Gnats are tiny flying insects that buzz around and are very annoying. They thrive on anything that's decaying, such as rotten fruit. Every gnat can lay about 200 eggs at a time, so any fruit that's left lying around will have gnats on them in no time at all. Over-watered houseplants and wet compost also attract gnats. The gnats' larvae is what will kill your house plants. The larvae damage the root systems of infested plants by digging into the soil and feeding on the roots. Seedling plants can be severely damaged by gnat larvae. You can prevent attracting gnats to your plants by not to over watering your plants [source: Wallace]. If you're convinced you have gnats in your house, here's how to get rid of them.

  • Let the soil of your houseplants dry out by not watering them for a while. Gnats need water to survive, so if you starve them of water they will disappear. When you see the plants are beginning to dry out, water them a little. This way, you will be denying the gnats their favorite home.
  • Use an organic insecticide called bacillus thuringiensis (Bt/H-14), which is a very effective in gnat control, yet harmless to your plants. Bacillus thuringiensis is sold commercially as Knock Out Gnats. Simply mix 2 to 8 teaspoons (depending how severe you problem is and how many plants you have) per gallon (3.8 liters) of water and drench the houseplant's soil with it. The insecticide will be absorbed into the soil, and when the gnats ingest it, they'll die [source: Weekend Gardener].