Easily Get Rid of Fungus Gnats on Marijuana

Quickly and easily kill fungus gnats in your marijuana grow room. Fungus gnats are a pesky although common annoyance for marijuana growers.   Luckily if you catch fungus gnats early you can avoid the dreaded fungus gnat infestation which can reek havoc on plants especially younger plants.   Therefore continue reading below to learn how to easily get rid of fungus gnats on marijuana

What are Fungus Gnats – Kill Fungus Gnats

Fungus gnats also known as sciarid flies are dark brown / black and have a mosquito like appearance.  Keep in mind these can be hard to see as they are tiny generally can be as thick as a quarter approximately 2mm long.   Fungus gnats thrive in damp environments therefore warm soil that is over watered can serve as a breeding ground for these flies and their larvae.

Fungus gnats feed on decaying plant matter in over watered soil and also this is where they lay their eggs.  These eggs eventually become larvae which happens within the first 2 to 3 inches of top soil.

Fortunately by paying attention to your plants you can catch fungus gnats early which means you can easily kill and prevent fungus gnats from ever coming back.

Why are Fungus Gnats Bad for Marijuana?

Even though fungus gnats prefer fungus and decaying soil they will feed on root hairs and roots of cannabis plants and especially so for younger plants with less hearty root systems.  Overlooking or ignoring fungus gnats can cause slow growth on marijuana plants and even death to young / adolescent cannabis plants.  In fact adult fungus gnats can spread diseases such as pythium that can cause root rot.  For this reason any signs of fungus gnats on marijuana should be taken seriously!

What are the Symptoms of Fungus Gnats?

A fungus gnat infestation can cause all sorts of weird problems for marijuana plants.  Unfortunately, many of the symptoms of a fungus gnat infestation can be confused with nutrient deficiencies,  humidity issues and obviously over watering.  For this reason it is extremely important not to overwater your plants.  As a general pointer the more fungus gnats you can see flying around or left on sticky paper fly traps the worse the fungus gnat infestation.

Fungus Gnats on Marijuana -Fungus gnats and marijuana

How to Kill Fungus Gnats on Marijuana?

First of all, if you have a fungus gnat problem it is probably because the soil is too wet.  Therefore by not over watering you can get rid of fungus gnats quickly.   Plants need water when the first inch of top soil feels dry to the touch.  You can easily determine this by placing your finger in the soil up to the first knuckle.  If the soil feels dry then it is time to water however if damp leave it be until it feels dry.  Ultimately this is not only good watering technique but a way to almost instantly kill any fungus gnat larvae / eggs that may be in the soil.

If you currently have fungus gnats let the soil dry and the gnats will vanish

However if you discover or feel your fungus gnat problem more severe or you have an ongoing fungus gnat infestation take these steps.

Moderate to Serious Fungus Gnat Infestation –  Fungus Gnat Control

Here are a few key steps to quickly kill fungus gnats on marijuana.  Follow these and keep a close eye on your plants.

  1. Put yellow fly paper / sticky cards in your grow room(s).  Fungus gnats absolutely love the color yellow and are attracted to it.   This will trap adult fungus gnats but more importantly serve as an indicator to determine if your fungus gnat control approaches are effective.  As you should see less fungus gnats over time.
  2. Invest in one or two table top fans so that you can keep air circulating over the soil.  This will also help deter fungus gnats from flying around the grow area.
  3. Do not water for a couple days.
  4. Treat the topsoil of your marijuana plants with neem oil by using a pressure sprayer / mister.  This will ensure the neem oil gets evenly distrusted.  It is safe to use neem oil up to a week prior to harvest and it works almost instantly.  Avoid using on bud that is almost ready for harvest as it tends to leave a funky taste.

getting rid fungus gnats - neem oil getting rid of fungus gnats

Additional Approaches for Killing fungus gnats

After taking the above approach for a few days and you are getting little to no improvement then consider using these treatment approaches to help kill fungus gnats.  Like we become resistant or immune to medications specifically antibiotics, fungus gnats operate the same way.  Therefore changing up the treatment plan may be just what the doctor ordered.

      • Diatomaceous Earth –  completely organic insect killer that is all natural made from sea shells.  Essentially this is safe for humans and pets but deadly when it comes to killing fungus gnats.  This works on a microscopic level essentially penetrating the insects exoskeleton which drys them up. Consider using something like a powder duster to evenly distribute the Diatomaceous Earth.
    • Essentria IC3 Insecticide  – Like the others safe for humans and pets.  This is another well known product that will help with getting rid of fungus gnats.  You may have seen this used as a bed bug killer as it works well for that too.
    • SM-90 Plant Growth Fertilizer is also a great option for killing fungus gnats as it extremely healthy for roots.  Used once a week and generally 1 part to 5 parts water.  While the bottle does not directly say it helps kill fungus gnats or bugs, experience has shown it does kill fungus gnat larvae.   You will also need a pressure sprayer for this option to ensure even distribution of chemicals on soil.
    • Hydrogen Peroxide if you don’t have access to anything else try food grade hydrogen peroxide.  It is another method that will focus on the larvae, however do keep in mind this kills the good bacteria too so you will need to compensate.  Admittedly hydrogen peroxide is good to have around for so many things gardening and beyond.

Final Tokes on Killing Fungus Gnats

All though controlling fungus gnats can be annoying it is easy to do with time and attention.  Like many common problems growers face, fungus gnat control is all about prevention.  As the adage says  “an ounce of prevention is worth a pound of cure”  Moreover below you will find some of the best products to help with killing fungus gnats and many other essentials to a pest free grow room.

2-Liter One-Hand Pressure Sprayer, Ergonomic Gardening,2-Liter One-Hand Pressure Sprayer, Ergonomic Gardening,View DetailsHolmes Lil' Blizzard 8-Inch Oscillating Table FanHolmes Lil’ Blizzard 8-Inch Oscillating Table FanView DetailsBed Bug and insect killer, Pro grade, organic and EPA compliantBed Bug and insect killer, Pro grade, organic and EPA compliantView Details5-Pack 7 Gallon Grow Bags /Aeration Fabric Pots w/Handles5-Pack 7 Gallon Grow Bags /Aeration Fabric Pots w/HandlesView DetailsHydrofarm Green Premium Saucer,  hydroponicsHydrofarm Green Premium Saucer,  hydroponicsView DetailsJump Start Hot House with Heat Mat, Tray,Jump Start Hot House with Heat Mat, Tray,View DetailsMykos Xtreme Gardening 721210, 20 lbMykos Xtreme Gardening 721210, 20 lbView DetailsHarvest More Trim Bin - Gray cannabis trim binHarvest More Trim Bin – Gray cannabis trim binView DetailsFoxFarm Ocean Forest Potting Soil, 1.5 cu ftFoxFarm Ocean Forest Potting Soil, 1.5 cu ftView Details

If you continue to experience slowed growth after getting rid of fungus gnats be sure and check for other types of problems like spider mites as those can really cause some problems.  For more information about spider mite control click here.  Additionally you may also want to check into any potential problems with humidity which we discuss the importance of humidity for growing cannabis here.

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