Are Cluster Flies A Problem?
You see it every year around mid to late August, flies gather around screen doors and inside windows searching for warmth. The most common of these flies is the Cluster Fly. They tend to be larger than the common housefly and are dark gray in color. They hibernate in the house structure through the colder temperatures but will emerge from hibernation through warm spells, filling windows with their sunlight dances.
The good news about Cluster Flies is that they are harmless to humans and will not destroy property. Also, they do not breed while indoors, despite their numbers. The cheapest means for control is the good, old fly swatter. The Cluster Buster can hold up to 1000 flies. Pest strips also work well. For large swarms, a vacuum cleaner can be used for removal from screens and windows. Insecticides may also be used to control these flies, but ask yourself if it is really worth dealing with a poison to control an extremely harmless pest. If you do decide to use insecticides, be sure to follow the instructions and cautions on the label.
To help minimize the number of flies that can enter into your home or cabin through the fall, make sure that the screens around windows and doors are tight fitting and free of holes or tears. A finer mesh screen may be needed to prevent them from entering. Also, since flies are attracted to the warmth of a house, minimizing the amount of time that doors are left open will help out considerably.