There may be house plant gnats if you noticed a sudden rise in the number of tiny fruit flies flying or crawling around in the soil of your plants, especially after you watered them. Fungus gnats are attracted to moist soil and can breed and spread fast. The larvae feeds on organic matter and in severe cases, can feed on the roots of plants. Theyre also highly annoying.
We’ll talk about how to get rid of gnats on plants and the best ways to keep fungus gnats away further down this blog.
Monstera leaves Photo by Jeremy Lee on Unsplash
It starts with just a few tiny flying specks you notice darting around your beloved houseplants Upon closer inspection, you realize they are small flies that seem to be living in the potting soil Annoyed, you shoo them away only to have more appear whenever you water your plants.
If this scenario sounds familiar, you likely have a fungus gnat infestation. While they look like miniature mosquitos, these common yet bothersome insects are not at all related. Getting rid of fungus gnats takes some persistence, but is very doable with the right techniques.
In this comprehensive guide, we’ll cover everything you need to know about identifying, preventing, and safely eliminating fungus gnats from houseplants. No more pesky flies bothering your indoor oasis!
What Exactly Are Those Tiny Flies Buzzing Around Houseplants?
Fungus gnats are tiny flying insects about 1/8 inch long that look remarkably similar to mosquitos. However, they do not bite humans or pets.
These delicate black flies with long legs get their name from their affinity for damp soil that contains fungi and decaying organic matter. This is typically found in the surface layer of potting mix where houseplants grow.
While adult fungus gnats don’t directly harm plants, their larvae feed on plant roots and can injure seedlings or small plants. The larvae are tiny white worms about 1⁄4 inch long found burrowing through moist soil.
Fungus gnats are drawn to indoor plants because of the ideal humid environment and consistent moisture found in potting soil. They lay eggs in top layers of soil and mulch that nurture their development.
If you inspect the soil and see small white larvae wriggling around, there is no doubt fungus gnats have taken up residence. The adults you see flying nearby have emerged from those larvae maturing in the soil.
What Attracts Fungus Gnats to Houseplants?
Fungus gnats are attracted to the damp, decomposing matter in potting mix, so anything that encourages these conditions can draw them in. Here are common culprits that lead to gnat infestations:
- Overwatering plants and letting pots sit in a water-filled saucer
- Using improperly sterilized garden soil indoors
- Allowing thick layers of mulch or debris to accumulate on the soil
- Leaving fallen and decaying leaves or dead plants in place
- Poor drainage leading to soggy soil
- High ambient humidity around plants
- Dark conditions since gnats shy away from light
Keeping soil consistently moist by watering too often or not letting excess drain out creates an environment where gnats thrive. Good potting practices that avoid these issues are key to preventing gnat problems.
How to Prevent Fungus Gnats in Houseplants
Stop fungus gnats from invading your houseplants by following these proactive steps:
- Allow soil to dry out moderately between waterings. Avoid overwatering.
- Remove excess water that collects in drip trays and cache pots. Don’t let plants sit in water.
- Use fresh, sterile potting mixes instead of garden soil which can harbor gnats.
- Apply an inch layer of sand or gravel as a top dressing mulch to deter adults from laying eggs.
- Prune off dead leaves and stems that can decompose and feed larvae.
- Clean up fallen leaves, debris, and dead plants regularly.
- Improve drainage by adding perlite or small stones to soil.
- Grow houseplants with good air circulation and light which gnats avoid.
- Inspect new plants closely before bringing them home.
- Apply beneficial nematodes to soil as a preventive measure.
It’s much easier to stop an infestation before it starts! Adopting these simple practices makes your plants far less appealing to fungus gnats.
How to Get Rid of Existing Fungus Gnat Infestations
If those pesky flies are already buzzing around your plants, take action to kick them out fast using these techniques:
Allow Soil to Dry Out
Since fungus gnat larvae require moisture, allowing soil to dry out more between waterings helps eliminate them. Wait until the top inch of soil is dry before watering again.
Use Sticky Traps
Yellow sticky traps lure adult gnats looking for a place to lay eggs. Stick traps into soil or suspend just above the surface. Replace frequently as they fill up with trapped gnats.
Apply a Sand or Gravel Mulch Layer
Covering soil with a 1 inch layer of sand, gravel, small stones, or horticultural grit prevents adults from reaching the soil to deposit eggs.
Treat Soil with BTI (Bacillus thuringiensis israelensis)
This natural bacteria kills gnat larvae but is safe for plants. Apply as a soil drench every 5-7 days until adults are gone. BTI is sold under brand names like Mosquito Bits, Gnatrol, etc.
Use Horticultural Oil Sprays
Lightly misting plants and soil with neem, horticultural, or insecticidal oils smothers both larvae and adults on contact. Apply weekly for 2-3 weeks.
Apply Beneficial Nematodes
Microscopic worms kill gnat larvae by infecting them with a lethal bacteria. Use Steinernema feltiae species every 4 weeks until fungus gnats disappear.
Repot Plants with Fresh Soil
For severe infestations, remove all old potting mix, rinse roots, and repot plants in sterile soil to fully eliminate fungus gnat larvae.
Discard Heavily Infested Plants
In extreme cases, it may be better to discard badly infested plants and start over fresh rather than trying to save them.
With persistence using these techniques, you can annihilate recurring or severe fungus gnat infestations. Be vigilant about preventing their return by adopting good watering and soil practices.
Natural Predators That Eat Fungus Gnats
In addition to conventional control methods, certain beneficial predatory insects and mites can be used to biologically control fungus gnats as part of an IPM (integrated pest management) approach:
Rove Beetles: These ground-dwelling predators feed on gnat larvae in soil. Dalotia coriaria is a species used in greenhouses and indoor plantscapes.
Predatory Mites: Several mite species like Hypoaspis miles and Stratiolaelaps scimitus consume fungus gnat larvae and eggs. They live in the soil.
Nematodes: As mentioned above, beneficial entomopathogenic nematodes parasitize and kill gnat larvae. The species Steinernema feltiae is effective.
Predatory Thrips: Tiny thrips like the banded greenhouse thrips (Aeolothrips spp.) prey on fungus gnat larvae and eggs in potting soil.
These biocontrol organisms can be alternated or combined with other methods for enhanced fungus gnat management. Speak to your local garden center for options.
When Do Fungus Gnats Tend to Be Most Problematic?
Fungus gnats often first become evident on houseplants brought outdoors for the summer. Wet soil and spilling water makes pots an attractive breeding ground.
Plants kept outdoors may then develop gnat infestations that you only notice upon moving them back inside for winter. So carefully check all houseplants before bringing them indoors.
Fungus gnats can successfully reproduce year-round on indoor plants. But they tend to reach peak populations in spring and fall when humidity is higher. Be especially vigilant about watering properly during these times.
If you stay on top of the situation through preventive measures and promptly eliminate new infestations, fungus gnats don’t have to take over your houseplants.
A few flying around the plants is usually nothing to worry about. But don’t let populations grow out of control. Stay proactive and banish fungus gnats from your indoor plant paradise for good!
How To Get Rid Of Gnats in Plants Naturally
One way to keep gnats away from houseplants that I don’t see suggested enough is to repot your plant, especially if you just bought it. Many plants in big box stores are potted in potting soil that is very dense. This is perfect for fungus gnat larvae to lay their eggs.
Satin pothos on Cactrella trellis from Treleaf
Next, you need to buy a bag of nice quality fresh soil. Ive notice a number of mainstream potting soil bags already infested with gnats and thrips.
Repotting that plant is one of the most effective ways of ridding fungus gnats. This eradicates all the larval stage.
Plants being repotted Photo by vadim kaipov on Unsplash
Mix equal parts of water and hydrogen peroxide. Use this solution for your next watering session. The hydrogen peroxide will target the larvae but not injure your plant. Hydrogen peroxide will also help with any root rot. The fungus gnat larvae will usually be gone in 1-2 waterings. Make sure to follow up with fertilizer. While hydrogen peroxide is great for targeting gnats it will also target any good bacteria as well.
What are fungus gnats?
Fungus gnats are like tiny mosquitoes part of the Bradysia species. Their bodies are small (less than fruit flies and thrips), their wings can be clear or gray, and they have antennae. Fungus gnats lay eggs in organic matter, like soil. The adults can lay up to 200 eggs in the first inch of soil. These fungus gnat eggs will hatch in three to four weeks. The gnats will then start eating fungi, dead plants, and sometimes even plant roots. Adult fungus gnats dont feed and cant bite, theyre typically weak fliers and only live 7-10 days.
Prayer plant “Lemon Lime” Photo by Madison Inouye
Fungus gnat infestation usually happen in the transition from winter to spring and from summer to fall. Fungus gnat adults can live in the soil of any houseplant that was left outside during the growing season from summer to fall. When these houseplants are brought back inside, population will drastically increase due to the warmer temperatures in houses.
