Fungus Gnat Home Interior Infestation

Asked July 27, 2018, 3:51 PM EDT

Since the middle of May the first level of our home has had increasing numbers of fungus gnats on just about every window sill and on the bathroom floors. At first it was just a few gnats in a couple of windows but now 5 windows on the north side of our house have hundreds of gnats each every day. Most of the gnats seem to be dead but there are quite a few flying round the windows. We have no house plants in the house. Our house was built last year and completed on July 3, 2017. We never saw any gnats in the house until this problem started. Paramount Pest Control treated the drains and fogged the house but within days the gnats were back to what they were before. The next week Paramount came back and sprayed around the foundation of the house but this was the day before we had 3.5 inches of rain. Again, the gnats were unaffected. Our house has lawns around all sides with some mulched areas against the foundation containing various plants like roses, ornamental grasses, etc. My questions are: 1. Looking at the included photos, are they really fungus gnats? 2. Assuming that the gnats are getting in from the outside, what is the best treatment for getting rid of them long term? Thanks for any help with this problem.

Talbot County Maryland insect or spider id pest insects and mites

5 Responses

Our entomologist looked at your photos and thinks that these look too small to be fungus gnats and are just typical outdoor gnats that can swarm in clouds occasionally and drift inside on air currents either through screens or doorways.
They are more common and plentiful during wet weather like we've had and are having. You are finding them in windows because they are trying to get out and then dying there.
You need to stop spraying and treating (and we NEVER recommend fogging).
They are harmless (unlike pesticides) and are a temporary issue as they don't live long.
Simply vaccuum them up or wipe them away with a damp paper towel.

cm

Thanks for the quick response.
My experience with outdoor gnats is that they fly around your face and get into your eyes. The ones we have in our house do not fly near our faces, are not attracted to food at all and do not bite.
Also, we never have our windows open (due to allergies) and are careful about closing the exterior doors quickly. So how can we have thousands of these gnats around the windows everyday (we vacuum them up every morning). This has been going on for over 2 months now.
Can they be something else rather than outdoor gnats or fungus gnats?

The insects look like outdoor gnats. They were small enough to gain entrance and they can be attracted to the light and are trying to get out. Gnats like to breed in wet areas. It is possible you may have issues until the weather breaks.
mh

Attached is a better shot of the gnats that have infested our home.
Are they outdoor gnats, fungus gnats or something else?

There are hundreds of different species of gnats. We can't tell you exactly which one this is. All of them breed in wet places.
Absent some area of wetness in your home, saucers of water under overwatered houseplants (could put a bag over it for a day or two and check),
wet washcloths, leaking under a sink etc., they would be making entry from outdoors.

Do you live near bodies of water? Swampy, marshy areas?

There are certainly bumper crops of many insects from the heavy and repeated rains over much of Maryland this year.
Again. They are a nuisance, but they are harmless.

cm