Indoor fly infestation

Asked February 14, 2018, 6:57 PM EST

Over the last few months we have had an infestation of house flies in our family home which was built in the late 80s.They were first noticed in the family room next to the kitchen on the main floor, and lately they’ve been upstairs in our bedrooms. We cannot associate anything with the flies...food, smells… We are hesitant to hire a pest control to spray inside the house. Can you provide any information as to how this infestation might have started and what we can do about it, hopefully without resorting to chemicals? Thank you

Benton County Oregon

1 Response

Flies in homes are usually accidental invaders that were overwintering in wall spaces, attics, etc. The recent string of warm days may have encouraged them to become active. But instead of moving outdoors, they entered your warm house!

Here's some information on cluster flies from Penn State Extension that you may find helpful. Cluster flies are a little different from house flies as they tend to fly slower and cluster together as they fly (compared to houseflies which generally are more solitary and faster).

Both houseflies and cluster flies can be physically removed. If swatting them is difficult or undesired, try using the extension tube of a vacuum cleaner to remove the adults. Empty the canister outside to avoid letting them loose into the house again. As we move into this cold snap, you will likely see less flies.

To prevent the problem from reoccurring, take some time this summer to seal any exterior cracks (like around windows, etc.) and make sure your window/door screens are in good shape.

Hope this helps and please feel free to let me know if you have any further questions!

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