What Can I Spray on My Potted Plants to Kill Gnats or Little Flying Bugs?

Adult Gnats

• Eliminate nuisance adults with any insecticide spray or aerosol labeled as effective against gnats or flying insects. Sprays based on pyrethrins are effective against adults although they do not kill the larva. Alternatively, spray adults with a product based on insecticidal soap or horticultural oil. Contact insecticides work only if combined with larval control methods, such as reducing the frequency of watering and removing soil debris.

Persistent Insecticides

• For longer-lasting relief, spray your plants and the surrounding area with a persistent insecticide containing bifenthrin, cyfluthrin, permethrin and lambda-cyhalothrin to control adult gnats for at least three days. These last longer than pyrethrin-based sprays but still do not eliminate the larva in the soil.

The Larva

• Use a product containing imidacloprid to treat fungus gnat larva. It is available for household use as a spray in combination with pyrethroids as well as a soil drench or in slow release formulations.

Alternatives

• Ask in your garden center for biological control solutions for fungus gnats. These include parasitic nematodes such as Steinernema feltiae, the bacteria Bacillus thuringiensis var. israelensis and parasitic wasps.

Whitefly

• Whiteflies are smaller than fungus gnats at only 1/16 inch and resemble white moths. They feed on the sap of host plants using piercing mouthparts while their larva live on leaf undersides. Treat whitefly with insecticidal sprays based on insecticidal soap, horticultural oils pyrethrins or permethrin. Spray your plant every week for five weeks to completely eliminate whitefly.