The Q&A Archives: How can I get rid of fungus gnats?

Question: I believe I have fungus gnats in some of my houseplants. I'm not sure what else to do to get rid of these pests. When I water I see small white wormlike bugs crawling in the soil. I have tried letting the soil dry out but when I do water again, they come back. I have tried changing the soil and even baking the soil. I have a lot of house plants and do not want to throw any of them away.They don't seem to be hurting the plants but are annoying to me. Any suggestions on how to rid my plants of these pests once and for all. Also they do not seem to like my africian violets and only infest certain types of my plants.

Answer: Usually they feed on organic matter in the soil but they can start in on the roots as well, so you probably do want to control them. Typicaly they breed in damp soil so overwatered plants or plants that like a wetter soil will be prime candidates although I have seen them on many diffeent plants and suspect it is related to what was used in the potting mix ingredients, too. Control is not too difficult. One method is to put a layer of sand on top of the potting mix in each pot. The sand will dry out almost immediately after each watering, and since they don't breed in dry soil, you will interrupt the breeding cycle. Another option would be to use a soil drench such as Gnatrol, an insecticidal soap product. Your local garden center should be able to show you similar products if Gnatrol is not available in Canada. I hope this helps!

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