Alcohol and the bti are the best defenses. I had an infestation directly in my root system on some bubble bucket dwc plants, they were eating the roots and multiplying like crazy. I used neem and it had little effect, azatrol worked better it slowed their breeding and movement considerably, but when I started spraying alcohol on the roots and the tops on my soil on my soil plants it devastated the gnat larvae. The plants showed no signs of trouble from the direct alcohol on the roots but it killed the larvae on contact. I tried peroxide it does nothing at all to the gnats or larvae. Also believe it or not straight chlorine bleach didnt kill several that I put directly in a cup of it, they just crawled away. I also mixed some bti/water up.and poured it on everything, it has prevented reinfestation. Bti works very well, I put it in my livestock drinking water reservoir (per instructions on the package, 100% safe for mammal consumption) and it totally prevents the larvae stage of mosquitos also. Bti/azatrol/ISO alcohol are life savers.
Last edited by upinthemguts; 09-05-2012 at 05:53 PM. Reason: spelling