TL;DR: Does neem oil ruin edible plants or linger in the plant? It smells like shit!
I'm trying to grow herbs in a south facing window and unfortunately the potting soil I used came with fungus gnat larvae, despite saying "no pests" or similar. I've been using stickies and peroxide solution to try knocking them down and finally tried a spray of neem oil and soap. I'm pretty close to giving up and just buying basil, but figured I'd ask.
TIA.
by MisterSofteePSSD
10 Comments
I have yellow sticky traps all over. I just keep them changed. I can’t get rid of the gnats because they are in the yard and sprinkler system and rain drains here in Arizona and they come through the doors even with screens. Old windows and doors. Old patios. Old drains. Oh well. I’ve repotted and changed soil and added grit and covered the soil. Oh well.
Diatomaceous earth works every time. It’s white powder made of crushed seashells that shreds them all up. Mix it generously into the top couple inches of soil. It’s okay if there’s extra, plants like it.
This works every time without fail.
Try BTI, you can buy it as powder or as mosquito dunks
You need beneficial nematodes, only thing that worked for me!
Look up beneficial nematodes for fungus gnat larva control in the soil.
[This stuff,](https://www.organicbti.com/product-page/gnatrol-bti-omri-organic-fungus-gnat-larvicide?srsltid=AfmBOoqm_Rv7TerTnq2P4MeOW0A4HUkf3d2dertm654QA5WbVPOcQA4k) every time you water. It’s safe for edible plants. I used the full dose for active infestation, and half the amount now for maintenance. I have 100+ plants and I see maybe two gnats a week. I also have carnivorous plants that help out. I have a couple of those blue light traps, but I barely see any gnats on those either. No yellow traps — I hate those damn things.
I don’t know if neem oil is okay with edible plants. But when using neem oil you have to dilute it with water and actually water the dirt. Spraying on top isn’t enough because it won’t reach everywhere. I’ve used it for fungus gnats and it worked wonderfully. You use it for watering a few times. It dies work.
Peroxide solution matters on the ratio and waiting for the soil to be dry before you pour it through, or else you’d need to do a little bit of an actual soak in a peroxide solution bath.
Also you’ll want to swap as much of the soil, disinfect the pot, and then repot.
Your soil composition also probably needs review and cleaning the leaf litter from the top of the pot
Lay the glue traps face down on the soil. Change when covered. Keep at it. DTE too.
Change your soil. Then use preventative watering measures.
I water with this:
1 gallon water
1 cup neem oil
1/2 cup peppermint castile soap
1/4 cup isopropyl alcohol