substitute for FE (fish emulsion) needed

Hello, I am just getting started with trying to incorporate permaculture in my yard, but I have a question regarding patio plants that I currently move in the house in the winter and move out for the summers. I have 3 dwarf citrus trees, that got covered with some kind of scale (insect) and was just killing them. Everything I read recommended spraying with fish emulsion. I did, and it seems to have worked well, but I wanted to know for the future what the best vegan treatment option would be for controlling pests on citrus. I also wondered if there was a recommended treatment for aphids, because we have a plum tree that is loaded with them right now and I need to treat it somehow. (aphids are really bad in my suburban neighborhood) We are in zone 6 south central PA. Thank you for any suggestions!

Hot pepper wax, and go to a garden center and pick up some predatory insect eggs and sacs. Ladybugs, and lacewing is good for scale. Dabbing alcohol swabs on the young, unarmored scale will kill them quicker than hand removal.

Thank you for the suggestions, I had tried neem oil, but I didn't realize hot pepper would work for insect pests, I thought it was only for "chewing" type critters! And I never even thought about plain rubbing alcohol. Thanks again!