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Effective Strategies to Prevent and Eliminate Fungus Gnats in Your Indoor Mushroom Garden

Fungus gnats are a relatively uncommon nuisance for indoor mushroom gardeners. However, when they arrive, they cause damage to the mycelium and hinder mushroom growth. While the soil that we sell in our online store is pasteurized, fungus gnats are able to lay their eggs in the soil after you’ve inoculated the soil with mycelium-covered grains as outlined in step 2 of our method for growing mushrooms.

In this blog post, we will explore effective strategies for preventing and ridding your indoor mushroom garden of these pesky pests. With some diligence and proper care, you can keep your mushroom garden healthy and thriving.

What exactly are fungus gnats?

Fungus gnats (Sciaridae and Mycetophilidae families) are tiny, flying insects that are commonly found in and around damp, organic environments, such as indoor mushroom gardens and houseplants.

Adult fungus gnats are generally harmless and measure about 1/16 to 1/8 inch long, with dark-colored, slender bodies and long, delicate legs. The larvae, however, can be problematic for mushroom gardens and plants, as they feed on the organic matter in the substrate, including the mycelium of mushrooms and roots of plants. This feeding can cause stunted growth, yellowing, and wilting, ultimately affecting the health and productivity of the garden.

Fungus gnats are attracted to moisture and decaying organic material, making indoor mushroom gardens an ideal breeding ground if proper care and prevention measures are not implemented.

Top Ways to Prevent and Treat Fungus Gnat Infestations

Sticky Traps

Sticky traps are a popular and effective method for monitoring and controlling various flying pests, including fungus gnats, in indoor gardens and greenhouses. These traps are typically made from a rigid material, such as plastic or cardboard, coated with a highly adhesive, non-toxic substance that captures insects upon contact. Yellow sticky traps are particularly effective against fungus gnats, as the color yellow attracts these pests.

To use sticky traps in your indoor mushroom garden, hang or place them near the garden or directly above the substrate where fungus gnats are most active. The traps will capture adult gnats as they fly around, helping to reduce their population and prevent further breeding. It's important to monitor and replace the traps regularly to maintain their effectiveness. While sticky traps are efficient at trapping adult fungus gnats, they do not address the larvae in the substrate. Therefore, it's essential to use sticky traps in combination with other prevention and control methods to effectively manage fungus gnat infestations in your indoor mushroom garden.

Check out these sticky traps, reasonably priced, on Amazon.

Use Physical Barriers

  • Implement fine mesh screens: Cover your mushroom garden with a fine mesh screen to prevent adult gnats from laying eggs in the soil.

Biological Controls

  • Add carnivorous plants like Drosera, Pinguicula, and Drosophyllum to your home. They are all flypaper traps that can quickly take care of fungus gnats.

Maintain Proper Sanitation and Monitoring

  • Clean up debris: Regularly remove dead or aborted mushrooms after harvest.

  • Monitor your garden regularly: Keep a close eye on your mushroom garden for any signs of fungus gnat infestation. Early detection and intervention can prevent severe damage to your mushrooms.

Use Diatomaceous Earth

  • Apply food-grade diatomaceous earth (DE) by lightly dusting the surface of the soil. DE is a natural, non-toxic substance made from crushed fossils that can help deter fungus gnats by damaging their exoskeletons.

Neem Oil Treatment

  • Neem oil, a natural insecticide, can be used to deter fungus gnats. Mix neem oil with water according to the manufacturer's instructions, and spray it around the lid of your grow kit. This treatment can help prevent adult gnats from laying eggs in your mushroom garden.

Gnat Barriers

  • Create a barrier with a layer of sand or perlite on top of the soil. This can help deter fungus gnats from laying eggs in the soil by making it more difficult for them to access the moist environment they prefer.

  • While this strategy might work, you will need to pasteurize the sand and soil. Even then you may end up with contamination. Use it as a last resort.

Use Essential Oils

  • Some essential oils, such as lavender, eucalyptus, and peppermint, can act as a natural repellent for fungus gnats. Dilute the essential oils in water and spray the mixture around the lid of the grow kit. Be cautious not to overuse these oils, as they can be toxic to plants and fungi in large quantities.

Quarantine New Additions

  • When introducing new plants or materials to your home, keep them separate from your existing mushroom garden for at least two weeks. This quarantine period can help ensure that you don't introduce any fungus gnats or other pests to your mushroom garden.

  • Consider moving your mushroom grow kit to a place in your home with no plants or compost.

Make Your Own Fungus Gnat Trap

DIY fungus gnat trap made from a small container filled with apple cider vinegar and dish soap, covered with plastic wrap and small holes
Homemade Fungus Gnat Trap

Building a simple and effective homemade fungus gnat trap is easy and can be done using common household items.

Here's a step-by-step guide to create a DIY vinegar trap!

Materials needed:

  • A small container or jar (e.g., a mason jar or empty yogurt cup)

  • Apple cider vinegar

  • Liquid dish soap

  • Plastic wrap

  • Rubber band or string

  • A toothpick or fork


  1. Clean the small container or jar to ensure there are no food residues or other contaminants.

  2. Fill the container with about an inch of apple cider vinegar. The vinegar's strong smell attracts fungus gnats.

  3. Add a few drops of liquid dish soap to the vinegar. This breaks the surface tension of the vinegar, making it more difficult for the gnats to escape once they land in the trap.

  4. Cover the container with plastic wrap, securing it tightly with a rubber band or string. Make sure the plastic wrap is taut and has no gaps or holes.

  5. Use a toothpick or fork to poke several small holes in the plastic wrap. These holes should be large enough for the fungus gnats to enter but small enough to make it challenging for them to escape.

  6. Place the DIY vinegar trap near your indoor mushroom garden or in an area where you've noticed fungus gnat activity.

  7. Check the trap regularly and replace the vinegar solution as needed. Dispose of trapped gnats by discarding the vinegar solution and cleaning the container before refilling it.

Remember that this trap mainly targets adult fungus gnats, so it's essential to combine this method with other prevention and control strategies to address the larvae in your indoor mushroom garden.


Remember, prevention is always better than cure. By combining these additional methods with the previously mentioned strategies, you can create a comprehensive plan to keep your indoor mushroom garden free of fungus gnats.

By implementing these prevention and control methods, you can maintain a healthy, fungus-gnat-free indoor mushroom garden. Consistent monitoring and timely action are crucial to the success of these strategies. With proper care and attention, you can enjoy the benefits of a thriving mushroom garden without the frustration of dealing with pesky fungus gnats.


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