Root Aphids are probably one of the worst pests you can get in your plants. You want to kill them and not mess around. If you use a bunch of chemicals you can build up their resistance and make them stronger each generation. The chemical "Imidacloprid" is an aphid killer, and this chemical is used in many expensive pesticides in high% ratings. you can get the same chemical for about $12 in several Bayer products. I use Bayer Fruit & Vegetable for Root Aphids. 2ml per liter and drench the roots. i do 3 applications spaced apart by 5 days between each application. It saved my garden and i've never seen them come back. and i've seen it save dozens of other gardens..