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Fungus Gnat Control: Rubbing Alcohol Dilution and Soil Fixes

Follow-up to a previous query: reader asks for rubbing alcohol-to-water ratio for fungus gnats, noting they have cats and avoid pesticides. They summer plants on a balcony (Canada), brought them in, and have gnats despite Safer's soap.

Alcohol Treatment

Use at least 2 parts rubbing alcohol to 1 part water, or straight rubbing alcohol (already diluted ~70%). Straight alcohol evaporates fast, not worsening wet soil. This is only a temporary fix.

Permanent Solution

Dry out plants more between waterings. Gnats thrive in constantly moist soil.
Repot with amended mix: 2 parts potting soil + 1 part perlite + ¼ part horticultural charcoal. Increases porosity and aeration, preventing root rot that attracts gnats.

Overwatering kills more plants than underwatering. Address the moisture root cause for lasting control.

House Plants: Fungus Gnat Management: Soil Moisture, Barriers, and Biological Controls; Marketing High-Quality Black Soil and Peat Deposits in Minnesota; Black Flies and Wasps on Tree: Aphid Honeydew Attracts Them—Control the Aphids; Eliminating Fungus Gnats from Wandering Jew Plants; Eliminating Fungus Gnats Without Repotting 25 Plants; Fungus Gnats on Jasmine & Angel Wing: Repotting Shock + Overwatering; Fungus Gnats on Cacti and Succulents: Dry Out the Soil; Eliminating Fungus Gnats After Repotting; Fungus Gnats on Dieffenbachia: Causes and Cures; Fungus Gnat/ Fly Infestation from Unfinished Compost

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