Wooly aphids or root aphids both respond to alcohol. I regularly use a 50/50 solution as a root wash when transplanting and as a soil drench on established plants. Plants don’t seem to mind the alcohol treatment.
I usually spray the bare roots of divisions and transplants with alcohol, as root aphids are my main pest problem. Some Primula seem to be able to deal with them better than others. The only way I can keep on top of the problem is regular repotting and alcohol. If a variety keeps showing up with root aphids, it is likely to find itself becoming compost!