Hydrogen Peroxide to control Fungus Gnats - Ask Extension
Several people in my online gardening group are suggesting Hydrogen Peroxide to control Fungus Gnats. Water the infected plants with 1 part HP and 3 p...
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Hydrogen Peroxide to control Fungus Gnats #737733
Asked March 05, 2021, 4:57 PM EST
Several people in my online gardening group are suggesting Hydrogen Peroxide to control Fungus Gnats. Water the infected plants with 1 part HP and 3 parts water. Is this a safe option? Can it also be used on seedlings?
Ramsey County Minnesota
Expert Response
While hydrogen peroxide may be effective for fungus gnats, there are other, less severe, controls you should try first. These include cleaning out breeding places, using fresh potting soil and bleach-cleaned pots and containers, and, perhaps, Bt. Also consider that fungus gnats are harmless and only annoying. Look here:
https://extension.umd.edu/hgic/topics/fungus-gnats-indoor-plants
https://extension.umd.edu/hgic/topics/fungus-gnats-indoor-plants
Hydrogen peroxide is a strong oxidizing agent and will kill a lot of organisms. In fact, it is used as a sanitizing agent (although bleach is cheaper). So if you use it, do so cautiously. I would not use it on seedlings. Seedlings should be planted in fresh soil-less potting mix in clean containers, so fungus gnats should not be an issue.
The formula for hydrogen peroxide is one part 3% hydrogen peroxide solution to four parts water.
