I had root aphids. They suck. I tried an Azamax drench twice and it did not work. I ended up using Sevin. It worked quickly. It's nasty stuff though. It is not systemic so it's ok to use in flower as long as you do not get any of it on buds. I would only treat the soil even if you were in veg. It is also not labeled for indoor use, but you can treat outside and bring them in after you treat them. I just sprinkled it on top of the soil and watered it in. They also make a liquid version that may be easier to use. Make sure you wear gloves, mask, and cover your arms when you apply. You do not want to inhale or smoke the stuff. I'm not suggesting that you use it, just saying that it works. Do your own research and make sure you use it properly, if you do.

Another option is using a trap plant. Supposedly root aphids love nasturtiums. You can sprout some seeds and threat them with imidacloprid (bayer tree & shrub) then put them in your grow room. I have heard that the imidacloprid stays in the plants for a really long time and that it should not be used even in veg. BUT, if you use a trap plant you do not have to worry about that. Make sure you sprout your own nasturtiums though. You wouldn't want to introduce any other insects from a nursery plant.

I thought I had fungus gnats for the longest time and did nothing until the problem was out of control. Sevin killed them fast, but I started getting weird dead splotches on my leaves, then the leaves would die. I believe this is from the root damage. I also started getting premature yellowing in two other plants that I also believe is from the root damage. It still looks like I will get an OK harvest, but definitely not as good as it could have been.