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Fungus gnats are manageable, but you usually need to deal with both the flying adults and the larvae in the soil. Sticky traps only catch adults, and drying the soil only slows the larvae, which is why each step on its own rarely ends the problem. Gnats breed in moist soil, so a few weeks of steady treatment helps break the cycle.
A common approach, combining several steps:
1. Treat the soil with a BTI product (Bacillus thuringiensis israelensis, sold for example as mosquito bits or dunks). BTI targets the larvae of gnats and mosquitoes. Steep it in water as the label directs and use that water for your plants for several weeks. Follow the product label for dosing and use around pets and children.
2. Keep the yellow sticky traps up. They will not solve it alone, but they catch egg-laying adults and show you whether numbers are going down.
3. Let the top layer of soil dry out between waterings, and consider a top layer of sand or fine grit, which makes the surface less inviting for laying eggs.
4. Some growers also water with a diluted 3% hydrogen peroxide solution to kill larvae in the soil. If you try it, use a mild dilution (for example, 1 part 3% hydrogen peroxide to 4 parts water) and test it on one plant first.
To prevent a comeback: avoid overwatering, empty saucers, and keep new plants apart for a while to check for gnats before they join the others.
A common approach, combining several steps:
1. Treat the soil with a BTI product (Bacillus thuringiensis israelensis, sold for example as mosquito bits or dunks). BTI targets the larvae of gnats and mosquitoes. Steep it in water as the label directs and use that water for your plants for several weeks. Follow the product label for dosing and use around pets and children.
2. Keep the yellow sticky traps up. They will not solve it alone, but they catch egg-laying adults and show you whether numbers are going down.
3. Let the top layer of soil dry out between waterings, and consider a top layer of sand or fine grit, which makes the surface less inviting for laying eggs.
4. Some growers also water with a diluted 3% hydrogen peroxide solution to kill larvae in the soil. If you try it, use a mild dilution (for example, 1 part 3% hydrogen peroxide to 4 parts water) and test it on one plant first.
To prevent a comeback: avoid overwatering, empty saucers, and keep new plants apart for a while to check for gnats before they join the others.
Plant Care Club
Mar 15, 2026