What to do about plum aphid leaf curl?
My Mom's house has some fruit trees planted by the previous owner, one is a pretty big Santa Rosa plum and the first year it had one branch with lots of curly leaves. The next year it had even more curly leaves, I went to my favorite nursery to ask what to do and they said that it's plum aphids and the best thing is to just leave them alone and let the natural predators eat them. Two years later the Santa Rosa is heavily affected and I just noticed aphids on my new Elephant Heart plum as well, so I'm tired of waiting for natural predation to take effect and I started looking into other methods of control.
Everything I've found is geared towards commercial crops, and the pesticide info is pretty technical and intimidating. Any suggestions about backyard orchard techniques for plum aphid management? I would rather not use really nasty chemicals, but I have a sprayer and will break it out once the trees have gone dormant.
Thanks in advance!