Last Updated on August 1, 2022
Oh, shoot. They are back. There are tiny black insects swirling around your potplants and they are up to no good, you just know it. Dealing with fungus gnats can be frustrating because they are so persistent. But if you are looking for solutions, then this article is for you. Our guide explains what these goobers want, how you can squash an infestation and also, how to avoid future ones.
Table of Contents
What Are Fungus Gnats?
Fungus gnats are tiny flies that resemble mosquitoes. An important part of their life cycle depends on the fungi that exist in the soil of potplants – hence the unusual name. The adult gnats will lay up to 200 eggs in the soil and within roughly 3 weeks, those that hatch will become adults themselves and continue the cycle.
How Gnats Can Damage Your Plants
When you are new to plant problems, one might be forgiven for thinking that these gnats are annoying at most and harmless at best. However, seasoned plant parents know that when this pest knocks on your door there is real cause for concern. Fungus gnats might seem tiny and incapable of damaging anything but in the long run, they can wreak havoc with your plants.
If this is the first time that you are dealing with gnats, the danger does not lie with the adult flies. Nope. It’s their unruly kids. Once the eggs hatch, the larvae get hungry and that’s where the problems begin. They mostly feed on fungi but very often, they decide to chew on plant roots instead. This can lead to irreversible damage or make the plants vulnerable to root rot.
What Causes a Fungus Gnat Infestation?
It is no accident that they have chosen your Delicious Monster and not your cactus collection. Most novices know that cacti need less moisture but sometimes, even an experienced plant parent can give their other houseplants (like the Delicious Monster) too much water. Therein lies the attraction for fungus gnats – they love consistently wet soil.
Your plant cannot catch gnats from other infested plants. The problem is not caused by a disease or pests that simply migrate from one pot to the next available neighbor. When you notice these black insects buzzing around a plant, there is one cause and one cause alone. Overwatering.
There is a silver lining here! With such a simple cause, the solution to prevent future outbreaks is just as easy. You simply have to reduce the frequency of your plant’s watering schedule which will not only stop gnats but also other H2O-related horrors (for example, root rot).
How to Rescue Your Gnat-Infested Plant
The good news is that fungus gnats are not the end of the road. However, it can be the thing that destroys your plant if no action is taken for a long time. Let’s look at what you can do today to help your houseplants from any current and future gnat invasions!
Allow the Plant to Dry Out
If your plant is currently besieged with flies, the first thing to do is to stop watering it altogether. Even when the topsoil looks dry, the gnats are not lying – the soil situated lower down in the container is definitely too wet. This can happen when the pot does not have enough drainage holes or the pot’s design causes water to pool at the bottom. Many of the cheaper ornamental pots have this problem.
Allowing the soil to dry out completely is a long process and possibly dangerous to the plant. After all, at one point it might actually get thirsty and start to wilt. There is another method that might help if you don’t want to play this guessing game.
- Get a new bag of potting soil and a pot that has proper drainage.
- If the new pot is second-hand, sterilize the container first.
- Gently remove the plant from the old pot.
- Remove most of the moist soil but keep the rootball covered.
- Check for signs of root rot. Here are the best tips for treating root rot.
- Repot the plant using the new soil and container.
- Water lightly. Stick to a reduced watering schedule.
Loosen The Soil
Some potting soils are designed to be well-draining but over time, the bits and pieces can settle and become more compacted. Unfortunately, this robs the soil of its ability to allow the water to run through. As a result, the soil becomes more waterlogged and invites problems like rot and fungus gnats.
You can decrease the chances of an infestation by loosening the soil. Go down a good depth and wiggle the soil a bit. You can use chopsticks, toothpicks or even a knitting needle. But whatever you use, be very careful not to damage the roots.
Change the Way You Water
Gnats are initially attracted to wet topsoil – so use this against them! Instead of watering your plants like you usually do, place the container in a dish of water and let the plant soak up the water. This method gives the roots the water that they need while also keeping the upper part of the soil dry. This, in turn, makes the gnats more reluctant to move in and lay their eggs.
Beware the Hardcore Gnats
Sometimes, it is not enough to stop watering your plants from above. Although exceptionally rare, a few gardeners have reported that gnats can enter the drainage holes of a container to seek out the moist soil.
The odds of this happening are very small. But if you don’t want to take that gamble, simply allow your plant to expel the excess water after soaking and then place the pot on a surface that seals the bottom of the pot without blocking the drainage holes. A large curved plate is perfect for this.
Block Gnats From Laying Eggs
If you prefer watering from above or want another layer of protection, then this tip is for you. This simple technique is very effective! Simply create a barrier between the adult gnats and the soil they need as a nesting site. You can do this by adding a layer of gravel, fine sand or even decorative pebbles.
Trap Gnats with Vinegar
For some reason, gnats adore the fragrance of vinegar. Indeed, the jaw-clenching condiment is gold when it comes to controlling the adult population in your home. Take a saucer, fill it with vinegar and place the dish near your potplants. As the days go by, plenty of gnats will get trapped in the vinegar.
Q: Can I use cinnamon to control fungus gnats?
Yes, in theory. Cinnamon is a natural fungicide but whether it can effectively repel fungus gnats remains debatable. If you want to give it a shot, simply sprinkle a layer of cinnamon around the plant when the soil is dry.
Q: Do fungus gnats carry diseases?
No, fungus gnats do not carry any diseases that might affect you, your family or your pets. They also do not carry plant diseases. However, these insects’ larvae can weaken your plants and make them more vulnerable to illness.
Q: Can I really use sticky notes to control fungus gnats?
Yes, you can use sticky notes to catch adult gnats. You can buy them from garden centres or even use sticky notes that are sold as stationary. Place the note on the soil of the affected plant, sticky side up. Gnats are attracted to the color yellow, so use this shade to catch the most insects.
Q: When do fungus gnats appear?
Fungus gnats are more noticeable during the warmer seasons. However, they also appear during the late fall and throughout winter when potplants are brought indoors where the conditions are warmer.
Q: Can my potting soil become infected before I use it?
Yes, fungus gnats are not attracted to plants. They are attracted to moist soil wherever they can find it. Whether that soil is in an open bag or a container with a plant, the gnats will lay their eggs without discrimination. For this reason, securely close a bag of soil after opening it for the first time.
Q: My vinegar trap is not really working. What am I doing wrong?
Sometimes, the gnats prefer something a little different. You can try cider instead of vinegar. Another good blend is vinegar mixed with a sweet ingredient. Effective sweeteners to add to your trap include a spoon of sugar or a dash of sweet-smelling dishwash liquid.