Controlling Overwintering Pests

Controlling Overwintering Pests

One of the benefits of the onslaught of winter, at least in parts of the country that have a true winter, is that mother nature will remove bugs from our lives until next spring arrives. However, that’s not always the case as some pest species have become more adaptable and have found ways to survive changes in temperature. These overwintering pests begin to seek shelter in warm homes and buildings when temperatures start to drop in fall months. Once they have secured an overwintering location indoors, which often goes unnoticed, they enter a state of diapause—hibernation triggered by adverse environmental conditions—until outdoor temperatures warm. Controlling overwintering pests requires identifying the pest, locating and sealing entry points, and exterior and interior treatments.

Common Overwintering Pests

As is true for all pest treatment programs, identifying the pest is the first step to controlling a potential infestation. The most common overwintering pests include Asian lady beetles, boxelder bugs, cluster flies, and stink bugs.

Asian Lady Beetles

These are not to be confused with the common and adorable ladybug. Asian lady beetles are an invasive species. They are similar in appearance to ladybugs but have a M-shaped marking on their head. These pests release an unpleasant odor and produce a yellow staining fluid when they feel threatened or are crushed. Thousands of Asian lady beetles can enter houses in the fall. They gravitate to warm areas in homes and structures hiding in cracks and crevices including under siding, in wall voids, and other protected locations.


Boxelder Bugs

Boxelder bugs are about ½” long and black with reddish-orange markings. These pests feed on the seeds of boxelder trees and are also found on maple and ash trees. They can become a big problem when they infest homes by the hundreds or thousands. Boxelder bugs enter homes at ground level or fly to higher locations. Once inside, they gather in walls and warm basements. Though they typically remain dormant in winter, they may become active on unusually warm winter days.

Cluster Flies

While they may look like houseflies, cluster flies are slightly larger and more sluggish. They are about ¼”-3/8″ long, dark grey, have gold hair, and a checkered pattern on their abdomen. The get their name form their tendency to cluster together before hibernating in winter. Large clusters of flies will huddle inside wall voids, attics and false ceilings. Cluster flies are commonly found in upper areas of buildings.

Stink Bugs

Another invasive species is the stink bug. These pests are identified by their shield-shaped body. They are pests of produce, but they can also be a problem for homeowners. In late summer, they begin searching for warm places to overwinter. Stink bugs get their name because they release an unpleasant odor when they are frightened or crushed. They can invade homes by the thousands and tend to stay in walls and attics until spring.

How to Manage Overwintering Pests

The best way to control an overwintering pest problem is to prevent them from getting inside homes in the first place. That’s not always an easy task since many of the preventative pest-proofing measures needed may require the cooperation of your customers. Managing overwintering pests will require a combination of pest-proofing, with your customer’s help, and the application of insecticides on the exterior and interior of their home. The more exclusion work you can do, the better. The following three steps are a good guide to controlling these nuisance pests.

1. Inspect & Pest-Proof: Prevention is Key!

The first step is inspecting and pest-proofing the structure. Since overwintering pests tend to gather on the sides of the house that receive the most sunlight, start the pest-proofing efforts there. Inspect the exterior of the home closely to find potential entry points.

The most common entry points overwintering pests use include:

  • Cracks, gaps, and holes in siding or the foundation
  • Holes around utility and electrical lines
  • Damaged door and window screens
  • Under and around window and door frames
  • Loose chimney flashing
  • Damaged or missing screens around soffit and attic vents

2. Exterior Treatment: A Thorough Perimeter Barrier Treatment in the Fall

After working on pest-proofing the structure, the next step is to focus on an exterior perimeter treatment. In early to late fall, a thorough perimeter insecticide treatment will create a protective barrier around the outside of the house. Concentrate on the sunny sides of the home since they will attract the most overwintering bugs. Ideally, you want to treat the home before pests begin entering. Rockwell Labs provides different options depending on if you are providing preventative services, fighting an active infestation, or if you prefer to use a natural or green insecticide versus a conventional product.

  • EcoVia EC: This botanical insecticide concentrate provides quick kill control and residual repellency. Apply to exterior surfaces, the foundation, and the band of soil surrounding the structure. EcoVia EC is a broad-spectrum product that has no pyrethroid or neonicotinoid use restrictions.  
  • EcoVia WD: Another EcoVia botanical product that provides quick control and residual protection. EcoVia WD wettable dust is a versatile product that can be used as a dust in cracks and crevices and as a liquid suspension on exterior surfaces. Apply as a liquid around the foundation and in any areas where overwintering pests congregate or stage along the structure. It’s great for dusting attics and potential entry points.
  • LambdaStar UltraCap: If you prefer to use a conventional product, or to get quicker control when pest populations are excessive, this micro-encapsulated pyrethroid will gain fast control and provide extended residual protection. Just be sure to note the pyrethroid label restrictions.
  • FenvaStar EcoCap: Another micro-encapsulated pyrethroid option for a perimeter barrier treatment is FenvaStar EcoCap. It will also provide both quick control and extended residual protection.
  • Try a Combination of Products: To get the greatest longevity, the ultimate killing efficacy, and the strongest repellency, tank mix EcoVia EC with a micro-cap pyrethroid like LamdaStar UltraCap or FenvaStar EcoCap. Tank mix applications must be made in accordance with the more restrictive of label limitations and precautions.

When applying a liquid treatment around the perimeter of a home, pay special attention to all visible cracks, crevices, gaps, window and door frames, eaves, porches, decks, patios, garages, sheds, and other areas where pests are active. Be sure to treat areas such as false shutters, window wells, underneath siding, around exterior light fixtures, and underneath dense bushes and shrubs.

3. Interior Treatment: To Control the Pests that Made it Indoors

After treating the structure’s exterior, treatment may be needed indoors if any overwintering pests are found inside. Once inside, overwintering pests can be difficult to control and hard to locate if they have settled into their hiding spots. Because their activity level is reduced when they are in hibernation mode, this limits their potential contact with insecticides.

An amorphous silica dust, such as CimeXa, is a great product for overwintering kill on the interior of structures. CimeXa is odorless and non-repellent, so insects do not avoid it and will continue to reside in the areas treated. Pests that contact CimeXa will die even if they do not move over the winter months due to rapid dehydration. CimeXa can be applied as a dust or liquid in attics, crawlspaces, around garage doors, under or behind exposed insulation, under siding, and other overwintering sites.

If you notice any stragglers that made it inside, it’s best to vacuum them up quickly and dispose of the vacuum bag. Discuss this with your customers as they are more apt to see them appear on walls, ceilings, and floors during unseasonably warm winter days.

What Homeowners Can Do to Help Prevent Overwintering Pests

Getting homeowners involved in the process can help to prevent future pest problems. Encourage your customers to get involved with pest-proofing their home by doing the following:  

  • Cutting back vegetation, leaving 1-2 feet of space between the exterior of their home and vegetation
  • Storing firewood at least 20 feet from the house and keeping it off the ground
  • Repairing or replacing worn seals and damaged screens
  • Reducing exterior lighting that could attract pests
  • Minimizing moisture around their property
  • Doing exclusion work where needed around their house that you were unable to handle

Overwintering pests can be challenging, but having the right plan will make your control efforts successful. By following this three-step process, you will be able to prevent overwintering pest problems in your customer’s homes and also get rid of any infestations that occur.