How to Get Rid of Gnat Larvae With a Potato

Fungus gnats are not true gnats. They are tiny flies, 1/8 inch or less in length, often seen hopping about on the surface of houseplant soil or congregating in a warm, sunny window. The adult flies are harmless, though annoying. The females lay up to 300 eggs at a time on moist potting soil. The larvae that hatch from the eggs feed on decaying organic matter in the soil and tender young plant roots. Potato slices are useful for detecting fungus gnat larvae, but to get rid of the gnats you must reduce the amount of water the plant receives. Fungus gnat larvae live in the top 2 to 3 inches of potting soil, and when that portion of the soil dries out, the larvae die.

Things You'll Need

• Sharp knife

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Instructions

1. • 1

     Cut a potato into 1/4-inch slices that are at least 1 inch in diameter.

   • 2

     Put the potato slices on the surface of the potting soil and press so that there is good contact between the soil and the potato.

   • 3

     Check for fungus gnat larvae on the underside of the potato and the soil beneath after two days. Look for tiny, whitish, threadlike larvae with black heads. Discard potato slices infested with larvae and replace them with fresh slices.

   • 4

     Water the plant only when the top 2 to 3 inches of soil is dry until you no longer find fungus gnat larvae on the potato slices.