There are ants farming black aphids on my borage plants; the infestation is not bad yet, however I can't spray the aphids off of the plants with the hose. I gave them several full blast sprays directly on the underside of the leaves; those suckers cling. I didn't dislodge even ten percent of them. I think the bristles on the borage are protecting them from being sprayed off. Any suggestions as to what to do next? What will get through the borage prickles, kill the aphids, and not harm the plant? I want to get this infestation while it is minor, rather than waiting until there's a population explosion and they spread to other plants.