Bugs on Docken roots?

[kit-e-kate]

Hi all, I was just out doing some weeding and I noticed that all the docken roots I pulled up had a cluster of tiny dusty grey-black aphid-looking bugs on them. They were not on any other plant or root. Does anyone know what they might be? Obviously if its some kind of docken destroying beast then i'm not too bothered about getting rid of them, but if they are something awful that's going to spread to other plants then i'd need to take action!

Alll thoughts gratefully received!

[Odsox]

Sounds like a root aphid, especially if there is a white powder on the roots as well.
I had (probably still have) an infestation of Lettuce root aphid this year which severely affects the plants to the point where they just collapse and wilt. Don't think it's the same aphid though as apparently this one only affects Poplar trees and Lettuce would you believe.
I have also seen root aphids on buttercup this year too.

Mr Google says your aphids are probably (sweet)corn aphids, if that's what they are.