I bought a house from an older couple recently and due to being elderly, the upkeep on the property wasn't done. I had what I believed a very nice and healthy wild plum tree. Recently it has been infested, heavily, with aphids. I have tried hitting them with water as suggested in another thread as well as neem oil and insecticidal soap - all which I have been lead to believe would dent the infestation and not do heavy environmental damage. (They haven't.) None have worked. Spraying with water seems only to get the leaves wet. The aphids seem to be very sticky and the only way which they come off is by rubbing the stems. I'd like to know how to control the aphids directly and I'd like to know what I can do nutrient wise/soil wise/otherwise for the health of the plum tree. (This is why I posted here and not right in the bug help forum.) I've attached some pictures that hopefully will help. Thank you very much. :) Edit: For the spraying, I used my hose attachments "flat" setting. We're on well water and the softener is a bit wonky so the water is very salty. I try not to water any plant with the water, opting for the water from my fish tank. And any tips for prevention for next year would be muchly appreciated. Thanks again!