How to Get Rid of Fungus Gnats: Effective Methods and Prevention Tips for Indoor + Outdoor Plants

Written by: Brianne Dela Cruz



Time to read 3 min

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Fungus gnats are tiny flies that can kill seedlings and potted plants. Fungus gnats thrive in wet seedling trays in humid greenhouses as well as compost and wet decaying organic matter. Adult fungus gnats lay their eggs in the soil and carry disease on their legs, transferring disease from one plant to another. Fungus gnat larvae attack plant roots and sucks out the nutrients, which weakens the plant and makes it more susceptible to dying from disease.

Key non-toxic ingredients in Arber’s organic biological products target fungus gnats and larvae to control and prevent outbreaks, keeping your potted plants or seedlings thriving. 

How to Prevent & Get Rid of Fungus Gnats

To control a fungus gnat infestation:

  • Step 1:  Let your pots dry out.
  • Step 2: Once the soil dries out, soak the soil and spritz the leaves with a combination of .25 oz of  Bio Insecticide and .25 oz of Bio Fungicide. Then follow up with an application of diluted Plant Food to nourish plants.
  • Step 3:  Repeat this process every 5-7 days until the problem is resolved.

To prevent a fungus gnat infestation:

  • Step 1:  Mix a combination of 0.25oz of Bio Insecticide and Bio Fungicide with 32oz of water
  • Step 2:  Spritz the foliage and soak the soil every 10-14 days for general wellness and fungus gnat prevention
  • Step 3: Nourish with Plant Food during alternating weeks of treatment. 

What do fungus gnats look like?

Fungus gnats are tiny flies that infest soil, potting mixes, and decaying organic matter, like active compost. Fungus gnats are dark, delicate-looking flies that look a lot like tiny mosquitoes. These pests are usually a sign that soil is overwatered and too wet. Females lay tiny eggs in moist organic debris or potting soil. Larvae have a shiny black head and a long, whitish-to-clear, legless body. 

Are fungus gnats bad for plants?

Adult fungus gnats are generally harmful to mature and healthy plants, however the larvae are harmful to potted plants and can destroy tender seedlings because they feed on roots and drain plants of their nutrients. A bad infestation can certainly weaken a mature plant and make it more susceptible to disease. 

Where do fungus gnats come from? 

Fungus gnat larvae reside in potting soil. Their populations can grow rapidly in moist greenhouse conditions, and they can be transferred outside or to pots when infested plants are transplanted.

How do fungus gnats harm plants?

Adult gnats lay their eggs on the root hairs of plants inside the soil, and as that larva grows it sucks the nutrients out of the plants roots. When the gnat matures into an adult they’re weak flyers, so they walk across the surface of the soil. Adult gnats carry disease on their legs and transfer that disease from plant to plant as they walk. When fungus gnats show up, there are three problems that need to be addressed: 1) the insects, 2) the disease they are spreading, and 3) the depleted nutrients.

How to prevent & get rid of fungus gnats?

Fungus gnats are attracted to the color yellow and that's why a lot of people will hang sticky paper next to seedlings to capture fungus gnats. But that method doesn’t address the other problems caused by these pesky insects, such as the nutrient deficiency, damaged roots or spread of disease. Arber has three products that address all the problems caused by fungus gnats. Here are the key active ingredients in Arber organic biologicals that target fungus gnats. To prevent and control fungus gnats, follow our treatment plan above. 

  1. Bio Insecticide contains a naturally occurring and non-toxic strain of bacteria, called Burkholderia strain A369, which stops the adult gnats and larvae from feeding on the plant. It also stimulates root hair growth so the plant can begin to heal.
  1. Bio Fungicide contains another non-toxic and naturally occurring strain of bacteria, called Bacillus, that stops the disease. Bacillus works by producing proteins that stop grown fungus gnats on the surface of the soil, as well as the larvae that are in the soil feeding on plant root hairs. 
  1. Plant Food is an organic liquid fertilizer concentrate that provides much needed nutrients to the healing plant.  

The combination of all three organic blends benefit the whole plant and targets the effects of fungus gnats and other pest and disease problems.