In the last couple years,there were Curly Leaf Plum Aphids attacking certain grafts on a Flavor Supreme,particularly,Purple Heart Plum and Santa Rosa,while leaving everything else alone.
I sprayed a few times with a soapy mixture,but the leaves were really curled.The grafts were young and didn't have fruit yet,so no biggie.
This time,just up to seeing a little color in the flower buds,I sprayed the whole tree with a quart of water,mixed with about a tablespoon of these ingredients:some kind of natural dish soap,baking soda,Soybean oil and Neem oil.There were no Aphids this Spring like before.Only now,a little shoot had some,and were promptly squished.
I have a potted Nadia Plum in a greenhouse and some ants lead me to a few leaves infected with the non curly type.They had to be sprayed twice and after that,the tree was rinsed with water to remove any others and the residue. Brady