What Are Fungus Gnats?

Fungus gnats are small flying insects that swarm around houseplants in potted environments. While they are usually nuisances, high populations can pose significant problems in greenhouses, nurseries and interior plantscapes.

To reduce breeding, ensure soil is well-drained and avoid overwatering; additionally, clear away debris and compost piles where fungus gnat larvae could develop; consider using predatory nematodes like Steinernema feltiae or Bacillus thuringiensis var. israelensis to control pests.


Adult fungus gnats can become a nuisance when their numbers reach alarming levels both indoors and out. Resembling mosquitos but without bites, adult fungus gnats feed on organic matter that rots while damaging plants by flying into them; especially seedlings and cuttings which they may come into contact with while flying about the greenhouse or sod farm. Furthermore, these pests may spread diseases among their fellow plants which they feed upon as they feed off of decayed matter in greenhouses and sod farms where these insects feed on decayed organic matter while feeding on decayed organic matter that feed off of rotting organic matter while feeding upon it before invasion of greenhouses and sod farms where plant diseases spread rapidly throughout their populations causing problems to both plant species by eating it from being fed upon as it decays; this means adults do not bite and instead feed off of decayed organic matter that grows decayed organic matter that they feed off. These pests feed on decayed organic material while flying into plants which damage seedlings, cuttings, etc. Fungus Gnats also spread diseases among greenhouse and sod farms plants by flying directly or by flying into them as adults feed off both species by flying directly hitting seedlings etc thereby spreading. Fungus Gnats spread plant diseases as greenhouse and sod farms respectively a great threat fungus Gnats spread them!

Fungus gnats belong to the Sciaridae family of flies and are part of an ecosystem, though in larger numbers they can become harmful. While not harmful alone, their breeding can contaminate soil and growing media and potentially damage vegetables, fruit and flowers crops; plus they carry disease-causing fungal pathogens which may infected with fungal pathogens that cause infection.

Cockroaches can often be found indoors in greenhouses, sod farms, houseplants or gardens; while outdoors they often prefer moist growing medium such as garden beds or container mixes made from materials such as peat moss or coco coir.

Adult females typically live for 7 to 10 days before laying 30 to 200 whitish-yellow eggs singly or in clusters in crevices and cracks on the surface of growing media, particularly moist, rich soils. After hatching, larvae tend to remain within 2-3 inches of soil where there may be fungi, algae or decaying organic material present; feeding on its contents as well as any plant roots or leaves resting upon it.

Once larvae consume sufficient fungi and organic materials, they form a thread-like cyst which breaks open to reveal a pupal stage resembling banana peel in color and transparency. Adults then emerge within days.

Fungus gnats can be persistent pests of houseplants. Their weak flight means they often gather around infested houseplants near windows; this problem becomes particularly evident during late autumn and winter when more houseplants come indoors.

Biological and chemical measures can both help reduce populations of fungus gnats. Nematodes containing Steinernema feltiae can be particularly effective at eliminating adult gnats by feeding on them and secreting bacteria to kill them; mail-order solutions like these must typically be applied judiciously; insecticide sprays with pyrethrins, permethrin, or bifenthrin can also be applied at short intervals to achieve good results.


Fungus gnat larvae feed on organic matter and, sometimes, plant roots, creating problems in greenhouses, nurseries and potted plants where they may harm delicate seedlings or young houseplants by munching away at their roots. They can also spread harmful fungi such as Pythium that causes seedlings to rot and eventually kills off their host plants.

Larvae are tiny black worm-like flies that typically reach around an eighth of an inch long. Their flattened bodies and long legs give them the appearance of mosquitoes, giving the larvae their common name.

After two weeks of development, gnat larvae pupate near the soil surface in thread chambers near its surface, lasting three to seven days as pupae before emerging as adult flies and emerging back onto the soil surface; their entire life cycle takes around 17 days at typical room temperatures.

Adult flies are common nuisance pests in greenhouse and indoor plant growing areas, but are unlikely to do much lasting damage to plants. Most damage occurs from feeding on roots and interfering with their ability to uptake water and nutrients for absorption by plants.

Gnat larvae tend to cause more damage than adult gnats, although they do not bite or transmit disease. Gnat larvae can become particularly problematic in greenhouses, nurseries and sod farms where they feed upon young seedlings or less established greenhouse plants with shallow roots; less commonly seen among potted plants.

Larvae can be controlled using various commercially available and natural biological control agents; however, physical and cultural management tactics that reduce moisture in growing medium and soil tend to work better in controlling larvae infestation.

Microbial insecticides such as Bacillus thuringiensis subsp. israelensis (Bti) and imidacloprid can also be effective against fungus gnats in greenhouse and interior plant environments, either alone or combined with pyrethroid insecticides in formulations such as granules and slow-release spikes to control them in growing medium. They should not be used on outdoor or garden plants, however.


Fungus gnats may not cause immediate damage to houseplants like other pests may, and do not bite. But their numbers can quickly get out of hand and result in plant wilting, stunted growth and yellowing as their larvae feed on fungi, organic material in soil and sometimes chew through plant roots – especially serious in greenhouses, nurseries and sod farms where seedlings, cuttings or young plants with thin roots may be vulnerable to harm from these larvae feeding on them – while spreading various plant fungal diseases such as black Root Rot, Pythium Blight and Verticillium Wilt.

Serious infestation symptoms typically include generalized wilting or loss of vigor in plants, along with small spots of yellowing in their foliage. Gnat infestation is most often identified when large numbers of them begin buzzing around potted plants or near lights in an indoor garden.

Gnats are pests found indoors that thrive in damp soil. When potted houseplants have damp soil where gnat eggs can be laid, and moist potting mix or container media, these insects become a constant nuisance in homes and offices with potted plants. One effective way to combat gnat infestation is through regular drain cleaning in sinks and toilets to decrease the presence of these pesky insects in household environments.

Fungus gnat life cycles take only days to complete in warm indoor temperatures and often have multiple generations occurring simultaneously. Eggs hatch within four to six days and larvae quickly develop; when their preferred sources of food run out, larvae start eating plant roots, leading to stunted plant growth or even wilting and death of entire crops.

Adult gnats are small dark gray or black insects with long legs and transparent wings featuring a distinct Y-shaped vein in the center, similar to fruit flies or mosquitoes in appearance, making it difficult to detect. Like their outdoor counterparts, indoor gnats tend to fly short erratic patterns near screens of electronic devices or sunny windows and congregate near houseplants or glowing screens of electronic devices – weak flyers which tend to gather together.


Fungus gnats typically do not cause serious damage to plants outdoors or greenhouses. Indoors, they may become an inconvenience in houseplants and potted plants grown in soil, potting mix or containers with high organic matter content such as soil. They’re also commonly encountered as pests in commercial flower, nursery and greenhouse operations where their larvae feed on plant roots to cause seedling rot.

Adult mosquitolike flies with long legs and one pair of clear wings, weak fliers that often hover near houseplants near the tops, these moisture-attracted pests may become more abundant during wetter weather than usual. Females lay small eggs on organic debris like leaf mold, mulch, compost, grass clippings and soil; larvae develop rapidly under warm conditions producing multiple generations per year.

Fungus gnat larvae feed on organic material found in soil, such as fungi or roots. Though typically harmless to most plants, greenhouses or sod farms may face greater problems from fungus gnats due to them nibbling at roots or damaging roots directly.

To combat fungus gnats in potted plants, allow the soil surface to dry between watering sessions and use an insecticide spray specifically labeled to be effective against flying insects like gnats and mosquitoes. Houseplants with infestation can be placed into quarantine for two weeks after receiving insecticide applications containing bifenthrin, cyfluthrin, permethrin or lambdacyhalothrin may provide short-lived but effective controls; more frequent applications may be needed over time for complete coverage.

Containers should be free from excess soil, with drainage holes for drainage purposes and smaller pots to help reduce gnat attraction. You could also place sticky cards inside greenhouses and garden centers to catch any that land. Targeting larvae and eggs or those with long-lasting activity (such as Azadirachtin, Carbaryl Malathion or Pyrethrins) with specific insecticides will more effectively decrease pest numbers than short-acting contact insecticides. To gain more information on controlling fungus gnats in greenhouses, nurseries or other commercial operations, refer to the University of California Integrated Pest Management Guidelines: Floriculture and Ornamental Nurseries as well as S.H. Dreistadt’s book entitled “Integrated Pest Management for Greenhouses and Nurseries by UC Cooperative Extension”.

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