Fall Invaders-- Are You Ready?

Features - Occasional Invaders

As summer winds down, it means certain pests are going to be looking for places to overwinter. Are you prepared for the calls?

August 16, 2013

In a matter of weeks, we’ll be relieved from swatting away mosquitoes during backyard barbeques. But that only means a new pest threat is ready to rear its head — pest management professionals know that overwintering insects and pests will be searching for ways to enter homes and buildings, seeking shelter to wait out the cold winter months.

As these pests look for harborage points that remind them of shelters found in nature — think cracks in cliff faces, openings in trees, underneath tree bark, etc. — their goal is to find warmth. This means they generally can be found on the southeast side of a house or building, which generally tends to be warmer. They can enter a structure through gaps and cracks around windows or doors, and where siding meets the foundation or roof. Attics and chimneys are notorious for being access points for all sorts of pests, from mammals to overwintering insects. What follows is an overview of the typical pests found in homes during the fall and winter months, and some tips to keep them at bay.

Brown Marmorated Stink Bugs.
These insects were first introduced into the United States in the 1990s in Allentown, Pa. Hailing from Asia, these pests have become an agricultural pest, causing damage especially to fruiting trees such as apples, peaches and pears. Their piercing-sucking mouthparts are used to pierce the fruit when the fruit is young, and as the fruit grows, the blemish becomes a bigger portion of the fruit. The fruit is usually then unable to be sold in grocery stores. For homeowners, they often invade the living space, a few at a time, throughout the fall. True to their name, the bugs cause an unpleasant odor when threatened or crushed.

BoxElder Bugs.
Boxelder bugs are native to the United States. They overwinter inside buildings, and when they first come out of a building, they feed on low vegetation. After a few weeks they start to mate and then lay eggs. Often, in late spring and summer, people will see large clumps of the boxelder bug nymphs under potted plants, beneath gutters, under flashing, in umbrellas and within other tight areas in the yard. Generally, boxelder bugs stay within a few blocks of their overwintering site, but they may travel as far as two miles.

Asian Lady Beetle.
This pest is more commonly known as the ladybug. The name “ladybug” is a misnomer, as these creatures are actually beetles.

There are lady beetles that are native to the United States, but by far the most common invader of buildings is the Asian lady beetle, an introduced species. This beetle was introduced into the United States to control pests on pecans and apples. They feed on aphids and scale insects, so controlling aphids or scales in the immediate area may help prevent a larger population. The larvae of the Asian lady beetle look very different from adults, as they tend to appear somewhat worm-like, often with spikes along their bodies.

Cluster Flies.
Cluster flies are large, slow flies that are often seen along windows in the spring, attempting to exit a structure. Often, people do not realize that cluster flies have taken up residence for the winter until their reemergence in the spring. They are thought to have originated in Europe and subsequently brought to North America. Cluster flies are parasites of earthworms, but eliminating earthworms will not resolve a cluster fly issue.

Adult cluster flies lay eggs in the soil near where earthworms are likely to be, and the maggots hatch and burrow themselves into the earthworm, developing there. These are especially an issue in the Northeast and may emerge in ski cabins when the heat is turned up. Cluster flies are attracted to light when the temperature is above 50°F, and are conversely attracted to dark areas and other flies when the temperature is below 50°F.

What To Do.
While these insects typically do not cause structural damage, they are generally considered a nuisance — and providing a pest-free home or work environment is the goal for PMPs. Here are some prevention tips to remember when implementing an IPM approach:

  • Before the winter months approach, seal gaps around windows and doors, including garage doors. The best time for this is during the summer after pests have left their overwintering site, and before they come back for the next season.
  • Be sure screens on windows are in good repair and do not have any openings.
  • Look for areas where pipes and electrical or cable lines enter the building. Gaps around these areas should be sealed.
  • Look for openings around soffits, eaves, attic fans, windows and vents in the attic used for ventilation. Many times these areas are not screened, allowing overwintering pests inside.
  • Inspect chimneys. Be sure the damper is closed when not in use, and know that if you’re dealing with a wood-burning fireplace, lighting a fire may discourage the insects using the chimney as an entry point.
  • Vacuuming is the best way to eliminate the insects once they are inside.
  • Tell customers that using “bombs” to treat the inside of a house can backfire — they may end up with dead insects still inside the walls, which then attract secondary pests, such as carpet beetles.

Exterior treatments around the exterior of the home may reduce the population of these overwintering pests, but they will not eliminate them completely. Taking the above proactive steps can reduce the presence of overwintering pests and will position you to be better prepared to combat pests when temperatures warm. A little work in advance can go a long way to stop these fall invaders.

The author is a technical specialist and board certified entomologist with Western Pest Services, Parsippany, N.J. She can be reached at