Fungus gnats, advice?


From a fellow grower:

Currently growing indoors with soil. Currently have two females in flower (two weeks). And some seedlings in veg.
My biggest problem have been fungus gnats!! That wiped me out once. I cleaned and cleaned and started again.
Got them again . I’ve hit them with BT dunks , that wasn’t working so I did 1 to 4 parts H2O2. And some yellow sticky paper .
Now I think my PH is messed up from the H2O2 from the looks of my seedlings…
But I’m still seeing a gnat from time to time and I’m worried about infection of them again !
I’m growing in an old BC Bloom Box. I’m not using the hydro . I took the pumps out and growing in soil .
From now on I’m stearlizing my soil too in oven at 180*F for 30 mins.
So, my biggest problem is fungus gnats. Do you see anything that I may need to do? Or do you feel I’ve got it covered?


start with this dust your soil plant top to bottom don’t stop there dust your whole grow space if ph is becoming an issue which direction up? down? you can simply adjust your water to compensate make it slightly more or less acidic to et your run off to the right lvl. After several waters it will be back to where you want
Gnat nix is also recommended but slightly more expensive


Keeping the soil too wet for too long is often the biggest contributor to fungus gnat problems, be very careful to not be over watering. Dusting the surface of the soil regularly with food grade DE does help a lot, and also with other critters, such as spider mites, that lay their eggs in the soil.

Over watering, in and of itself can also mess up your soil’s pH, often to the acidic as it also contributes to anaerobic bacteria and other decomposition that tend to turn things towards the acidic.