P:
I grew several plants outside this last summer Rosemary, Geranium, etc. When I brought them in for winter it seems I now have fungus gnats in all my houseplants. Please give advice. I would prefer not to use chemicals but am getting desperate.
R:
Winter is a time that a lot of indoor plants become infested with fungus gnats, due to excessive soil moisture.
How to control fungus gnats
- Avoid over-watering houseplants. I suggest that you check the soil before watering to make sure the top inch is dry. The larvae of the fungus gnats live in the top half inch or so of moist soil, so letting the planting medium dry out lessens the chance of infestation.
- Use yellow sticky traps. This is not a biological control, but it will reduce the population of adult gnats.
- Use Bacillus Thurengiensis Israeli (BTI). Use BTI as a drench to kill the larvae.
For additional information, check out this article for more alternatives: Fungus Gnats, University of California IPM
Want to learn more about this topic? Explore more resources from OSU Extension:
Healthy homes, Insects
