Fall Pests

With the change of seasons, comes the changing cast of pests. For more information on these pests, check under the insect or rodent links, or click on the links below. These are some of the main culprits on the ‘pest parade’ for the fall season.

Cluster flies

Cluster flies start around mid to late August. As many people living in the country have learned the hard way, flies that gather in windows, buzz around the lights and fall spinning to the floor are cluster flies. Their presence solicits anything from mild annoyance to putting a for sale sign on the front lawn!

Cluster flies enter structures in the fall in order to try and over winter. Once inside, while it is cold they remain dormant. Unfortunately on sunny days, even in winter, they will become active and end up coming out inside the house. They are often found at windows because the light from outside is attracting them. Late fall and early spring are when the flies tend to be most numerous in homes.

Box Elder Bugs

What is black and red and gathers in large numbers on the sunny sides of homes? The answer is boxelder bugs. Boxelder trees in the East are commonly called Manitoba or soft maples. These insects are a major pest of soft maple trees feeding primarily on fallen keys in the early spring and the newly forming leaves later on. Boxelder bugs only feed on the female tree. Female trees produce keys, the male trees do not. Like many other insects, they look for places to over winter and homes and other buildings provide an ideal location.

Paper wasps

Paper wasp colonies are peaking in size. These wasps will be looking for places to over winter. They often get up into the soffits and attics of homes.

Yellow jackets & bald-faced hornets

Yellow jacket and bald-faced hornet nests are reaching their maximum size. Large football nests seem to suddenly appear on tree branches, but in fact, have been building all summer. If you have yellow jackets going into the siding of your home, plugging the hole is often the worst thing that you can do as they may start coming out inside the house.

Pine seed bugs (Western conifer seed bugs)

Pine seed bugs, often called stink bugs, start looking for harbourage sites for the winter. They will crawl into gaps and attics of homes and sometimes come out inside the house where they will congregate on windows.

Lady bugs

Like cluster flies and pine seed bugs, lady bugs will enter homes in the fall to over winter. Since lady bugs are small, they can crawl in through tiny openings. Lady beetle numbers seem to be related to the degree of infestation of soya bean aphids on soya beans. Aphid populations are lower this year which may result in lady bug numbers being down. They usually appear around Thanksgiving when the crops are harvested.


The fall is the prime time for mice to enter structures. Preventative treatments and rodent control programs should be done at this time of year.

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