How to contain/kill Fungus Gnats in coco or soil (organic methods only)

Thegermling

Well-Known Member
This thread was created from scattered pieces of information across Rollitup and the internet in hopes of having it in one condensed form for noobs and the experienced growers. This thread is for anyone interested in dealing with the dreaded fungus gnat 100% "organically."
The Fungus Gnats that cannibis growers deal with are from the Mycetophilidae and Sciaridae families (usually). The adults are 2-3mm long. They don't bite or sting. Do not confuse them with root aphids! Root aphids have a rounder broader body, and are more attracted to your grow lights whereas fungus gnats have a long, very thing body and are attracted to moist mediums. The adult fungus gnat itself does not do any damage to the cannabis plant. The fungus gnats mate and the females lay their eggs in the top inch or two of the medium (usually). It is not unusual but they can make their way from the bottom holes and sides from certain containers and lay eggs there too. The larvae are the real cause for concern. The fungus gnat larvae feed on fungi, decaying plant material, organic plant material, algae, and perhaps the most concern for any grower cannibis or not, the plants roots! This creates wounds that open up the path for infections like pythium, fusarium, and phytophthora thats to name a few. Plants stop growing, discolor, wilt, water and nutrient uptake will slow. Everest Fernandez and Wikipedia.
Chemical pesticides (Avid,floramite,etc.) should not be used on cannabis plants whether they be for medicinal purposes or recreational purposes (in states that it is legal) whatever the case may be. These types of pesticides are systemic; what this means is even if you spray said insecticides on plants in the vegetative stage it will always be resident in the plant, it is in the system of the plant. Two months later, when the final flower is produced, that insecticide (Avid, Floramite, etc.) will still be in there. You will be infecting your plant with a chemical that is completely undesirable. Not just that but you smoke the plant and ingest those chemicals. Growing your greens.
Maintaining a clean environment isn't always the best thing for preventing fungus gnats. When getting plants whether it be clones or whatever, ALWAYS ASSUME it has fungus gnats or any pest for the sake of having a "safe" grow area. No exceptions, It shouldn't matter if it is a plant from one of the most top notch grow ops/dispensaries in the country or in the world. If you grow your own from seed, then in this case, having a "safe" grow area is key. Fungus gnats can catch a ride on your clothes, they can be in plants obtained by friends, dispensaries, etc., they can get into your grow op through cracks in doors, walls, and they can be present in purchased mediums (depending on the source of course). Also, inspect purchased containers too.
When you do recieve a plant from an outside source and you want to introduce it into your grow area, ALWAYS do a foliar spray and medium drench to contain/kill any pests "present" on the plant.
Now I will list some organic products that will kill most pests, some of these products are of course for the fungus nats, for the sake of this thread.
(ALWAYS CHECK EXPIRATION DATES. If the product does not work , it may be because it is expired/ineffective.)

  • Azamaz (medium drench until gone/follow instructions, can be used in conjunction with other methods, can mix with nutrients,) GH (General Hydroponics)
  • Azatrol ( medium drench until gone/follow instructions,can be used in conjunction with other methods, can mix with nutrients )(Gordon's)
  • Azasol (medium drench util gone/follow instructions, IT IS BETTER TO USE AS A STANDALONE)(Arbor Jet)
  • Microbe-LiftBMC (Better than mosquito dunks/bits etc. From my research those products "mostly" contain just BT.) (Bacillus thuringiensis this is important sub-species israelensis this targets the fungus gnat larvae. Apply as a medium drench, 6 drops in a gallon for 2 weeks then 2 drops after, every day until harvest. Won't affect PH. Compatible with all nutrients. DO NOT USE WITH ANYTHING THAT KILLS LIVING MATERIAL I.E., h202/Hydrogen Peroxide. Dude Grows.) (Ecological Labs)
  • goGnats (medium drench until gone/follow instructions, can be mixed with nutrients. Can be used in conjunction with other methods ) (Earth Juice)
  • Nematodes (Steinernema Feltiae (SF). The more/concentration the better! Store in fridge. Apply in dechlorinated, aerated water. They take up to 24-48 hours to migrate into fungus gnat larvae. Apply evenly, PH 5.5-6.5. School of hard nugs.) (DO NOT MIX WITH FERTILIZERS OR CHEMICALS, allow one week between application of fertilizer or chemicals and the application of predatory nematode product. Yardener) (Buy nematodes at BIOLOGIC)
  • Stratiolaelaps Scimitus ( A predatory mite.) (Bioline: AgroSciences)
  • Yellow or Blue sticky traps (or any other organic modified version of this like Gnatstix etc) (This only helps in preventing adult gnats from mating, place them horizontally and/or vertically, horizontal is better, place them on the medium so they can get trapped.Can be used in conjunction with other methods)
  • H202/Hydrogen peroxide (Mix one part 3% hydrogen peroxide with four parts water and water. DO NOT USE WITH ANYTHING THAT KILLS LIVING MATERIAL!)
  • Food grade Diatomaceous Earth (DE) (In my research this does not work when wet.)
  • Big Time Exterminator ( Medium drench, CANNOT BE MIXED WITH OTHER NUTRIENTS, USE AS A STANDALONE) ( Apogee Garden Products)
  • Gnatnix ( works dry and wet. Can be used in conjunction with other methods.)(Growstone)
  • Sand (sterile/or playground sand, like gnatnix and DE, this can mix with your medium after awhile which can be a pain.)
  • Powdered Cinnamon (true ceylon cinnamon or cinnamomum verum. This kills the fungus that the larvae feed on. DO NOT USE WITH ANYTHING THAT KILLS LIVING MATERIAL.
  • SM-90 (The most controversial item on this list, it is organic, the owner (Kelly) said that the sm-90 formula "selectively" kills non-benificial microbes, while (many) others have said that this product acts like H202/Hdrogen peroxide, basically a medium drench/ follow instructions. Can be used in conjunction with other methods. USE AT OWN RISK! (Nutrilife)
  • Gnatrol (Better than mosquito dunks/bits etc. From my research those products "mostly" contain just BT.) ( This contains BTi too (same as Microbe-LiftBMC, there is some variation. DO NOT MIX WITH FERTILIZERS OR FUNGICIDES CONTAINING COPPER OR CHLORINE. Their label says chlorine in potable water should not present a problem.) (VALENT)
  • APPLE CIDER VINEGAR and SOAP trap (Fungus gnats are attracted to vinegar, wine works too. Fill a baby food jar up half way with the vinegar and add two drops of dish soap, the vinegar attracts the adult fungus gnats and once they are on the vinegar the soap makes it so they cant fly out. This is only good for not letting the adult gnats reproduce. It didnt work for me, might give it a second try.)
  • Potato slices (Cut raw potatoes into 1 inch x 1 inch x 1/4 inch pieces, place the slices next to each other on the surface of your medium. Leave for 4 hours then check underneath, scoop up and throw away the larvae in the toilet.)
  • Let the top of growing medium dry out (Top inch or two. DO NOT LET COCO DRY, salt based fertilizers that dry will cut up roots!)
  • Irrigate pots from below ( Best with fabric pots)
  • Cover pots with panty hose ( this works best with airpots with many holes, try it on fabric pots.)
  • Cover tops of pots with pandafilm ( This prevents algae (which fungus gnat larvae feed on) from growing and acts as a physical barrier against adult gnats, any thing that reflects light is a plus!)
  • Neem cake or seed meal ( As a preventative measure/and treatment, use in conjunction with other methods. (Down To Earth brand and other reliable source)
  • Neem Oil ( Medium drench, cold pressed neem oil. Can be mixed with nutes and other methods. (Super Clean Neem or other reliable source.)
  • Pyrethrum/Pyrethrins and cinerins NOT PERMETHRIN, which is synthetic. ( A medium drench, can be used in conjunction with other methods such as neem oil, and insecticidal soap. Better not to combine with nutrients. ALERT!, even though organic, pyrethrins are a neurotoxin. USE AT OWN RISK!)
  • Tabacco ( A medium drench will be effective, I DO NOT RECOMMEND THIS METHOD, THE WRONG RECIPE CAN DAMAGE PLANTS. USE AT OWN RISK!)
  • Insecticidal soap ( There are several soaps out there that can be used as a medium drench and/or spray the top surface of soil to keep adults fungus gnats from burrowing in and laying there eggs. (Dr.Bronner's)
 

Thegermling

Well-Known Member
DONT TRY JUST ONE OF THESE METHODS, mix them up (the ones that can be mixed up). I have heard of some fungus gnats developing immunities against some of these methods. For example, one grower used Gnatnix and he said the fungus gnats werent even fazed.

I will update this thread whenever there are new methods of pest controls for fungus gnats (organic of course). If any of you, my fellow growers, have any methods I may have missed, feel free to reply. We should all have the mindstate of "sharing knowledge", if I incorrectly stated anything wrong about the products above, feel free to reply so we can have the "right" information on here. Again, this was all gathered from multiple threads and posts scattered from rollitup, youtube, essentially the internet. Good luck to you all, grow consciously!
 

med123

Well-Known Member
Hypoaspis miles (predatory mite)

Targets the eggs, larvae and pupae of Fungus gnats, preferring smaller larvae. Also targets other soil-living insects like thrips pupae, collembola and nematodes. This is all I use and have great success.
 

Thegermling

Well-Known Member
Nice. I just added some gnatnix to my coco, have only seen a couple of flying gnats now. I added BTi, still have the sticky traps out. I might order the nematodes or the predatory mites if they arent gone by next week. Thats when my auto enters the flowering stage.
 

Budbreath

Well-Known Member
Somebody help me out. I have Monterey but. Its liquid. Can I mix it up and water it in the coco?
 
I used hydrogen peroxide when I had gnats. Since the root of the problem is overwatering, the hydrogen peroxide will kill off your beginning stages of root rot that's feeding the gnats plus it'll oxygenate your root zone and aerate your soil so it'll dry quickly. The problem is that it sanitizes beneficials like mycorizzae as well. From there you really need to get back on track and only water when you can lift the pot easily and your leaves droop from the loss of osmotic pressure in your medium.
 
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