What to do about Fungus Gnats...Whether indoors or outdoors, we have all most likely encountered pests, rodents, or insects. Good & bad, these insects can be a blessing or a curse in your garden. Of all the insects which impact a healthy Cannabis plant, the Fungus Gnat is among the most common of all, right up there with ants, aphids, and fruit flies.
What are they?
The shortest answer is: An Insect.
A bit more in depth answer is: A small, dark, soft-bodied, winged insect, less than a quarter-inch long that resides primarily in the lower regions of the plant.
A proper, scientific answer is:
*Fungus Gnats are also called "dark-winged fungus gnat" in other parts of the world. They are the least-studied of all Diptera Order because they're hard to properly identify, with tens of thousands of species either known or awaiting discovery.
- Kingdom: Animalia
- Phylum: Euarthropoda (Arthropods)
- Class: Insectia
- Order: Diptera
- Family: Sciaridae
What do they do?
Some gnats are pollinators or predators. Problem is, they can carry pythium on their feet, causing a condition known as "damping-off" in seedlings (Terminix).
They are found living in or near the soil in shady, cool, and moist conditions. This is paramount for their success--moisture. Larvae live underneath the first 3" of topsoil. Adults live at the surface, hovering low, either flying or running. Gnats only eat when they're in their larvae or pupate phases; adult gnats do not eat, they only reproduce (Stitch, 2008, pp. 53-55). They feed primarily on roots, including the root tissue itself, and the trichoblasts (root hairs). Apple
Why Are They Here?
Like flies, gnats are attracted to scents like sweet, fruity, and pungent. They also find moisture to be vital, which is why they go right for the eyes, mouth and mucosal surfaces of the body.
A Quick Note on Reproduction
Females begin by ovipositing their eggs in the soil near the plant stem. Within 4 to 10 days, they hatch. Larvae will begin feeding on organic matter, mold, or roots. Next, the larvae enter the soil for their pupate phase, staying underground for 3 weeks. After the 3 weeks, the larvae re-emerge as adult gnats. The entire process, egg to adult: 4 weeks. Each female can lay multiple hundreds of eggs at a time, meaning that once you've spotted flying gnats in your garden, your already behind by at least a month and could potentially face a devastating infestation in a very short time.
How To Exterminate Them
There are actually myriad ways to kill them off. If you've not yet spotted them, Praise God and then proactively work toward keeping it up. If you have spotted them already, there are many easy ways. The following can be used to spray the insects directly, either on or off the plant, indoors or outdoors.
*Elimination is not Prevention*
- Neem Oil
- Beneficial Bacteria
- Soap & Water
- Apple Cider Vinegar + Ceyenne Pepper
- Dawn + Apple Cider Vinegar + Salt
What I mean by this is simply that you can focus your energy in 1 of 2 ways: Extermination or Prevention.
How to Prevent Them
Preventing the gnats from infesting your operation is preferrable to exterminating them because you eliminate the risks the insects bring to the plant altogether, in exchange for the application of either chemicals or organic substances on the plant. So if you have not yet spotted them already, here are a few helpful ideas & recipes, listed in order of importance:
I hope you find this article helpful or enlightening in regards to pest management and plant health & wellness. I've run into issues plenty of times with pests or bugs, both indoors and outdoors, so while I am not the expert, I feel comfortable commenting on these matters. Thanks for reading!
- Ensure proper drying time between waterings as much as the plant will tolerate. Remember: gnats need moisture.
- Use light, airy soil.
- Add perlite/vermiculite or diotomaceous earth (DE). **Dont need to dilute. This helps disrupt the food supply.
- Barrierize the soil. Place a piece of cardboard, paper, or cloth over the soil to cover.
- Neem Oil (Can be used to prevent, and as part of an insecticide)
- Media Topping (use sand or similar ingredient on top of soil to prevent larvae from entering).
Stitch, J.C., (Ed., Rosenthal, E.) "Marijuana Garden Saver: Handbook for Healthy Plants," 2008. Quick American. Oakland, Ca. Print.
Terminix, Inc. "Bug Facts". Retrieved March 29th, 2019.