It is late enough that there is no point in spraying.  Not a whole lot of info out there for treating aphids late in the season.  I would say if you were only at 50% dented and had a lot of aphids above the ear, then you might see an effect of spraying. At 50% milkline, yield is virtually made.  Some sprayed around here a couple weeks ago.  Didn't personally spray any but had spots with some heavy pressure.