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Avoiding Indoor Plant Infestation: Fungus Gnats

Avoiding Indoor Plant Infestation: Fungus Gnats

Pests are always a concern when it comes to the beauty and life of plants. Fungus gnats, although harmless to humans, are one pest that causes a lot of trouble for plant parents. These small gnats are about the size of fruit flies with the appearance of a mosquito and are notorious for planting eggs in houseplant soil.

Adult fungus gnats are mostly an annoyance, but the larvae may feed off organic matter in the soil and prevent your plant from flourishing. Once you get an infestation of fungus gnats, they are likely to stick around for a while. Make sure before all else to isolate your infected plant from others; it will be much more manageable to eliminate these pests from just one plant as opposed to a dozen! Here are some easy fixes to eliminate fungus gnats from your home.

Insect Spray

Insects can cause significant damage to houseplants by feeding on their sap, leaves, stems, or roots. This can lead to stunted growth, discolored leaves, and in severe cases, the death of the plant. Safe insecticides help in controlling these pests, ensuring the health and vitality of the plants.

Traditional insecticides often contain chemicals that can be harmful to humans and pets if ingested or inhaled. Safe insecticides, on the other hand, are designed to be non-toxic or minimally toxic, reducing the risk of health issues for people and animals in the home. Often easier to use safely in the confined space of a home, safe insecticides typically require fewer precautions than more toxic alternatives and are more forgiving in case of accidental misuse. The use of chemical insecticides indoors can deteriorate the air quality within a home. Safe insecticides are often less volatile and do not release harmful fumes, contributing to a healthier indoor environment.

As well, many conventional insecticides have a negative impact on the environment, harming beneficial insects and wildlife, and contaminating soil and water sources. Environmentally safe insecticides are formulated to be biodegradable and less harmful to non-target organisms, thus protecting the broader ecosystem. Overuse of traditional chemical insecticides can lead to pests developing resistance, making them harder to control over time. Using safe and varied methods of pest control, including biological controls and safer chemical options, can reduce the chance of resistance developing.

Bio Insecticide Indoor/Outdoor Concentrate from Grove

This option from Arber uses biopesticides in place of chemical pesticides, making it safer for the environment, plant parents, and of course the plant itself. Because of this, it is safe to use on any plant including vegetables! As it is a concentrate, follow the instructions on the bottle to ensure proper dilution and usage.

Reduce Moisture

Fungus gnats thrive off moisture, so one of your first steps should be to make sure your plant is not overly moist. By not overwatering your plants, you can make your plant uninhabitable for these pests and kill any larvae that are already living in the soil. Here are some tips to controlling the moisture level in and around your plant:

Proper Watering Techniques:

Over-watering is a common cause of high humidity around plants. Water your plants only when necessary, based on their specific needs. Use your finger to check the soil moisture; water only if the top inch of soil feels dry.

Improve Air Circulation:

Good air circulation is key in reducing humidity. Place plants in a well-ventilated area or use a small fan to circulate air around them. This not only reduces humidity but also helps in preventing fungal diseases.

Use a Dehumidifier:

In naturally humid environments, or during certain times of the year, using a dehumidifier in the room where your houseplants are kept can help control the overall humidity levels. As well, grow lights, if used correctly, can contribute to a stable environment with controlled humidity levels. Some grow lights may increase the ambient temperature slightly, which can help in drying out the top layer of soil more quickly, making it less attractive to fungus gnats. We recommend the Grove™ bar light grow fixture, perfect for illuminating tight corners!

Space Plants Appropriately:

Crowding plants together can trap moisture and raise humidity levels. Ensure there is enough space between your houseplants to allow air to flow freely around them.

Avoid Misting if Unnecessary:

While some plants benefit from occasional misting, doing it excessively or with plants that don't require it can raise humidity levels unnecessarily. Understand the needs of your plants before deciding to mist them.

Drainage is Key:

Make sure all your plant pots have adequate drainage holes. Excess water should be able to drain out of the pot, preventing water from pooling at the bottom and increasing humidity.

Use Terracotta Pots:

Terracotta pots are porous and can help absorb excess moisture from the soil, which can be beneficial in managing soil and ambient humidity.

Regular Maintenance:

Regularly remove any fallen or dead leaves from the soil surface and around the pot. This not only keeps the plant healthy but also prevents mold growth, which can increase humidity.

Use Gravel Trays:

Placing gravel trays under plant pots can help catch excess water and increase the evaporation rate, reducing overall humidity levels. Make sure to empty the tray regularly after watering to minimize the moisture surrounding your plant.

Select the Right Location:

Avoid placing plants in naturally damp areas of your home, like basements or laundry rooms, unless those plants thrive in high humidity. The Aspect™ hanging pendant grow light is a great option for you to place your plant freely and optimally for growth in a suitable space.

Neem Oil

Neem Oil Concentrate from Safer Brand

Neem oil is a great solution to try out, especially if you are a plant parent that may already have some around the house! This natural pesticide is popular for pest control in many houseplants and is definitely worth giving a shot to control fungus gnats. Try soaking the top few inches of your soil in neem oil to kill the larvae without causing harm to your plant.

Neem oil is derived from the seeds of the neem tree (Azadirachta indica), a natural product that is safer for use around humans and pets compared to synthetic pesticides. For those who prefer organic gardening practices, neem oil is an ideal choice, as it aligns with organic agricultural standards. It is effective against a wide range of common houseplant pests, such as aphids, spider mites, scale, whiteflies, and mealybugs, without the need for multiple different products.

Neem oil is also biodegradable and breaks down quickly, reducing the risk of environmental pollution and harm to non-target species, unlike some chemical pesticides. In addition to killing pests, neem oil also acts as a repellent, deterring new pests from infesting the plants.

Neem oil even has fungicidal benefits and can help in controlling common fungal problems like powdery mildew and rust, making it a dual-purpose solution for plant health. Some formulations of neem oil can be absorbed by the plant, providing internal defense against pests and reducing the need for frequent applications.

Pests are less likely to develop resistance to neem oil compared to synthetic pesticides, as it acts in multiple ways to control pests, including disrupting their hormonal systems and inhibiting feeding and reproduction. When applied correctly, neem oil is less harmful to beneficial insects like bees and ladybugs, especially when they are not directly sprayed, as it primarily targets pest insects that chew or suck on the leaves.

Neem oil is relatively easy to use. It is typically mixed with water (and sometimes a mild soap to help it mix and stick to leaves) and sprayed directly onto the foliage of plants.

Raw Potatoes

Raw potatoes might just be able to save your plant from fungus gnat larvae! Fungus gnat larvae are attracted to raw potato slices primarily due to two reasons: moisture content and the organic material available in the potato. Fungus gnats, particularly their larvae, thrive in moist environments. A raw potato slice naturally contains a high level of moisture, which creates an appealing habitat for these larvae. Potatoes, being rich in starches and other organic compounds, then provide a suitable food source for them after they have burrowed into the vegetable.

To create these potato slice “decoys,” chop up a raw potato into small ½-inch chunks and place them close to each other on the surface of your soil. The larvae will be attracted to the raw potato and make their way to the surface to eat it. After a few hours, you should find some larvae feeding on the underside of your potato slice! If your slice is completely covered, you know you have an intense infestation and you’ll need to replace and check on your slices more often. Keep chopping raw potatoes and disposing of them until the larvae are gone.

Sticky Traps

Sticky Traps from Amazon

Sticky traps are an easy fix for fungus gnats along with any other similar-sized pests. These traps can be placed directly into the soil and as gnats fly around your plant, they will get stuck on the trap. The stickiness lasts for months and they are waterproof, so no need to worry about removing them for watering. Sticky traps are a great option for eliminating adult fungus gnats to prevent them from laying more eggs in the soil.

Top Dress Your Soil

Fungus gnat larvae tend to live in the top few inches of soil, so they are easy to target directly. A great way to stop adult gnats from interacting with the soil is by adding a layer of another medium atop your soil. There are a few different choices here, but sand seems to be a great option. Because of the size of each grain, the sand prevents adult fungus gnats from accessing the soil, eliminating the opportunity to lay eggs while still allowing watering to take place. Water can also easily pass through the sand to the soil to make sure your plant is still getting the love it needs. This method also keeps the larvae in the soil so they cannot escape as adult gnats. For this option, make sure the sand is covering all of the soil, from the roots to the edges of the pot, and is roughly ½ inch deep.

Apple Cider Vinegar

Apple Cider Vinegar by Bragg

Another way to capture adult fungus gnats is with apple cider vinegar. In a shallow container, mix apple cider vinegar to attract the gnats with a couple of drops of dish soap to prevent the gnats from sitting on the surface of the vinegar. Cover this concoction with plastic wrap and create large enough holes for the gnats to fit through. Once they make their way past the plastic wrap, they will be unable to escape the liquid mix, preventing them from pestering your plants and laying more eggs.


This may sound like a ludicrous idea but trust us. Nematodes are tiny worms that, when placed in your infected soil, will quickly and effectively eradicate fungus gnat larvae. There are some technicalities as to the most effective way to inject the nematodes into your soil, but they typically are purchased in a solution that will need to be incorporated into the soil for best results. Fighting an insect infestation with another insect might sound counterintuitive, but this method has been successfully used for years!

Remember, if you opt for this form of pest control, nematodes need a moist soil environment and appropriate temperatures (typically between 60°F and 90°F). If conditions are too dry, too cold, or too hot, the nematodes may not survive or be as effective. Nematodes are living organisms and have a limited shelf life. They need to be stored properly (usually refrigerated) and used within a certain timeframe, or they may lose their effectiveness.


Fungus gnats are irritating, and they can damage your plants, but this doesn’t mean you need to ditch your whole collection if you notice them popping up! Just evaluate your options, and act fast!