Tiny white bugs on potting soils

Written by tracy hodge | 13/05/2017
Tiny white bugs on potting soils
Fungus gnats live in the potting soil of houseplants. (orchid houseplant closeup image by Matt Batchelor from Fotolia.com)

Indoor plants provide warmth to any home or office. All indoor plants require care and maintenance to remain healthy and vigorous. Insect infestations can compromise the health of your indoor plant and become a nuisance. Fungus gnat larvae are tiny white wormlike pests that are often found on potting soil of indoor plants. Once the larvae becomes an adult fungus gnat, indoor swarming is often a problem for the homeowner.


Adult fungus gnats are also known as dark-winged fungus gnats and are approximately 1/8 inches in length, have wings and long legs. Fungus gnats look similar to miniature mosquitoes, but they do not bite humans. Fungus gnat larvae are grey or white worms that measure approximately 1/4 inches in length. Fungus gnats live deep in the potting soil and are difficult to see. Larvae often rise to the surface of wet potting soil in the early morning hours.


Fungus gnats are nuisance insects that live in the potting soil of indoor plants. Homeowners may detect these pests when they move their plant, as this may cause fungus gnats to swarm. Fungus gnats are the most problematic during the fall and winter months, because homeowners often do not reduce the amount of water provided to their indoor plants. Indoor plants do not require as much water during periods of cooler weather and moist potting soil attracts fungus gnats. As potting soil ages and degrades, it retains even more moisture which is attractive to fungus gnats. Fungus gnats do not feed on indoor plants, but drink the water from plant leaves.

Cultural Controls

Reducing the amount of water provided to your indoor plant during the cooler fall and winter months will help prevent fungus gnat infestations. Once potting soil begins to break down and retain excessive amounts of moisture, you should repot your plant. Yellow sticky traps will often trap adult fungus gnats and are most effective if placed directly above the plant. Heavy infestations of fungus gnats often require chemical control methods.

Chemical Control

Pesticides are effective in fungus gnat control when applied as a soil drench. Apply these products directly to the soil and follow all label instructions for use. Pesticide sprays are available for fungus gnat control and are applied to foliage and soil surfaces of indoor plants.

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