Nuisance Gnats Indoors in the Fall?

By Chris Williams on December 4, 2015.

It’s almost winter and we have little gnats in our house. Isn’t that unusual? I don’t think they’re fruit flies but they’re tiny and annoying. They don’t seem to come from any particular place, it’s like they follow you around the house.

W. P., Rye, NH

There are a number of possibilities for these little flies or gnats. Fruit flies is one, but phorid flies, fungus gnats, or drain flies are other possibilities. All are tiny flies that breed in some kind of decaying organic material — from rotting fruits to potting soil to the scum inside drain pipes. Because the food material for the larvae can be found inside your home, it doesn’t matter to these flies what the weather is like outside. They can maintain an ongoing population without ever leaving your house as long as the food source remains.

Some of these flies can be pretty much in-your-face as you say, flitting around your nose and mouth. They’re probably attracted to body warmth and the CO2 given off when you breathe. If you’re drinking wine or beer, or eating something yeasty or vinegary, you’ll attract fruit flies since they detect odors of fermentation. Some tiny flies are also attracted to lights.

Where Are the Annoying Gnats Coming From?

These are the main breeding sites for each of these little flies, although there can be overlap since each breeds in a range of sites.

  • Phorid flies – Larvae can feed in the scum inside dirty drains, or in moist decaying materials in various sites such as in drip pans, garbage cans, produce bins, garbage disposals, overwatered plants, or in sewer line breaks. See Phorid Flies Have Terrible Dining Habits!
  • Fungus gnats – Larvae feed on decaying plant material in the soil of overwatered houseplants, or in other sites where mold is growing. See Finding Fungus Gnat Breeding Sites.

This is one situation where you really do need the help of a professional exterminator who can identify the flies and conduct a thorough inspection to find the breeding source or sources. Give Colonial Pest a call today.



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