Fungus gnats. Just the name is enough to make any plant lover cringe. These tiny, annoying flies can quickly turn your indoor jungle into a buzzing nightmare. If you’re like many plant enthusiasts, you’ve probably experienced the sheer frustration of having these pests constantly in your face, hovering around your favorite mugs of tea, and generally making their presence known in the most irritating way possible.
how to kill fungus gnats in indoor house plants
You’re not alone in this battle. Many have tried countless home remedies, from cinnamon to apple cider vinegar, hoping for a quick fix. While some of these might offer temporary relief, they often fall short of completely eradicating the problem. Watering less can help, but risking your plant’s health is hardly a viable long-term solution.
So, what actually works? After battling my own severe fungus gnat infestation, I discovered a simple, two-step method that finally brought me lasting relief. This guide will share that effective solution, along with everything you need to know about fungus gnats and how to keep them away for good.
Are Fungus Gnats Harmful to Your Plants?
The good news is that a small number of fungus gnats are more of a nuisance to you than a threat to your plants. However, don’t underestimate them. While the adult gnats are mostly just annoying, it’s their larvae that can cause problems, especially when infestations become large.
Fungus gnat larvae thrive in moist soil rich in organic matter. If you tend to overwater your plants, particularly during warmer months, you’re essentially creating the perfect breeding ground for these pests. While a minor infestation might seem harmless, a large population of larvae can start feeding on your plant’s roots when their primary food source (organic matter) becomes scarce.
This root feeding can be particularly damaging to seedlings, new cuttings, and younger plants, stunting their growth and overall health. And unlike some pests that disappear with the changing seasons, fungus gnats can persist throughout the winter in heated homes, making it essential to address the problem proactively rather than waiting it out.
Identifying Fungus Gnats: The Potato Test
If you’re unsure whether you’re dealing with fungus gnats or another type of small flying insect, there are a few key characteristics to look for. Fungus gnats are about the size of a fruit fly, but they resemble tiny mosquitoes in appearance – slender and leggy rather than the rounder, tubbier shape of fruit flies.
Their love for carbon dioxide means you’ll often find them buzzing around your face – you are far more attractive to them than your plants! They don’t bite or make any noise, but their persistent presence is a clear sign of infestation.
If you need further confirmation or want to pinpoint which plant is harboring the gnats, the potato test is a simple and effective method.
Here’s how to perform the potato test:
- Slice a raw potato into a few thin pieces.
- Place the potato slices flat on the soil surface of any plants you suspect are infested.
- Check the potato slices after a few hours.
If you have fungus gnats, you’ll likely find larvae feeding on the potato slices. This confirms their presence and signals that it’s time to take action.
Once you’ve confirmed fungus gnats, discard the potato slices (larvae and all) and start treatment immediately. The method described below is plant-safe and can be used on all your plants if you’re unsure of the infestation’s extent or simply want to be thorough.
The Simple Yet Powerful Method to Eliminate Fungus Gnats
The key to effectively getting rid of fungus gnats is to break their life cycle by targeting both the adult flying gnats and the larvae in the soil simultaneously. This two-pronged approach is far more effective than trying to tackle only one stage of their life cycle.
Essential Supplies for Fungus Gnat Control
You only need two key items for this straightforward method:
- Sticky Traps: To capture adult fungus gnats.
- Mosquito Bits (BTI Granules): To eliminate larvae in the soil.
These products are widely available online and in garden centers. Look for brands like Mosquito Bits or products containing BTI (Bacillus thuringiensis israelensis) as the active ingredient.
Step 1: Sticky Traps for Adult Fungus Gnats
Sticky traps are crucial for reducing the adult fungus gnat population. These traps attract and capture adult gnats, preventing them from laying more eggs and continuing the infestation cycle.
Types of Sticky Traps:
- Green Sticky Traps: These are often designed specifically for indoor plants and are ready to use right out of the package. They tend to be more effective and longer-lasting.
- Yellow Sticky Traps: A more common and often less expensive option. For indoor use, laying them flat on the soil surface is more effective.
How to Use Sticky Traps:
- Green Traps: Simply follow the instructions on the packaging. Typically, this involves attaching the trap to a support stick and placing it in the soil near the plant base.
- Yellow Traps: For enhanced effectiveness indoors, peel off only one side of the protective paper to expose the sticky surface. Cut the traps in half or quarters (before peeling) for easier placement in smaller pots. Lay the traps flat on the soil surface, sticky side up, after watering your plants.
Replace sticky traps every few weeks or when they become covered with gnats or dust. For yellow traps, flip them over after a couple of weeks to utilize the second sticky side for extended use.
Step 2: Mozzie Tea (BTI Treatment) for Fungus Gnat Larvae
While sticky traps deal with adult gnats, Mozzie Tea targets the larvae living in the soil. Mozzie Tea is simply water infused with BTI (Bacillus thuringiensis israelensis) from Mosquito Bits or similar products. BTI is a naturally occurring bacterium that is toxic to mosquito and fungus gnat larvae but harmless to plants, pets, and humans.
Making Mozzie Tea from Mosquito Bits:
- Combine 4 tablespoons of Mosquito Bits with 4.5 liters (approximately 1 gallon) of warm water. Warmer water helps the BTI infuse faster.
- Soak for at least 30 minutes, or up to an hour, in very warm (not boiling) water. This allows the BTI to release into the water.
- Allow the mixture to cool to room temperature before using it to water your plants.
- Strain out the Mosquito Bits granules using a fine mesh sieve or cheesecloth. Alternatively, use a mesh bag to contain the granules during soaking for easy removal.
- Water your plants thoroughly with the Mozzie Tea, ensuring the topsoil is saturated.
Using Mozzie Dunks for Mozzie Tea (Alternative):
If Mosquito Bits are unavailable, you can use Mozzie Dunks. Dunks are designed for larger bodies of water and release BTI slowly.
- Break one Mozzie Dunk into quarters.
- Soak one quarter of a dunk in 4 liters of water overnight (approximately 12 hours). Warm to hot (non-boiling) water aids in breaking down the dunk.
- Remove the undissolved dunk (it can be reused).
- Water your plants with the Mozzie Tea, ensuring the topsoil is saturated.
Watering with Mozzie Tea:
- Top watering is generally more effective as fungus gnat larvae tend to reside in the top layers of soil.
- Bottom watering is possible, but ensure the topsoil becomes moist by allowing the plant to soak for a longer period or by adding a bit of Mozzie Tea to the topsoil.
- You can use Mozzie Tea every time you water your plants until the infestation is under control.
- Mozzie Tea can be used in conjunction with liquid fertilizers. Mix fertilizer after the Mozzie Tea has cooled.
How Long Does Fungus Gnat Treatment Take?
Patience is key when dealing with fungus gnats. Even with this effective method, complete eradication takes time and consistency. A single adult fungus gnat can lay up to 200 eggs, highlighting the importance of eliminating both adults and larvae.
While sticky traps quickly reduce adult populations, Mozzie Tea needs time to work on the larvae life cycle. Fungus gnats can complete their life cycle (egg to adult) in as little as 17 days in ideal conditions, but typically around 3 weeks in summer and longer in cooler weather.
Recommended Treatment Duration:
- Treat for at least 4 weeks even for minor infestations.
- For best results, treat for 8 weeks (2 months) to ensure all life cycles are broken and re-infestation is minimized. Longer treatment is safe for plants.
Frequency of Mozzie Tea Application:
- Drench your plants with Mozzie Tea every time you water, or at least every two weeks.
- Adjust watering frequency as needed for your plants to avoid overwatering and potential root rot. The combination of sticky traps and Mozzie Tea allows for normal watering practices while effectively controlling gnats.
Preventing Fungus Gnats from Returning
Once you’ve successfully eliminated a fungus gnat infestation, prevention is essential to avoid future outbreaks. The combination of Mozzie Bits and sticky traps addresses current problems, but proactive measures are needed for long-term control.
Effective Prevention Strategies:
- Gnat Barrier: Sprinkle a layer of Fungus Gnat Barrier (made from abrasive pumice granules) on the soil surface of susceptible plants (like Peace Lilies or moisture-loving plants). This creates a physical barrier preventing adult gnats from laying eggs in the soil. This is a safer and more effective alternative to diatomaceous earth, which loses effectiveness when wet and can pose risks to pets and children.
- Isolate New Plants: Fungus gnats often hitchhike on new plants. Quarantine new plants for 2-4 weeks before introducing them to your existing collection. This allows time to identify and treat any pests before they spread.
- Sterilize New Soil: Soil stored outdoors can harbor fungus gnat eggs and larvae. Drench new soil with Mozzie Tea or hydrogen peroxide before or after potting to sterilize it and eliminate potential pests.
- Avoid Overwatering: Fungus gnats thrive in consistently moist soil. Allow the topsoil to dry slightly between waterings.
- Don’t Leave Watered Plants Outdoors: Watering plants outdoors creates a perfect invitation for fungus gnats. Bring plants indoors immediately after watering or draining to avoid attracting these pests.
Where Do Fungus Gnats Come From?
Understanding the common sources of fungus gnats helps in preventing infestations:
- New Plants: As mentioned, new plants are a primary source. Eggs and larvae can be present in the soil and hatch after the plant settles in your home.
- Outdoor Soil: Soil stored outside, especially if moist, is highly attractive to fungus gnats and can become infested.
- Bringing Plants Indoors After Being Outside: Leaving freshly watered plants outdoors, even briefly, can attract fungus gnats seeking moist soil to lay eggs.
By understanding these sources and implementing preventive measures, you can significantly reduce the risk of future fungus gnat problems and maintain a pest-free indoor plant environment.
After years of battling these annoying pests, this two-step method has been a game-changer. No more swatting away gnats from my face or fishing them out of my tea! Take control of your fungus gnat problem with this effective strategy and enjoy your plants without the buzz. Share this guide with fellow plant lovers and help them reclaim their indoor jungles!
