Gnat Identification, Control, and Infestation Tips - New York, New Jersey, and Connecticut
Scientific Order: Diptera
Common Family: Six of the seven families within the superfamily Sciaroidea, particularly the family Sciaridae
Size: Adults of different species may be as small as 2 millimeters, or as large as ½ an inch (12.7 millimeters).
Color: Black, grey, or even dark orange-yellow with translucent grey or clear wings. The identifiable mark on most species is the Y-shaped, vein-like pattern in their wings.
Behavior and Diet
Fungus gnats are the most common species of gnat. They’re attracted to fungi such as mold, decaying matter and mushrooms, as well as sources of moisture. Female gnats lay their eggs in moist soil and the larvae feed on the root systems of plants, interfering with the plant's ability to absorb water and nutrients. Gnats are particularly notorious among orchid growers who prefer to keep their prized blossoms well-watered.
Adult fungus gnats are attracted to light and often swarm around indoor light sources. They're especially active during warm, moist autumn weather, when they can infest wet leaf piles during the day.
Reproduction and Gnat Life Cycle
Fungus gnats have short life spans and grow quickly. Their entire life cycle process can complete in 20 to 28 days depending on the temperature of the growth environment. The fungus gnat’s life cycle is broken up into four distinct stages: egg, larvae, pupa, and adult.
A single female fungus gnat can lay up to 300 eggs at a time and can lay up to 1000 eggs in her lifetime. Eggs hatch quickly. Larvae feed continuously and require considerable moisture and energy to pupate. After around 10 days, larvae pupate. After about 7 days pupating, they emerge fully grown.
Gnat Control and Signs of Gnat Infestation
Signs of a Gnat Infestation
Adult gnats are attracted to light sources, especially at night. The best way to spot a gnat infestation is to look for swarms of black gnats around indoor and outdoor lights at night, especially in warm or humid areas.
In homes gnats are attracted to fruit, garbage, moisture and houseplants. Fungus gnat larvae burrow into the soil to hide and feed more effectively. Indoors, gnats will lay eggs in potted plant soil and then rest on plants nearby. You may find larvae in the soil around areas where you see adult gnats.
Gnat Control and Prevention
Preventing fungal growth is the most important way to prevent a fungus gnat infestation. Take these steps to keep gnats out of your home:
- Control humidity in your home or building.
- Fix plumbing leaks.
- Dispose of decaying organic matter.
- Store fruit in your refrigerator.
- Take out your garbage regularly.
- Maintain your indoor plants.
If you find that gnats have infiltrated your home. Here are steps you can take to repel them:
- Commercial repellents like Gnat Nix or Go Gnats.
- Sticky traps.
- Sesame oil with cinnamon and peppermint.
- Pour diluted bleach down drains with gnats.
- Let soil dry or repot plants to kill eggs and larvae in infected house plants
Of course, getting professional help for your gnat infestation is the easiest and surest way to make sure fungus gnats don’t return.
Gnat vs Fruit Fly: What’s the Difference?
Fungus gnats and fruit flies are often confused due to their size and the level of irritation they create. Each has a distinctive look if you can get close enough to identify them. You can
also often tell by their behaviors.
- Fruit flies: like their name implies, look like a small fly. They have a round body and big eyes that are either red or dark colored. You’ll find fruit flies hovering over fruit bowls and other sweet foods or circling around your garbage can. They tend to fly solo or in small groups where there is food.
- Fungus gnats: look more like mini mosquitoes. They have long dangling legs and slimmer bodies. They are darker in color and their eyes are usually too small to notice. Gnats tend to favor hovering over potted plants and will gather in swarms. Gnats are not strong fliers and won’t be in the air for an extended time.
Biting Gnats in New York?
Fungus gnats – the most common variety - are pesky for sure, but they don’t bite. When you walk or bike through a swarm of them, you can get them in your eyes, nose and hair but they won’t bite.
Other types of gnats do bite. The females need the protein in blood to produce their eggs. The most common of these species are midges and sand flies. These gnats are likely to bite during the early morning or evening and will be found in wet swampy or wooded areas but not in the city.
Gnat bites appear as small red bumps that may itch like a mosquito bite. They are not dangerous but can become infected. People with allergies may need an anti-itch cream or antihistamine if they have a strong reaction. The best treatment is to keep the bites clean and avoid scratching them.
University of Florida Department of Entomology & Nematology darkwinged fungus gnats “Featured Creatures” page
American Orchid Society’s Orchid Pests and Diseases: Fungus Gnats page, by Paul J. Johnson, Ph. D.
University of Vermont Extension Department of Plant and Soil Science’s “Fungus Gnats” page by G.R. Nielsen
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