Winter is Coming

Features - Occasional Invaders

Fall is the time when overwintering pests begin making plans to survive the cold — and PMPs should start planning their control strategies.

September 30, 2015
Sandra Kraft & Larry Pinto
Room by Room sponsored by Zoecon

Editor’s Note: This article was adapted from Techletter, a biweekly publication from Pinto & Associates, Mechanicsville, Md. To subscribe, visit, or call 301/884-3020.

You know about occasional invaders — those outside perimeter pests like earwigs, pillbugs, millipedes and crickets — that occasionally find their way inside. There’s a subset of occasional invaders that can be called fall invaders. These are the pests that enter buildings in the fall as the weather cools, with the intent of finding a sheltered place to spend the winter.

Some of our most problematic overwintering fall invaders are the Asian lady beetle, brown marmorated stink bug, boxelder bug, elm leaf beetle, cluster fly and paper wasps.

These are also the pests that pest control companies get calls about in the spring when the intruders have suddenly reappeared indoors and are trying to sneak back outside. Unfortunately, the time to control those overwintering pests was the previous fall — it’s important for you and your customer to take steps this year before the pests begin to migrate indoors. So, we’re giving you plenty of advance warning. Now is the time to schedule those fall perimeter treatments and pest-proofing jobs.

Control Options. When fall invaders get inside, some of them will die fairly soon due to the drier indoor air. Others, though, will end up in the attic, behind baseboards, in wall voids, behind drapes (some of these pests can damage or stain fabrics)...almost anywhere. Because their hiding places are so scattered and so hidden, fall invaders are notoriously difficult to control once they are inside. In the spring, as the days get warmer (or sometimes on warm days during the winter), these pests become active again. They’ll leave their hiding places in large numbers, trying to find a way back outside. They’re often attracted to light coming from a window, or they may be seen crawling along baseboards or up walls.

An outside perimeter or barrier treatment is usually a pest control company’s first line of defense against fall invaders. The big selling point is that a perimeter treatment keeps the pests from getting inside in the first place so indoor control is not an issue. Plus, a perimeter treatment means no insecticide inside the home. Timing is critical. Treat too soon and the residual may be gone by the time the pests migrate. Too late, and they may have already begun their move inside. Schedule the treatment so that the residual lasts up to the first hard frost.

For those fall invaders that are plant feeders (elm leaf beetle, boxelder bug, stink bug), treating their host plants, or at least the trunks of trees, in late season can eliminate many potential migrators (be aware, though, that some states require a different license or certification category for this treatment).

Pestproofing. Along with a perimeter treatment, sealing openings that pests use to enter provides double protection against fall invaders. Pestproofing is usually the responsibility of the customer, but many companies offer this service as well.

Some pestproofing tips:

  • Caulk cracks around doors and basement or ground floor windows.
  • Make sure window and door screens fit securely and screen outside vents.
  • Install thresholds, sweeps and weather stripping on ground-level doors, including garage doors.

Perimeter Cleanup. When fall invaders are looking for a place to spend the winter, they are attracted to anything that provides shelter and moisture. When they find these conditions around a building’s perimeter, they are more likely to accumulate there and may eventually find their way inside.

To reduce the number of fall invaders around a foundation, your customer needs to keep the area dry and free of thick plants and shrubs and other pest hiding places. Getting your customer to take these steps first will make your perimeter treatment much easier:

  • Move wood piles, compost piles, piles of leaves or grass clippings, or stacked boards or stones away from the foundation.
  • Pull mulch away from foundation walls.
  • Remove grass, weeds and ground cover plants that touch foundation walls.
  • Drain standing water around the foundation.
  • Reduce outside lights, especially around doorways. Some fall invaders are attracted to lights.
  • Ventilate basements and crawlspaces to reduce moisture levels.
  • Trim any shrubs or tree branches that touch the roof or sides of the home/structure.


The authors are well-known industry consultants and co-owners of Pinto & Associates.