Fungus gnats (also called soil gnats) are probably the most common (and annoying) houseplant pests. The worst part about fungus gnats is that they can infest any plant that is growing in soil. You will notice these indoor plant bugs crawling out of the potting soil or flying around your plant when you water or otherwise disturb the soil. Yuck!
What Are Fungus Gnats?
Fungus gnats are tiny black flying bugs in houseplants soil. You will see them crawling around on top of the soil, or flying around your plants
Fungus gnats live and breed in the soil. Adult gnats will lay eggs in the soil, and the larvae (tiny white worms that are barely visible to the naked eye) will feed on roots and other organic matter in the soil.
Fungus Gnats or Fruit Flies?
Fungus gnats look similar to fruit flies, and I have seen many people mistaken a fungus gnat problem with fruit flies.
Fungus gnats lay their eggs in moist soil where the larvae will hatch and feed on small roots, fungus and other organic matter in the soil. They have no interest in fruit.
If you see tiny black bugs in plant soil, and flying around your plants – those are fungus gnats.
The gnats that are flying around the fruit, or the garbage disposal in your kitchen are fruit flies.
Where Do Fungus Gnats Come From?
A fungus gnat infestation can come from anywhere. The most common ways fungus gnats get into your house are either they’re in the soil of a newly purchased plant, or in a bag of potting mix that you bring indoors.
But fungus gnats can also come in with a plant that was outside during the summer. Heck, they can even fly in through the screen of an open window or door.
How to Get Rid Of Fungus Gnats In Houseplants Soil
Fungus gnats are difficult to eliminate if you have a large number of indoor plants. The adults can easily fly or jump from one plant to the next, laying eggs wherever they find moist soil.
Like fruit flies, the adult fungus gnats only live for a few days. So, once all the larvae are dead, your fungus gnat problem will go away.
There’s no need to resort to toxic synthetic pesticides, fungus gnats can easily be fought using all-natural pest control and pest prevention methods.
1. Control soil moisture – Fungus gnat larvae thrive in moist soil, and they can’t survive in dry soil.
So, the easiest and most effective method of plant gnats control, and ultimately eliminating fungus gnats, is to make sure you never overwater your plants.
Be careful though, you don’t want to allow the soil to dry out completely on most houseplants. Use a soil moisture gauge to help maintain the perfect level of moisture for your houseplants, and get rid of gnats in plant soil.
Indoor plant watering devices also make watering houseplants easier, and help you avoid overwatering so you can get rid of plant gnats.
2. Water plants from the bottom – Fungus gnat larvae live in the top inch of the soil, which tends to stay pretty moist when you water plants from the top.
Bottom watering plants will make it easier to maintain dryer top soil, without risking the overall health of the plant.
To water your plants from the bottom simply pour water into the plants drip tray or cache pot, and allow the plant to soak up the water through the drainage holes.
Never allow your plant to sit in water for too long. Dump out any remaining water after about 30 minutes of soaking.
3. Use yellow houseplant sticky stakes – Putting a yellow sticky trap near the plant is a super safe pest control method that will attract and capture the adult fungus gnats.
This will only be effective to control the adult population, it will not take care of the problem at the source (the larvae).
But yellow sticky traps definitely help to keep the adult fungus gnats from flying around to other plants.
4. Apply organic pest control products – Pour or spray an organic insecticidal soap or a soapy water mix (I use Dr. Bronner’s Baby-mild Liquid Soap) or neem oil mixture into the top of the soil to kill gnats in potted plants. These natural gnat pesticide treatments should be effective after a few applications.
Neem oil works great to kill houseplant pests, and has a residual effect that helps with pest prevention. You can buy neem oil here.
5. Remove the gnat infested soil – Remove the top inch of potting soil and replace it with new, sterile potting soil.
This will remove fungus gnat eggs and larvae, and make it easier to gain the upper hand.
Just keep in mind that gnat eggs in soil could still hatch and mature after you remove it from your plant, so make sure you take it outside to the trash.
6. Use soil covers – Replace the top inch of soil with a layer of sand, gravel or decorative moss soil covers.
This will help control gnats in soil, and deter them from laying eggs. Plus soil covers also add a nice decorative touch.
You could also use a product called Gnatnix, which is a non-toxic soil cover that works great for eradicating fungus gnats.