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Today we’re going to talk about one of the most common cannabis pest infestations, fungus gnats, which are also called dark-winged fungus gnats or mushroom flies. They’re scientifically known as Sciaridae, part of the Diptera family. These are one of the hardest to see, yet most disastrous insect infestations. Let’s have a look at how to get rid of fungus gnats.
These insects are quite common in humid and hot areas. This is why they tend to rear their ugly heads when it comes to indoor growing as well as greenhouses. They can also appear in areas with lots of rain or if your plants’ substrate is soaked for too long.
How to get rid of Fungus Gnats | Detecting them
You’ll need to know what fungus gnats look like if you’re going to catch them in the act. They have four different distinct stages; eggs, larvae, pupae and adult fungus gnats. You most likely won’t be able to see them at all until they’re fully grown adult insects and begin flying around your plants.
Adult fungus gnats are usually black, dark grey and sometimes brown. They generally grow between 1.6-3.2mm and have six long legs, which can give them a sort of mosquito-appearance.
The best way to figure out if you have a fungus gnat infestation among your cannabis plants is to place a couple of yellow fly-catching steps near the bottom of your plants. Another easier method is by simply lifting the flowerpot up and letting it fall back down – this will cause them to stir and start flying. They can be quite hard to detect.
How do fungus gnats spread?
Once fungus gnats have started their reproductive cycle, they search for somewhere to lay their eggs, and your plants’ substrate is a great spot. They can lay between 50 and 300 eggs at once, and they only hatch if the humidity and temperature are high enough.
What damage do fungus gnats cause?
Around 48-72 hours after the gnats have laid their eggs in your plants’ substrate, they’ll begin to hatch, causing an infestation that feeds off of your plants’ roots for around 13 days. This, in turn, may cause the infected plants to develop fungi and rot in their roots, which can be thoroughly fatal if not caught in time. They also make it much easier for your plants to become infected by other types of virus.
Another side-effect of this annoying pest is that your plants may stop absorbing nutrients all together due to the fact that they eat at the roots and the follicles used to absorb nutrients and water. If you manage to get rid of your fungus gnat infestation, your plants will re-grow their own root follicles, although if they’re flowering this may not happen.
Fungus gnat infestations tend to put your plants on hold almost entirely. They can also cause a lot more serious problems that can be harder to get rid of.
How to prevent fungus gnats
Like we said, fungus gnats tend to thrive in humid, shady environments that are warm enough. If you want to get off to a good start and avoid having to deal with these gnats at all then you’ll need to take a series of precautions when planting. Try and avoid soaking your substrate, keep the area ventilated and place a thin layer of clay or perlite on top of your substrate to stop the flies from getting in in the first place. We also recommend placing some clay balls at the bottom of your flower pots too. This allows water to train and evaporate much easier from the bottom of the pot, which stops it from accumulating humidity.
Another handy thing that you can do is place yellow fly traps around the bottom/middle of your plants. This can keep any wandering flies under control although it isn’t good enough to get rid of a full infestation. You should use yellow fly trap strips whenever you grow cannabis anyway. They help to keep plenty of different types of flying insects at bay.
If you really want to keep these nasty fungus gnats away from your plants, you can always use Neem cakes or neem flour. All you have to do is mix it in with your plants’ substrate before you actually plant them, or mix it in with the surface layer of substrate and then water so that it filters down through the entire flowerpot. Neem is used in plenty of different cultivations in order to keep your plants’ roots safe.
How to get rid of Fungus Gnats
Once gnats have taken hold of your plants you’ll need to use specific products in order to get rid of them. One of the most effective ways to get rid of them is by using Bacillus Thuringiensis, which is a bacteria that’s also used to get rid of caterpillar infestations.
You can also use other types of nematodes such as Stienemema Feltiae, although they’re a bit delicate to keep alive. If you manage to control the parameters in your grow room properly this can be quite an effective method.
When it comes to other insects you can use a type of Acari insect called Hypoapsis Miles, which is quite a feisty pest. It’s known as the tiger fly, and adult tiger flies absolutely love to show down on fungus gnats. Synacra Paupera is another insect that you can use. It’s a flying insect that infects fungus gnat larvae.
When it comes to using biological means of controlling insect infestations, you’ll need to keep careful control of the parameters surrounding your plants, as all insects need specific parameters to stay alive. If you use this method you won’t be able to use insecticides at all, as you may end up killing off the insects that are trying to help.
