Fungus gnats. Let me tell you about fungus gnats. I’ve lost many plants due to fungus gnats. First, Don’t panic! Second, take those domes off your plants, please.
Fungus gnats are little gnats that lay eggs in the soil. The larva like to eat the small hairs on the roots which will kill a young plant. Don’t throw your dirt out. It’s not your dirt’s fault. They get in everything year round no matter what you do.
Here’s how I solved my fungu gnat problem. First, I made a small cabinet with a compact florescent for starting plants. Then I put this cabinet in a different house, far far away from my big grow.
Then I make my own starting soil. For starting soil, I use left over potting soil that I used for the big plants. But here’s what I do with it first. I put my left over dirt in a big black trash bag and set it on the back porch in the sun for a couple months. This kills the fungus gnats and any other nasty things that might be lurking in the dirt.
When the dirt is ready I put it in small coffee cup size pots and put the pots in the cabinet. I water them for a couple days until the dirt has acclimated to the cabinet, then I plant my seeds in the pots.
When the plants get about 3 inches tall and the roots are starting to poke out the bottom, I transplant them into 3 gallon bags and put them in the big room where they grow into big happy plants.
I also hang a sticky trap in the small cabinet just incase one of them little buggers manages to sneak in. Like I said, they are every where.
Once the roots of the plants are a few inches deep you don’t have to worry about the gnats anymore. Fungus gnats’ larva only live in the top inch of the soil. But you’ll still see them buzzing around so put up a couple sticky traps in your grow anyway.
So you can’t wait a couple months for your starting soil to cook in the sun? No problem. Put your starting soil in a baking sheet, and put it in the oven at 200° F for ten minutes. (100° C)
But your plants are falling over and you need to get rid of the gnats right now, ASAP? Neem oil. The stuff is awesome. Not only does it kill fungus gnats, it kills mold and mildew. Neem oil is also 100% organic. Follow the directions on the bottle. I think it’s about a teaspoon or two per gallon of water. Spray it on everything. Then pour some of the water on your plants too. Do this every other day for a few days.
This is why I advise against direct seeding seeds in your final pot. Yup. I learned the hard way.