Just to add something about neem oil...neem is a preventative measure. Generally, you should use neem when you have a threat but not a full blown invasion. Neem oil acts as an inhibitor in the sense that it stops the insects' reproductive cycle, thus causing them to eat less and not breed anymore. It does not kill the insect per se, just stops the insect from breeding and then also from eating since they have, at this point, nothing to live for. So, if you see a little problem beginning to develop, then get a little neem oil, some organic, non-scented dish soap, water and a spray bottle. Mix it up ( i use a drop of dish soap, 1 teaspoon of neem and 1 liter of water), spray it on and wait. Sometimes, the problem is deeper that you think, like in the soil and not just on the surface. If this is the case, I guess you'll have to go the insecticide route (i did on my first grow). The neem also works well when used from the beginning of the grow. Obviously, not when the little girl is one inch tall, but once a couple of nodes have started. It really stops a lot of aphids, spider mites and gnats. But be warned, it doesn't exactly smell like roses...more like a 12 hour train ride in India.