How to Kill Gnats Without Harming Plants
- 1). Allow the soil to dry completely between irrigations. This will starve the larvae of moisture and kill them.
- 2). Control the adult gnat by spraying it with an insecticide containing pyrthrins or pyrethroids, per label instructions. Take the plant outdoors to spray it and bring it back indoors after the insecticide dries. Repeat the application every two days for two weeks.
- 3). Kill gnat larvae with a biological insecticide Bacillus thuringiensis subspecies israelensis (Bti). This is generally sold as a soil drench. Apply it per package instructions. Repeat the treatment every week until all the larvae is killed.
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