Greetings and salutations SKUNK fans. A couple of years ago I did an article regarding fungus gnats. The formatting of it and lack of any photos for some reason, inspired me to do this article. I get a ton of peeps asking me about fungus gnats, crazy concerned their gardens are about to be destroyed by disease and parasites. I always say: Not hardly, heh heh.
It may be hard for you to believe just how beneficial fungus gnats are. While it is true, they can be root hair eaters, carriers of diseases, and other threats to your gardens, this is only true if they have come from a place with those kinds of problems. Born and raised in your own garden, the only threats they can be carrying are threats that were already present in your garden. You savvy? Let’s rock baybee…
Fungus Gnat Lifespan
There are a lot of different kinds of fungus gnats. All are very similar. Infestations come in waves. Each wave lasts about 10 to 14 days. You’ll know that you are doing something right if their numbers decline considerably in about 7 days. Fungus gnat eggs only take like a week or less to hatch into larva with warmth and moisture. As larva, in the top couple inches or so of your containers’ soil, they spend about 2 weeks. Then, another week or so, changing as pupae, from larva into fly, and boom! Buggin’-time.
How You Grow Matters
Fungus gnats, in their larval state, are problematic in soilless gardens. They will eat the tiniest of living root hairs. This is due to the fact that in a soilless environment, there’s nothing else for them to eat. In a living organic soil, there is mega food for them under the right conditions. I have seen small plants in small containers with living soil overrun by larva. Didn’t hurt the plants one bit. Small plants I have seen in rock wool and vermiculite that were infested, suffered big issues.
Beyond the fact that they are buggin’ in their flying form when there’s a lot of them. Fungus gnats can cause one other problem that sucks HUGE! Getting stuck all over your gooey buds! Arrrrrg! ☹ Gnats can ride along in bags of bark mulch, manures, and some soil mixes—cheaper ones.
While root hairs can be on their menu, they far prefer compost, compost fungi, and basically in super healthy organic living soil, they have a smorgasbord of food they like much better. Making sure your garden has adequate air movement, especially down low, is also uber important!
Fungus Gnats (Especially the Larval Form) Are Good-Guys in Living Soil
Yup. I wrote that, and I meant it. Especially in their larval form, fungus gnats do a ton of good in containers; If, you are using living soil. First and foremost, aeration baybee. They are tunneling everywhere like mini-Sandworms (from the movie Dune) leaving aerated micro-tunnels behind. There are always one or three fungus gnats buzzing around in my gardens. Healthy sign, and barely noticeable.
Okay. Here comes the real deal I especially love. The larva transport bacteria all around in the highly aerated layer of your soil. Why you ask, does that matter so much? Fungi can haul ass as far as movement through your soil. Finding food. Within a couple of weeks, they can easily have moved throughout any size container. Bacteria only spread two ways. By colonization expansion—super slow. But their primary way is hitchhiking. The fungus gnat larva are just big “busses” driving around spreading the (bacterial) love. FYI – cannabis thrives best in bacterial dominant soil types.
Ways to Deal
What you are really after here, is an end to it all within 10 days. That will not happen if something about your growing environment favors fungus gnats. It can be sneaky. You need to pay attention to specific water needs—on a per plant basis. Some plants go through more water than others. Overwatering a single plant can catalyze another whole invasion cycle.
For SURE get some sticky fly traps (see photo). Put them up as fast as you can. This will really help to throw a wrench into the breeding cycle, the buggin’, and the flower sticking problems. This will help a great deal. Get more than you need so you can replace them if they fill up quickly. Depending on the number of them you are dealing with, you may need to replace the sticky traps a couple times each during the 10 days.
Dangle the traps all over where they fly. Be careful of placement. Trust me, you don’t want your hair, or buds, coming into contact with these sticky nightmares. Use gloves when placing or removing sticky paper traps. When purchasing these sticky traps, make sure they have zero aromas added. Obviously no insecticides either.
BT (Bacillus thuringiensis) works well. Some people say only one strain of BT works on the fungus gnat larva. In my years, I have seen both strains of BT (apparently) work fine. But you don’t need to care about any of that. You only need care about what brought them. And what is keeping them around. This will end them within 10 days. This doesn’t need to be a “war” on them. Just let them burn themselves out. They only live 7 days. Everything is going to be fine 😊
Rev’s Best Tips for Fungus Gnats
My ultimate advice for a fungus gnat invasion, is to ride it out for a week or ten days. Use sticky traps. If they persist after ten days, you need to review your growing habits. Specifically, your watering habits, humidity, air movement, and air exchange. Modify your air movement, to be better; now.
With good air movement and lower humidity levels (like in the 40% to 60% range) you will effectively end the cycle of flying buggers. Overwatering is another biggie. Bottom watering is only somewhat effective, the gnats will just set up shop where the drain holes are and remain in some number. Let your plants dry out well between watering times.
They can be crazy bothersome. I know. I have had hundreds of gnat invasions myself, I’m sure. The real problem happens when you are a home grower, and the gnats can access your house when you access your grow room. I have had to put coasters on top of my morning coffee to keep the gnats out; they really dig coffee. Pretty bad when you can’t set down a drink for 5 minutes in your house without finding a dead fungus gnat in it.
Okay, See You…
I hope most of all today I have calmed you down regarding fungus gnats. They suck for sure! But it’s really just sucky to you, heh heh. I mean if you are growing in living soil with plenty of decomposing organic matter present. I want to also mention DE (diatomaceous earth) here. If you have worms living in your containers, like me. Do Not Use DE! Also, DE can take your soil’s pH up quite handily, which can be risky. Way riskier than just letting them burn out.
Here’s another article by me if ya wanna check it out: Using Bone Meal. Lastly, before I go, I just want to say, a few extra bucks spent on soil, mulches, compost, or manure, will be worth it. Soil mixes that have a lot of peat moss in them are particularly fungus gnat friendly. Mushroom compost needs to be of high quality especially, if you use that.
Dial in watering stuff, air movement/circulation, and your problems will end in a week; most likely. If they persist just look deeper, and you’ll figure out what is keeping them extra happy. Then end that! Alrightythen earthlings, I’m outty for now, but I’ll see ya back here at SKUNK next week.
I'm The Rev, and I have been with SKUNK for about a decade now. I hail from Southern California, spent mucho time in Northern California, and now reside in Southern Oregon; always coastal. I am an all natural style cannabis grower and I have written a couple books on the subject - check out True Living Organics 2nd Edition on Amazon - I have been growing for over 45 years, and I have been breeding cannabis for over 30 years. Check out kingdomorganicseeds.com to see some exotic selections. Growing connoisseur cannabis is what I teach mostly, growing it in living soil without using liquid organic nutrients to feed the plant. I am also a highly skilled synthetics grower, hydroponics, aeroponics, DWC/SWC/NFT, Ebb and Flow, and soilless, but I cringe when smoking synthetic grown herbs, so for the last 15 years or so I preach the artisan style of all natural growing, specializing in container growing. Cheers and welcome aboard.