tiny, fllying gnats in houseplants soil

Asked June 26, 2017, 8:46 AM EDT

Help please. I continue to have tiny, flying gnats in my houseplants' soil. These gnats resemble a fruit fly. They occasionally are seen flying in the house, but are concentrated in my plants' soil. They are visible in the soil and around the pots. I have tried the following remedies, with no avail, to rid my plants of these pests: I have removed all potting soil, washed the plants' roots, and replaced the soil with high quality potting soil. I have tried covering the soil with newspapers to prevent bugs from multiplying. In addition, I have placed yellow sticky tape and fruit fly traps in the plants. I have also put the plants outside for a period of time. As a last resort I discarded all my houseplants and replaced them with new, only to have the gnats eventually return. I would appreciate any suggestions you may have. Thank you.

Iowa County Iowa

2 Responses

Hello:

Thank you for your message and for contacting Iowa State University. Problems with fungus gnats in houseplants are common. The gnats are annoying but not harmful to the plants or to house contents or people. The first recommendation is to allow houseplants to dry out between waterings. There are insecticides available to greenhouse growers but these are of limited availability to homeowners.

http://extension.colostate.edu/topic-areas/insects/fungus-gnats-as-houseplant-and-indoor-pests-5-584...

Hydrogen peroxide is a common disinfectant and mild fungicide used in greenhouse sanitation. I have no evidence it will eliminate fungus gnats in the soil as claimed on the Internet.

Thanks.

Donald Lewis

Thank you for your quick response. It was very helpful.