How to Get Rid of Gnats

Find out what causes gnats, how to get rid of them and how to make sure the gnats don't return using a variety of human-made and natural methods.

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February 03, 2020

Photo by: Lyudmila Mikhailovskaya

Lyudmila Mikhailovskaya

Gnats — small, flying insects with long legs — are worse than annoying when they show up in your home or outdoor living spaces. They can damage plants and even cause health problems.

What is a Gnat Anyway?

Not all gnats are bad. Some help pollinate plants and devour aphids, scale and other pests that damage or destroy ornamentals and food crops.

There are four tiny, flying species commonly referred to as gnats:

  • Drain flies. These tiny pests are often found in or around drains, sewers, septic tanks and areas where sewage has leaked.
  • Fruit flies. These gnats are attracted to rotting or fresh fruits and vegetables, moist organic materials and liquids like soft drinks, wine and vinegar.
  • Phorid flies. Like drain flies, phorids like to swarm around garbage, drains and rotting fruits and vegetables.
  • Fungus gnats. These are often found around overwatered houseplants when excess water causes organic matter in the soil to decay. Adult gnats are simply annoying, but their larvae can feed on plant roots, causing the plant's leaves to turn yellow and drop or the entire plant to wilt and die. Fungus gnats can also spread a pathogen that causes damping-off, a condition that kills seeds before they sprout and weakens or kills seedlings just after sprouting.
Fungus Gnats On Trap

Yellow Sticky Trap

Control tiny fungus gnats that swarm around potted plants with a sticky yellow trap.

Photo by: Julie Martens Forney

Julie Martens Forney

Control tiny fungus gnats that swarm around potted plants with a sticky yellow trap.

What to Do About Gnats

These tiny insects often swarm around the damp soil in potted plants or near bruised or over-ripe fruit in your kitchen. You may also spot them around your sink, where they're drawn to decomposing food in the garbage disposal, or outdoors around light fixtures on porches and patios.

Bacillus thuringiensis

Fungus Gnat Control

Use a product with Bti, Bacillus thuringiensis israelensis, to kill fungus gnat larvae.

Photo by: Julie Martens Forney

Julie Martens Forney

Use a product with Bti, Bacillus thuringiensis israelensis, to kill fungus gnat larvae.

Fortunately, gnats won't damage your house, but some present a health risk. While all gnats can bite, not all species have mouth parts that can penetrate the skin. However, those that can pierce your skin may transmit pathogens and diseases, and their bites can cause itching redness, irritation and swelling. You may need to see a doctor if these symptoms occur.

How to Get Rid of Gnats in the House

Gnats reproduce in cycles and their populations can increase quickly, so you may need to use more than one method to get rid of them completely. Try these natural controls before you reach for pesticides or insecticides:

1. Gnat Trap

Gnats are drawn to the color yellow and can be trapped on special yellow cards covered with a sticky adhesive. For best results, use small cards or cut larger ones into small squares. Lay them on the soil in your potted plants or attach them to twigs or skewers stuck into the pots. Once the traps are full, discard them in an outside trash can.

2. Food-Grade Diatomaceous Earth

DE, as it's known, is an organic, abrasive powder you can buy to sprinkle over the dry soil in your plants. It will trap the gnats until they die from dehydration. Don't apply it when the soil is wet, or it won't work. To make sure the DE stays dry, you may want to put a layer of sand on top of your potting soil and then apply it, and water your plants from the bottom while using it.

3. Flypaper Ribbons

These sticky ribbons will catch gnats, but place them carefully around your house. They'll grab onto almost anything, including your curtains, hair and furniture. Don't use them outdoors, where they'll trap beneficial creatures.

4. One-Part Water to One-Part Apple Cider Vinegar

Fill a shallow saucer with this solution and mix in a few drops of liquid dishwashing soap. Keep it near your affected plants. The gnats will fall into the liquid and the soap will keep them from escaping. Add fresh vinegar and water as needed until the gnats are gone.

5. Drench the Soil in Potted Plants

Bacillus thuringiensis (Bt) is a bacterium that occurs naturally in the soil. Bt var. israelensis (Bti) kills the larvae of fungus gnats. Follow the directions on your product to make a Bti drench and use it to saturate the soil in your potted plants. It will coat the plant roots without harming them and kill fungus gnat larvae that try to feed on them. You can find Bti formulated for houseplants and outdoor plants.

Once the gnats are gone, let your houseplants or outdoor plants dry out slightly between waterings to discourage the adults from returning and laying more eggs. If you see gnats around the drainage holes of your pots, put small pieces of fabric over the holes — but make sure excess water can still drain out.

Also, remember to refrigerate fruits and vegetables, when possible, and throw away decaying or bruised foods in outdoor trash containers.

How to Get Rid of Gnats Outdoors

As an alternative to saturating outdoor plants with a Bti drench, you can drop a mosquito dunk labeled as safe for use around pets and wildlife in a watering can or bucket. Let it sit overnight or long enough for the dunk to soften and release its insect-killing bacteria into the water. Then remove the dunk, save it for later use and pour the water over the soil in your outdoor plants. Do this for several weeks to ensure any gnat larvae in the soil are killed.

Electric pest traps aren’t recommended for gnats, because they often kill beneficial insects along with real pests. Traps that use ultraviolet lights to attract gnats can work, but they only trap the adults, so any larvae that remain can grow into adults and reproduce, starting the cycle over again.

Some gnats like to swarm around porch lights or other outdoor lights and sneak inside to fly around your TV or lamps. To discourage them, switch to yellow "bug lights" or low voltage bulbs, or keep lights near doors and windows turned off. Some pest control manufacturers add a pheromone that attracts gnats to their light traps and report this can help when used as part of a larger gnat management effort.

If you get bitten but can't see what's biting you, you may have encountered tiny, biting midges, also called sand gnats and no-see-ums. Avoid their bites by staying indoors on damp, overcast days when the air is still, or cover up as much as possible when you're outside. Insect repellants and insect repellant clothing may also help.

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