There seems to be some confusion around here between Root Aphids and more common Aphids that attack the foliage, and secrete "honeydew" that ants love. -granger
Well if you look at the pic of pest in question, the real confusion is between RA's and soil mites. The pic is a mite, a harmless soil mite.
But yeah, being that I am not a RA expert, some clarification as to what species of aphids are "herded" by ants is in order. Makes sense that the RA's I've seen aren't the herded type.