I have also ordered gnatrol, off Ebay. I feel that this will work, but the plants must be isolated as much as possible, to avoid gnats coming from other parts of the house to re-infest. I am going to get zip-able covers for my shelving.
I was also advised by Runningfox on the LA that SCAN MASK nematodes will work on an active infestation. I think this is more difficult because the nematodes are expensive and have a short shelf life. But I might do it if I have to.
Last year I had a terrible time with the gnats.
I tried Mosquito Bits, used them consistently, and they did not work, though they supposedly contain BTI. I tried that glass-based sharp sand to top off the pots, it did not work and cut up my hands. I ended up repotting all the ones I used it on. I tried sprays, which did not work. I finally ended up dusting regularly with diatomaceous earth, which worked somewhat, but coated everything in the room with white, gritty dust.
