I live in a basement level apartment. It seems like every fall we start seeing these really big cockroaches which I’ve been told are American cockroaches. I find a couple of them inside every day. Why do I just have them in the fall? S. T., Lowell, MA 

It’s not your imagination. American cockroaches can appear in fall, when populations are at their highest level. These cockroaches have only one generation a year, meaning that instead of hatching throughout the year, egg cases are laid and hatch only in early summer. The cockroach nymphs grow throughout the summer. In the fall there are a large number of full-grown American cockroach nymphs, plus the adult cockroaches that are still alive.

Because there are so many nymphs trying to find food and hiding places, they move out into new areas in the fall. This is the best time of year to try to control American cockroaches, especially with baits, but it’s a narrow window of time. Once the weather turns too cold, the nymphs become less active, feed less, and move into hiding places for the winter.

Where are the Cockroaches Coming From?

In your case, it’s important to find the source of the cockroaches which is almost certainly outside of your apartment. American cockroaches have different habits than our more common (and smaller) German cockroaches. We find American roaches mostly in commercial accounts where they usually occupy the basement or lowest level of the building.

American cockroaches are also the most common cockroaches infesting sewers and landfills. When American cockroach nymphs migrate out of the sewer system, they often enter buildings through floor drains or sewer line breaks, or they can simply exit to the street through vent holes in manhole covers (see Cockroaches From Sewers).

Give us a call. Our technicians can inspect your apartment and surrounding area to determine the source of your cockroach problem (could even be the laundry room in your building). Control can be complicated if the source of the cockroaches is not on your property, but we can definitely apply a barrier treatment to keep them out of your apartment.

Photo: Clemson University – USDA Cooperative Extension Slide Series, Bugwood.org – See more

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