How to Kill Fungus Gnats With Household Items

Let all indoor potted plants dry out completely before watering them again. Brief periods of drought shouldn’t harm the plants, but should kill any fungus gnat larvae in the soil. To check the moisture level, push a stick several inches into the soil and examine it. When the soil is completely dry, either water the plant or leave it for another day or so if it belongs to a hardy species. Some plants, for example succulents and cacti, can be left for weeks without water, which will almost certainly eradicate the fungus gnat population.

Squirt a little liquid dish soap into a plant mister, add water and stir. Replace the top and saturate the soil of your houseplants with the mixture. Spray any visible gnats directly. Dish soap is toxic to both adult fungus gnats and their larvae, but harmless to plants, people and pets.

Fill yellow cups, bowls or other containers with water and place them near your plants and anywhere else that fungus gnats are a nuisance. These gnats are attracted to the color yellow and drown easily. Empty the cups outside once a day and add fresh water. A drop of a sugary cordial in the water might attract more gnats, and will certainly attract fruit flies if they are also a problem.

Cut slices of raw potato and push them into the soil around your plants. Remove after two or three days, when they should contain a number of gnat larvae. Put the slices into the trash or on your compost heap -- fungus gnats are rarely a problem outside, even if the larvae survive.