How to Get Rid of a Gnat Infestation
Gnats are nuisances, prone to hover around warm bodies and fermenting foods. If you felt like a gnat was targeting you while you sipped on a glass of wine, well, you were right. Humans, pets, and areas in your kitchen can be a magnet for these annoying pests. Controlling a gnat infestation starts with disrupting their life cycle, and the first step to doing that requires learning more about these common household guests.
What's a Fungal Gnat?
A gnat is a small flying insect belonging to the order Diptera, which includes fruit flies and mosquitoes. Fungus gnats are a specific type of gnat that belong to the family Sciaridae. Unlike fruit flies, they primarily infest soil containing organic material, particularly in potted plants. Adult fungus gnats lay their eggs in moist soil. During the larval stage, the fungus gnat larvae feed on fungi, algae, and plant roots. This makes them particularly problematic for indoor plants, as they can can contribute to root rot and degrade the quality of plant soil. Fungus gnats are often recognizable by their small size, slender, oval-shaped bodies, and long legs.
What Causes Houseplants to Breed Gnats
Overwatering. Wet soil attracts adult gnats, which thrive in damp conditions. Excess water in a potted plant is the perfect breeding ground.
Organic matter. Decomposing organic matter in the soil provides a breeding ground for gnats.
Poor drainage. Inadequate drainage holes prevent water from escaping, leading to waterlogged soil ideal for gnat larvae.
Potting mix. Some commercial potting mixes may contain organic matter conducive to gnat infestation.
Infected plants. Bringing in new plants without proper inspection can introduce gnats and other pests into the environment. So, yes, that goes to say that if one of your houseplant has a fungus gnat infestation, others may too.
Lack of air circulation. Stagnant air around houseplants can exacerbate moisture buildup, encouraging gnat breeding.
Related: How to Choose the Best Soil Mixes For Potted Plants
6 Ways to Get Rid of Houseplant Gnats
1. Reduce Soil Moisture
Make sure your planters have proper drainage.
Avoid overwatering to eliminate the moist environment that attracts gnats. The best way to do this is to make sure the top few inches of soil are dry before you apply more water to the soil surface. If you normally water twice a week, reduce it to once a week. That small change can make a difference.
Additionally, when you do water, use a hydrogen peroxide solution to "disinfect" your soil. A 1:4 mixture of hydrogen peroxide and water will safely kill the larvae without killing the roots of plants.
2. Turn on a Fan
Improving the air circulation around your plants can reduce fungus gnat issues. Running a fan nearby or opening a window during the summer can make the houseplant less hospitable.
3. Create a Jar Trap for Adult Gnats
Controlling the pest population starts with baiting adult gnats. While they're drawn to wet, organic decomposition in your potting soil, they're also keen to sample fermenting liquids, which is why wine and apple cider vinegar traps are so effective. They also really like rotting fruit, which can serve as a great lure into the trap you build.
Pour two tablespoons of your chosen liquid into a small jar. Add a few drops of dish soap to disrupt surface tension and prevent escape.
Sweeten the deal by putting a piece of rotting fruit into the jar. This could be a slice of orange, a softening cherry tomato, or a few overripened grapes.
Cover the jar trap with plastic wrap or tape. Rather than making small cuts for them to access, I prefer to leave one edge of the cup uncovered. The tape acts like a sticky trap for when they get confused inside the container.
Place the gnat trap nearby or directly on the soil of your affected houseplant.
I like the jar trap option as a first try; if it doesn't work for the extent of your infestation, upgrade to sticky traps. The color yellow is a draw for gnats, so yellow traps draw the pests in, and the sticky adhesive strip traps them on contact.
4. Use a Potato Trap for Gnat Larvae
A raw potato can serve as a gnat larvae trap. It won't eliminate the infestation, but it can help!
Cut a potato. Slice a raw potato into thin slices or wedges.
Place in soil. Insert the potato pieces into the soil of infested houseplants, ensuring they are partially buried.
Wait and monitor. Leave the potato slices in the soil for a day or two. Fungus gnat larvae are attracted to the potato, and they will crawl into it to feed.
Remove and dispose. After a day or two, carefully remove the potato slices from the soil. You may notice larvae on the potato pieces. Dispose of the potato and larvae to reduce the gnat population.
5. Replace the Potting Soil
If your plant is suffering, the damp soil conditions and gnat larvae may have exacerbated root rot. Give your plant a chance to rebound by offering it fresh potting soil. Choosing the right potting soil is important, and products with natural fungicides or additives like perlite and pumice can help with drainage and root health. Repotting the plant in fresh soil can help eliminate eggs and larvae. Rinse the roots hairs of the plant so you reduce the likelihood that any larvae carry over into the new soil. Then, moisten the soil, but be mindful of oversaturating it.
6. Apply Neem Oil
Take proactive measures. If you continue to have on-again-off-again issues with gnats, try neem oil. Dilute one tablespoon of neem oil in one quart of water. Keep it handy in a spray bottle. Spray this natural remedy on the soil surface. Its compounds deter gnats and kill larvae. Apply according to instructions, and consider testing on your plant before widespread use.
Related: 13 Plants and Trees That’ll Thrive in a Bright Home
