To eliminate fungus gnats, stop watering houseplants to allow the soil to dry out, and apply a biological agent or commercial insecticide to the soil. Use yellow sticky traps to capture adult gnats, and move damp materials outdoors to reduce gnats on the property.Continue Reading
Overwatering is a common cause of gnat infestations in houseplants. Stop watering the affected plants to allow the soil to dry out, and transplant the plants into a self-draining container if needed.
To kill gnat larvae, apply a biological agent, such as Bacillus thuringiensis var israelensis, to the soil, or apply a pyrethrin-based pesticide to the soil according to the directions on the product packaging. Choose an insecticide that is labeled for indoor use when treating houseplants. Frequent applications of the insecticide eliminates adult gnats. To hasten the process of removing adult gnats, place yellow sticky traps on the soil surface of the affected houseplants.
To prevent fungus gnats from returning, remove damp mulch and other organic matter near the home, and repair water leaks that may attract the pests to the property. Install screens on windows, and seal windows and doors to prevent gnats from entering the home.