Answer: What you describe sounds like fungus gnats. Fungus gnats feed and breed in decaying organic matter so the potting soil used for houseplants provides an almost perfect environment for them. They are opportunists and tend to fly in when doors and windows are open. There's really nothing you can spray to keep them from entering your home, but you can eliminate their breeding and feeding sites indoors to keep the population under control. One of the easiest ways to control them is to place a barrier between moist potting soil and the little pests. You can simply cover the soil with aluminum foil or plastic wrap, or cover the top of the soil with pea gravel or decorative rock such as those used in aquariums. Whatever you use, make sure there are no tiny entrance holes for the gnats - they're sure to find them. To capture any that are just flying around you can prop yellow sticky traps at foliage level. For some reason the color yellow attracts them and if you smear a piece of bright yellow construction paper or poster board with petroleum jelly the gnats will land on it and get stuck. Replace the sticky traps every few weeks and eventually you'll reduce the population of gnats in and around your houseplants. Both of these solutions are child and pet-friendly and both work for me and my houseplant collection. Or, a chemical solution might be to drench the soil with a product called Gnatrol. Best wishes with your houseplants!
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