Fungus gnats on your plants can be a real bother. Here are some tips to remove fungus gnats from your grow room. – Gro Indoor
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A Complete Solution to Remove Fungus Gnats from your Grow Room

by 09 Apr 2023

A Complete Solution to Remove Fungus Gnats from your Grow Room

Fungus gnats are one of the most common grow room pests. As a grower, you can run into these small black, mosquito-like flies anywhere. Dealing with these pesky bugs can be extremely frustrating as they reproduce quite rapidly. If you delay your first line of action, you might find yourself stuck in a whole lot of trouble.

However, there are several ways to treat a room infested with fungus gnats. From standard pesticides to beneficial insects, protecting your room or garden can actually be pretty simple. But before skipping to that part, it is important to understand what they look like and how they might be a nightmare for your plants.

Understanding Fungus Gnats

A fungus gnat is a tiny black fly that can look like a mosquito. They are also commonly confused with fruit flies. However, under a microscope, they can be easily differentiated from them.

Why fungus gnats become such a headache because they have an endless life cycle, their life starts when adults lay eggs in the soil. These eggs then hatch into larvae, feeding on the root hairs and causing severe damage to the plants. A few days later, these larvae develop into a maggot that cocoons itself. The maggot then develops into an adult fungus gnat. Ultimately, the life cycle repeats itself.

How Does Adult Fungus Gnats Harm your Plants?

The damage caused by fungus gnats is quite deadly as they eat plants from underneath the soil and beneath. In some cases, the larvae feed on the roots, causing irreversible damage. Due to this, plants experience inferior growth. The leaves also start turning yellow as water and nutrients are unable to reach upwards. Unless measures are in place to treat the plant, they eventually die.

What Causes Fungus Gnats in your Plants?

There are several reasons why these flies keep buzzing around your yield. They often travel indoors on potted plants or cut garden flowers. Another possible explanation is moisture, which may come from leaky pipes in your basement, malfunctioning appliance, or other sources. Further overwatering and soggy soil also invites fungal gnats.

High CO2 Concentration

For a while, people who have been growing plants tend to introduce CO2 to their grow tent for supercharging plant growth. CO2 is an excellent way of maximizing your yield, increasing your buds' potency, and decreasing your time till the harvest. However, this might also be one of the causes that fungus gnats swarm your plants.

High CO2 concentration attracts fungus gnats, and if they are already present in your plants, it will only add to your troubles. You can control them by turning off the CO2 producers until the fungus gnats are all wiped out.

If you are hoping to try out CO2 for your plants, check out our guide on using CO2 in Grow tent/ Grow room.


One of the leading causes of fungus gnats is giving your plants an excess supply of water. New growers are sometimes too enthusiastic about feeding their plants, which often leads to waterlogging. Wet and warm soil is the perfect environment for fungus gnats. Once they lay their eggs, the trouble has just begun.

Hence, ensuring that your plants get the right water amount is significant for preventing fungus gnats. If you are new to growing, read on: Things you need to Know about Watering Plants, for tips on adequately watering your plant.

Poor Ventilation

Your ventilation system and the atmosphere around you contribute significantly to staving off fungus gnats and other pesticides from your grow room. If the room's atmosphere isn't optimal, there could be more trouble than you can imagine.

It will help if you check the humidity, air circulation, and temperature, all of which can be controlled through a ventilation system. Without ventilation, there are more chances for pests and bugs to grow, so it is crucial to circulate air in your grow room with a fan.

A ventilation system brings in clean and fresh air while simultaneously removing stinky, hot air. On the flip side, it can bring in harmful contaminants and several pests if the system does not have proper sealing. It is recommended to seal your system with a HEPA intake filter to prevent harmful pollutants from taking over your grow room.

If you are worried about the ventilation system in your grow room, take a look at: Things you need to know about the Grow Room’s Atmosphere and Ventilation to figure out the best possible way.

Type of Soil

There are certain types of soils that favor the growth of fungus gnats more than others. Even though these soils have several benefits, they might also cause a fungus gnat infestation. Growers who use mixes such as coco, peat, or compost, should be extra careful of fungus gnats.

Don't forget to check our guide on: Best Soil for Indoor and Outdoor Plants, and learn the different soil types for growing your plants.

Getting Rid of Fungus Gnats

There is more than just one way of treating your plants if your grow room falls victim to a fungus gnat infestation. The best strategy is to take precautionary measures, which significantly reduce your chance of dealing with the problem.

Get rid of the infestation with:


Insecticides are the easiest, most effective way to get rid of pesky fungus gnats. There are several items that you can use, and most of them are available at

Here are some of the recommendations.

Hydro Organics Gnats

Hydro Organics Gnats is explicitly designed to fight off fungus gnats. Hydro Organics Gnats can be used as a soil drench and foliar spray. If you intend to kill even the adult gnats and the eggs and larvae, it is best to use both methods.

Neem Oil

Neem Oil is like a natural insecticide, which is used for treating several infestations. It can either be spread into the soil or applied as a foliar spray. The best technique is to use a misting sprayer, as it kills on contact. Ensure covering all the bugs for the maximum impact.

Yellow Colored Sticky Fly Traps

Sticky fly traps, preferably in yellow color, should be your first line of defense. Even though it makes no sense, still, fungus gnats are drawn to the yellow color. By hanging a few of these around your grow room, you can catch fungus gnats quite easily. These fly traps also help in slowing down the infestation process and stop it from spreading further.

However, this doesn't mean that these fly traps are enough on their own. It is better to hang these traps in your grow room even before you spot an infestation. This will help you in alerting that an infestation might be starting.

Soil Amendments

Fungus gnats do most of the damage to the soil and roots. This is why you should take extreme measures in the soil.

There are several ways to prevent the soil from getting damaged and eliminate the bugs entirely. Here is one of them:

Diatomaceous Earth

Diatomaceous Earth is formed from fossilized remains of marine phytoplankton. You can put this rock on the top of your soil, and it will act like a little shard of glass, cutting bugs that crawl around open. These bugs then dry out from the inside and eventually die.

Diatomaceous Earth is perfect, not just for disrupting fungus gnats' life cycle but also for preventing the bugs already present in the soil from escaping.

Home Remedies to Fight off Fungus Gnats

Fighting off fungus gnats requires swift action. Therefore, if you don't have any insecticide on hand, some remedies have been proven successful by growers. Let’s discuss them now!

Apple Cider Vinegar

The best way to keep the pesky fungus gnats at bay is with a dash of vinegar. If you don't have any, just dilute it in water and spray it around plants or on windowsills where they may be hiding out!

All you need is to create a mixture of the vinegar with 2 to 3 tablespoons of dish soap. Once you place this mixture around the plants, the bugs will get caught and die.

Hydrogen Peroxide

One of the most effective techniques is using hydrogen peroxide as a soil drench. It helps in killing gnats and their larvae. However, it will also kill any other microbial life in the soil. Even though it's not ideal, it is still better than letting your plants die.

After you bring the infestation under control through hydrogen peroxide, you can reintroduce various beneficial microbes through a compost tea mix.

Beneficial Bugs and Bacteria to Fight with Fungus Gnats

Fighting fire with fire is actually a smart idea in this case. You can introduce certain bacteria and bugs that will attack the fungus gnats and eliminate them from your growth.

Here are a few bacteria that growers have seen success with:

Bacillus thuringiensis

Organic farmers use Bacillus thuringiensis to control insects on crops that are meant to be consumed. BT is also used and endorsed by The World Health Organization to control mosquitoes.

All you have to do is crush the product into powder form and mix it with water. Then apply this mixture to the soil, and eventually, the fungus gnats will die.

If you are willing to try this out, read on: Complete Guide on Beneficial Bugs for Plants.

Beneficial Nematodes

If you are using organic soil, beneficial nematodes are the best option. These microscopic roundworms find and kill over 200 insects that are found in the soil. Besides attacking, they also eat the gnat larvae, which prevents them from reproducing further.

Soilless mediums, too, can benefit from beneficial nematodes. However, they don't work in a sterile hydroponics setting.

The End Notes

Keeping a checklist to ensure that your growth is free from fungus gnats is very important. This will also help you in keeping an eye out for signs of bacteria and other insects regularly.

Above all, don't forget that most of them can be eradicated when these diseases are detected early. If you wish to learn more about problems that you might have to deal with in your growth, don't forget to read: Watch Out for these Common Grow Room Pests and Diseases!

Sep 6th 2022
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