Learn to differentiate these minuscule menaces
Fungus gnats have slender bodies and long, dangling legs, while fruit flies are round with red eyes.
Fungus gnat larvae feed on plant roots and fungi, while fruit flies feed on decaying fruits and fermenting materials.
Fruit flies are controlled by removing food sources and using vinegar traps, while fungus gnats require soil drying and targeted treatments for larvae.
Gnats and fruit flies may be tiny, but they can be incredibly irritating. At first glance, you might not know which of these annoying insects you’re dealing with, but there are clear distinctions that differentiate them. Knowing how to identify each can help you find the most effective way to eliminate them as quickly as possible. Let’s cover the key differences between fungus gnats vs. fruit flies.
Gnats and fruit flies differ in their appearance, habitat, and feeding preferences. Gnats are slender, dark insects found in moist soil or plants or feeding on fungi, while fruit flies are slightly larger and rounder, yellowish-brown, and attracted to overripe or decaying fruit, as well as a variety of sugary substances.
| Type of Difference | Gnats | Fruit Flies |
|---|---|---|
| Size | 1.5–3 mm | 3–4 mm |
| Color | Dark gray/black | Tan/black |
| Host Preference | Plants/soil | Decaying fruit/sugar |
| Habitat | Outdoors/Indoors | Indoors |
| Disease | Do not carry disease | Do not carry disease |
Gnats and fruit flies may appear similar, but these tiny winged insects differ in size, color, and body shape. Here are the key characteristics that define them.
Gnats are smaller than fruit flies, ranging from 1½ to 3 mm, and they have a more slender body shape. Fruit flies are roughly 3 to 4 mm in size and more rounded.
Gnats are typically dark gray or black, whereas fruit flies tend to be tan or black with distinct red eyes.
Gnats have a thin frame with long, dangling legs and antennae. Fruit flies have a more compact, rounded body. Also, fungus gnats have long, narrow wings that can often appear too large for their bodies, whereas fruit flies have short, rounded wings.
Another way to easily identify the difference between fungus gnats and fruit flies is by observing their feeding preferences and where they are congregating. These are the main things to look for.
Gnats are attracted to chronically moist environments like overwatered plants, soil, or rotting organic material. They lay their eggs in damp areas and feed on fungi, hence their name. Fruit flies, on the other hand, are attracted to sugary substances, especially decaying fruit and vegetables. They feed and breed on overripe produce or food scraps left out in kitchens, and they can even hitchhike into the home via eggs laid in produce.
Do fruit flies bite? What about fungus gnats? Luckily, the answer is no to both. While these two insects can be irritating when they invade your space, you won’t have to worry about them biting.
Fungus gnats are commonly found outdoors near plants or damp soil but can also invade homes, especially around overwatered plants. Fruit flies thrive indoors, particularly in kitchens and areas where overripe fruit or vegetables are stored. If you notice swarms of small flies away from the kitchen (or anywhere human food is stored), it’s likely gnats, as they are drawn to a broader range of food sources like mold, damp soil, and houseplants.
The average lifespan of a fruit fly is around 40 to 50 days, with their life cycle consisting of four stages: egg, larva, pupa, and adult. They reproduce rapidly, with females laying up to 500 eggs in a single cycle. They transition from egg to adult in just eight days, making infestations difficult to control.
Fungus gnats have a much shorter lifespan, averaging only 14 days. Gnats lay eggs in moist soil or organic matter, and their lifecycle is completed within about four weeks.
Though fruit flies don’t bite, they can carry bacteria like salmonella, E. coli, and listeria, which can cause food poisoning. They contaminate surfaces and food, potentially leading to serious illness if it’s consumed. Fungus gnats, on the other hand, primarily harm plants. Their larvae spread fungus spores to plant roots, causing diseases such as black root rot, Pythium blight, and Fusarium wilt. While not a direct threat to human health, they can severely damage plants.
Getting rid of fruit flies involves removing their food sources, such as overripe fruit, sugary spills, or fermenting materials. Using traps made with apple cider vinegar and dish soap can lure and kill fruit flies quickly—the vinegar baits them in, while the soap breaks the surface tension and causes them to drown. Keeping food prep areas clean and sealing food items effectively will prevent further infestations.
For fungus gnats, treatment revolves around managing soil moisture, since they breed in damp environments. Allowing the soil to dry out between waterings disrupts their life cycle. Yellow sticky traps can catch adult gnats, while treating the soil with beneficial nematodes or hydrogen peroxide solutions can target larvae and prevent damage to plants.
In either case, if you’re having trouble with these pesky gnats or flies, a local bug exterminator can help you get rid of them for good with professional-grade treatments.
As fungus gnats and fruit flies have different food sources, there are different ways to help prevent future infestations.
The main way to prevent fungus gnats is to keep your home clear of things that attract gnats, such as decaying plant matter and waterlogged soil. Here’s what to keep in mind:
Avoid overwatering houseplants
Keep soil dry and well-drained
Seal cracks around windows
Fruit flies love sugary substances and overripe and decaying fruit, so it’s important to avoid leaving these around your home. Here’s what to do:
Dispose of overripe fruit promptly
Keep kitchen surfaces clean and dry
Store fruits and vegetables in the refrigerator
Inspect produce before bringing it into your home
The term “gnat” is sometimes used as a blanket term to refer to both fruit flies and fungus gnats, as well as a variety of other tiny flying insects. However, the true one true “gnat” by name is the fungus gnat. While people may mistakenly lump both insects under the term "gnat," fungus gnats and fruit flies have different diets, habitats, and characteristics from each other, as well as the other small flying insects in the “gnat” category.
Gnats may eventually go away on their own, but it depends on the source of their attraction. If the environment that’s attracting them—such as overwatered plants, moist areas, or food debris—isn't addressed, they can persist or even increase in numbers. Reducing moisture, improving drainage, and cleaning up organic matter can help eliminate them. Without these changes, gnats are likely to stick around and continue breeding, making it important to remove their breeding grounds to get rid of them for good.
If you’re wondering whether bug candles can keep flies away, the answer is yes (and this goes for fruit flies and many other types of flies. However, most bug candles contain citronella, which isn’t suitable for indoor use. This is because the fumes are strong and can leave a strong scent on walls and objects.
Bleach, which can kill drain flies, can also kill fruit flies, but it’s better to lure fruit flies to a liquid rather than applying chemicals, as it’s very difficult to reach them all. A more practical approach is to lure fruit flies with traps made from liquids like apple cider vinegar mixed with dish soap. This method is safer and more efficient, since it targets a larger number of fruit flies without relying on harsh chemicals that may not reach all the pests.
