Because they will emerge from their hiding spots naturally during the spring and into the summer, the best approach often includes:

  • an ongoing vacuuming regimen where the bugs can be captured and discarded outside away from the home.

Thereafter, to prevent future reinfestation into this same area,

  • all entryways should be sealed as much as possible.

2. Asian Beetles

Asian lady beetles may often be found clustering on or around homes or other buildings in large numbers during the fall in search of protected areas to ride out the winter. Feeding primarily on aphids or other insect plant pests, these insects are often considered beneficial to many farmers or gardeners, but they may also infest certain fruits such as apples.

Asian beetles can become a nuisance inside homes, particularly when they appear in large numbers. Although they do not sting, destroy fabrics, or cause property damage, they can bite hard enough to pierce through the skin which may cause minor agitation or discomfort.

As with boxelder bugs,

  • vacuuming and removing Asian beetles inside the home is often a better approach than attempting to kill them.
  • exterior pesticide applications, particularly in the fall, will help keep outside populations down and reduce the likelihood of ongoing presence inside the home.

3. Stink Bugs

Stink bugs are another overwintering pest that can show up in large numbers inside or outside a home. Adult stink bugs generally emerge in May and begin to lay eggs soon thereafter. In most areas, stink bug populations are often highest from August through October before the adults start seeking shelter inside structures. Stink bugs will commonly be found gathering in high numbers on the sunny side of homes or other buildings, particularly on warm winter days.

To prevent stink bugs from entering your home,

  • it is especially important to make sure all doors and windows are adequately sealed.

Once inside the home,

  • physical removal is often recommended as opposed to pesticide intervention, as stink bug biology sometimes limits the effectiveness of insecticides.

4. Cluster Flies

Cluster flies are black flies that are a little larger than common house flies. In areas where they are present, they may be found accumulating in large clusters inside attics throughout the winter. Laying their eggs in the soil around homes and other buildings, adult cluster flies typically emerge in August and September and begin their search for winter shelter.

Outside pesticide applications for cluster flies are generally most effective during this time. Piles of dead cluster flies are often found in the spring. As with other overwintering pests, clusters are commonly found in sunny locations outside buildings.

How To Prevent Overwintering Pests

In addition to eliminating entry points where adult overwintering pests might look to gain access to the home, the most effective way of dealing with overwintering pests is prevention. Routine pesticide applications, with a heavy residual treatment in the late summer or early fall, will keep most overwintering pest populations to a minimum.

Consider the services of a licensed local pest control professional for pest control treatments.