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Let's Talk Fungus Gnats

With which pest or bug have you had the biggest problem?

  • Ants

    Votes: 0 0.0%
  • Gophers

    Votes: 0 0.0%
  • Leaf Miners

    Votes: 0 0.0%
  • Mites (Spider Mites)

    Votes: 0 0.0%
  • Spiders

    Votes: 0 0.0%
  • Rats

    Votes: 0 0.0%
  • Slugs & Snails

    Votes: 0 0.0%
  • Thrips

    Votes: 0 0.0%

  • Total voters
    12

J Obadiah

Well-Known Member
What to do about Fungus Gnats...

J Obadiah
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:
  • Kingdom: Animalia
  • Phylum: Euarthropoda (Arthropods)
  • Class: Insectia
  • Order: Diptera
  • Family: Sciaridae
*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.

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.
  • Neem Oil
  • Beneficial Bacteria
  • Soap & Water
  • Apple Cider Vinegar + Ceyenne Pepper
  • Dawn + Apple Cider Vinegar + Salt
*Elimination is not Prevention*

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:
  • 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).
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!

Obadiah

☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆

Bibliography​

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.
//www.terminix.com/blog/
 

J Obadiah

Well-Known Member
**Quick Addition!
It wasn't mentioned that one can also simply use Hydrogen Peroxide & Water (H20 +H202) as the larvae will die on contact. It will also kill adults, but it takes a lot.
Spray water/peroxide directly onto the medium and you'll hear it fizz. That's normal. Do this 1 to 2x/day for 1 to 2 weeks as needed with your regular watering regimine.​
*****Never mix Peroxide and Vinegar in the same container, the result is PARACETIC ACID! It will harm you by its vapor, and can eat through mucosal membranes, skin, and even some woods.​
Don't get burned!​
 

PhobosAnomaly

Photo of the Month: Jan 2018
Springtails are the worst. They are invincible, they shrug everything off.
I have fungus gnats from a soil I wanted to try. Thank you Lowes, and MG Performance Organics.
The yellow stickies and bait containers are working so far.
 

J Obadiah

Well-Known Member
Springtails are the worst. They are invincible, they shrug everything off.
I have fungus gnats from a soil I wanted to try. Thank you Lowes, and MG Performance Organics.
The yellow stickies and bait containers are working so far.
You know I swear I was about an inch away from buying those sticker pads the other day at Lowes, but I didn't, and I don't really know why lol. So they're working well then? These new plants I've put down once again have to be dealt with like the previous batch, with an insecticide--organic, of course. I feel like I cant win with the spider mites and the gnats. If I get behind even a few days on a grow and an infestation occurs, its such a doosie to get it treated. Lol
 
Be very choosy about the medium you use. Miracle Grow soils are notorious for Fungus gnats. I also always hang yellow stickies in my grow area. Not only catches the critters but tells me right away if I have a gnat problem. I mix diatomaceous earth in the top 1-2" if I'm experiencing problems.
 

J Obadiah

Well-Known Member
Sand on top of soil or medium and sticky traps will have and impact but the best is drying the medium.
Yeah I've read that you can use sand, but I like to topdress so idk how that would work out. But, the traps might do well in the small space I'm in. I have a real thing about watering only when the plants tell me to. I really like to let the topsoil dry completely out before next watering, but I think the early environment they were in had a big, negative impact.
 

J Obadiah

Well-Known Member
Be very choosy about the medium you use. Miracle Grow soils are notorious for Fungus gnats. I also always hang yellow stickies in my grow area. Not only catches the critters but tells me right away if I have a gnat problem. I mix diatomaceous earth in the top 1-2" if I'm experiencing problems.
I didn't think about using them as indicators like that. Duh. Man. Dummy. I will absolutely never, ever use Miracle Gro products whatsoever. I utilized them my first year growing veggies and I was incredibly disappointed. So I utilize three types: Big rootz, Fox Farms, or Roots Organic. All my girls are in one or a mixture of those 3 soils, mixed with a percentage of coco coir, usually around 30% coco. I think that once i get them consistently dried out and treated with some soap or a neem oil spray or something, I'll be fine.
 

J Obadiah

Well-Known Member
Atlest they dont do to much harm unless they really multiply.
LOL kinda what I've been banking on lately. I just keep them in check with small amounts of H202 directly into the medium and it helps reduce the larvae. I'm on a fixed income, so I can only buy what I need at certain intervals. Hence my timing issues. I prepped well, but Pest management is a big one this year--really the first time for me.
 

carcass

Member of the Month: Aug 2019
I hate if i inhale them
They do love going for the mouth-must be the exhaled c02 or something...
I had a fairly annoying gnat problem-bought some mosquito dunks,dropped one of them in the 5 gallon bucket I use for the plants water-it takes about two weeks worth of watering,but at this time,I'm completely "gnatless"
 

J Obadiah

Well-Known Member
They do love going for the mouth-must be the exhaled c02 or something...
I had a fairly annoying gnat problem-bought some mosquito dunks,dropped one of them in the 5 gallon bucket I use for the plants water-it takes about two weeks worth of watering,but at this time,I'm completely "gnatless"
Nah, they like the moisture around our eyes, mouths, noses. At least that's what some research told me lol. They looooove their moisture.

Really!? Thats interesting. Mosquito dunks? What are they? That sounds closer to what I'd like to do, being organic as can be.
 

carcass

Member of the Month: Aug 2019
They're little 2" "donuts" of a bacteria that's harmless to plants and
humans,but death to soil gnat larvae (and,of course,mosquito larvae)
Lowes has them,a lot of places probably carry them-I think they were around $6

1775546

They only kill larvae,so you'll have to wait for the adults to die off-takes a few weeks,but they will just slowly fade away-keep it in your plant water and they won't come back...
 

J Obadiah

Well-Known Member
They're little 2" "donuts" of a bacteria that's harmless to plants and
humans,but death to soil gnat larvae (and,of course,mosquito larvae)
Lowes has them,a lot of places probably carry them-I think they were around $6

1775546

They only kill larvae,so you'll have to wait for the adults to die off-takes a few weeks,but they will just slowly fade away-keep it in your plant water and they won't come back...
Oh wow thats totally awesome thank you. I never heard of them. So I just put a donut in the water jug I use and it dissolves?
 

carcass

Member of the Month: Aug 2019
Meant to add to my last post-drop one in the water for 24 hours before you water the plants with it,gives the bacteria time to populate the water-I use one per 5 gallons-1 will treat water for about a month.
They don't dissolve,so you may have to deal with little floating "chunks" in the water-I don't even strain them out,just use the water,little chunks and all.
 

GrizzWald

Plant of the Month: June 2016 - Nug of the Month: Aug 2017
Only thing scientifically proven for gnats.. reusable and cheap. Recycled glass... gnats not really a problem to our plants (not talking mass infestation, which shouldn't happen in a controllable indoor grow environment) populations are easily controlled..

IMG_0820.JPG
 

J Obadiah

Well-Known Member
Only thing scientifically proven for gnats.. reusable and cheap. Recycled glass... gnats not really a problem to our plants (not talking mass infestation, which shouldn't happen in a controllable indoor grow environment) populations are easily controlled..

IMG_0820.JPG
Thank You, I appreciate that, Ive never heard of this, either. And since I like topdressing this might be the solution.
:rollit:
 
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