fungus mites on house plants - Ask Extension
I'm about ready to toss every plant I own. I repotted my plants last spring, and ever since then have been plagued with fungus gnats .I've applied the...
Knowledgebase
fungus mites on house plants #924194
Asked February 03, 2026, 4:41 PM EST
I'm about ready to toss every plant I own. I repotted my plants last spring, and ever since then have been plagued with fungus gnats .I've applied the Bonide systemic 3 times, did the peroxide soak, and even took each plant our of the old soil, washed the roots and repotted in fresh spoil. I've got the sticky traps in each pot, but still have gnats - what do I need to do to get rid of them for good?
Stearns County Minnesota
Expert Response
You are doing all the suggested things to eliminate or reduce fungus gnats. They can be tricky little buggers! Two additional things you try are:
1. Let your plants dry out between watering. Put your finger 1” into the soil and only water when you feel no moisture.
2. Put a 1/2” layer of sand on top of your soil. This can help deter egg laying.
Below is a link to information on green plant insect control. As mentioned, you are doing much of what is recommended.
https://extension.umn.edu/product-and-houseplant-pests/insects-indoor-plants#fungus-gnats-1581117
1. Let your plants dry out between watering. Put your finger 1” into the soil and only water when you feel no moisture.
2. Put a 1/2” layer of sand on top of your soil. This can help deter egg laying.
Below is a link to information on green plant insect control. As mentioned, you are doing much of what is recommended.
https://extension.umn.edu/product-and-houseplant-pests/insects-indoor-plants#fungus-gnats-1581117
Thank you Amy - I'll try the sand. It's also been suggested that maybe they're in our drains? Do fungus gnats propagate in drains? If so, will boiling water kill them? Thanks again!
ML
On Wednesday, February 4, 2026 at 08:38:53 PM CST, Ask Extension wrote:
Fungus gnats infest soil versus drains. There are insects called drain or sewer flies. I have placed a link below that has information about these insects.
https://septic.umn.edu/news/sewer-flies
https://septic.umn.edu/news/sewer-flies
