I am having a problem with root gnats (root aphids). I have tried cinnamon, garlic, cayenne pepper, and it slowed them down a bit. 4 days ago, I treated with neem oil, 1 tablespoon more or less, with a few drops of dish soap in 2 liters of water. I am using it as a soil drench only. I did my second treatment yesterday, and will follow up every 3 days till those lil fckers are gone. I am noticing that maybe 75 to 80% of them are gone now, and the flyers are slow and not doing so hot. I do not know about the neem staying in the plant. I am 4 to 5 weeks from harvest, so I am going to stop the neem as soon as I feel comfortable that my pests are gone. Then I will flush the hell out of it.