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Fungus Gnats


Fungus Gnats

by cms-admin. All rights reserved

Fungus Gnats are a large family belonging to the order Diptera. There are roughly 3000 species in total which are difficult to tell apart with the naked eye because of their small size. They're long-legged flies with slender black bodies. They thrive in damp conditions and are attracted to wet soil. Overwatering plants is the most common cause of Fungus Gnat infestations in the household. The larvae feed on fungi and decaying plant matter in the soil. Damage is never severe, but smaller seedlings and plants grown indoors are most susceptible to infestations. They can be seen active around houseplants, either flying slowly around foliage or scattered across soil at the plants base. These insects can be active all year round indoors.
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Fungus gnat infestations can be annoying and unpleasant.
Severe damage to plants is rare.


Adults: They are tiny flies with black bodies and slender black legs. The thorax is domed, giving them little hunched backs. Larvae: Tiny and almost translucent white grubs/ maggots with black heads.


Fungus gnats multiply quickly. Small, black flies seen crawling over soil of houseplants. Sudden wilting or browning of seedlings. Young plants can die.










Biological treatment

Yellow sticky traps are sold commercially online or in shops. These are not just great for catching flies but will help you assess the severity of the infestation. Leaving sticky traps on the surface of the soil will catch the eggs laid by adult flies. Sciarid fly enjoys a moist environment to live. Ensure not to over water container plants. When experiencing an infestation, it's best to water plants by placing in a saucer of water, letting the roots absorb water from the bottom up. This makes the soil surface dry and unattractive to fungus gnats. Watering plants too often with unsufficient drainage may result in rotting and fungus gnats will thrive in these conditions. Try to avoid overwatering and check soil dampness before every water. Use specific house plant compost to help reduce the risk of infestation. Incorporating perlite or gravel into the soil mixture will help better drainage if your plants are overwatered. Beneficial nematodes can be added to the soil of house plants. Hypoaspis miles is the biological control mite, for the larva of Sciarid fly is available to purchase online. By mixing peppermint, cinnamon and sesame oils and diluting with water, you can make a quick and easy non-toxic spray that will deter flying insects in the house. Alternatively, you can use a dishwashing soap and water mixture to kill larvae on the soil.

Chemical treatment

We recommend trying biological treatments before using insecticides because generally, chemical treatments are ineffective on the pupae and larvae in the soil. Chemical treatments may work in the short term but probably won't not long term. Organic pyrethroid insecticides should have a sufficient potency for indoor use. They usually contain some form of pyrethrum or natural oil. It coats the plants and sticks to any insects which come into contact with it. These sprays are much more environmentally benign, as opposed to synthetic compounds. Please take care when applying and read all available instructions. If you ever feel unsure, consult with your local garden centre or ask the wonderful Candide community!


Fungus gnats are attracted to damp, cool areas. Overwatered houseplants are most prone to infestations.
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