The Dude Grows Show

The Fungus Gnats Must DIE

Long story short…. I’ve got fungus gnats thriving in my hydro closet. It’s a drip system that circulates 5 times a day using rockwool and clay pebbles. I’ve tried a hydrogen peroxide dilution dunk that helped a little, mosquito dunks in res, sticky traps, and some bt spray. All have helped, nothing has worked. I’ve seen products like T-Drops, Gnatrol, mosquito bits. Can anyone help? What can I do?


11 responses to “The Fungus Gnats Must DIE”

  1. J Mystro Avatar

    What are your water temps? If you’re not around 68 F, I highly suggest you get temps down to around there. In an always wet hydro system fungus gnats can get out of control. They LOVE a warm environment. Finding a way to seal up their access to the rockwool/clay pellets is your best bet to keep them out. Lots of options to try to control them after the fact, but you need to break their life cycle to end their existence in your grow. This involves killing their eggs and preventing them from laying more. If you continue to give them access to your roots, they will never get under control.

    1. Big Planet Avatar

      Water temps luckily stay at 65-68 year round. I stupidly brought the gnats into my grow, many years with no problem at all. Thanks for the tip. I will definitely be monitoring more closely in the future.

  2. NayHay Avatar

    Use a tiny pinch with every watering for a couple months until 100% eliminated.

    1. Big Planet Avatar

      Thanks for the recommendation. I’ve seen this product but have not found a small enough size to purchase. Most of them cost around 500$. I guess I should look a little harder.

  3. Krommm Avatar

    During an outbreak, I tried Microbe-Lift BMC. I added 1 drop per gallon to each of my Octopots’ reservoirs (combined with yellow sticky traps to take care of the flyers). It took 2-3 weeks of use to break their lifecycle; kills the larva. Followed up with a biweekly preventative dose and they never came back. Very effective, safe and relatively cheap.

    1. Big Planet Avatar

      I will definitely be looking into Microbe lift. Doesn’t appear to be expensive. If it’s safe and work well, this may be the way to go. Thanks for the suggestion

  4. Evil Coach Steve Avatar

    that’s a pretty empty sticky trap compared to what I get in the summer. They end up, seemingly, breeding in my pots. I’m talking hundreds or more. In the end, all they did was annoy me by being there, so consider the cost to eradicate vs the damage they’re doing. For me, in my hydro/coco setup, I just use sticky traps to control the numbers and look forward to winter.

    1. Big Planet Avatar

      Thanks, I definitely will keep going with the sticky traps for a while. The trap in the photo was just placed in the grow. It doesn’t represent the amount of gnats in any way. My main concern is that the roots don’t look as healthy as they did before the gnats. Also while in bloom, they get stuck to the sticky trichomes. More traps couldn’t hurt

    1. Big Planet Avatar

      Thanks!! Excited to check this out

  5. MidMOGrower Avatar

    I had an infestation of gnats, hundreds of hundreds. An OG grower told me how to get rid of them in 2 weeks. And it worked it took me almost 3 weeks till they were gone and never come back.
    Make a 5 gallon tea of 2 cups of Insect Frass, 1 Cup Karanja cake and 1 cup neem cake. Brew for 24 hrs and feed. Do this for once every week till gone.
    Then to keep them gone top dress with neem and Karanja cake.

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