I have a number of Austrees (Similar to willows) that are being over-run with a small aphid like bug that is dark red in color. They swarm around and up and down branches apparently feeding on the tree sap. After awhile the leaves fall from the branch and many later are dead. They are multiplying and have now spread to several trees. If you smash them they leave a red stain that looks like wine. Can anyone help me identify and suggest how to deal with these pests. I am worried that they will end up killing all of my trees which I planted 14 years ago and are over 30 feet tall. I usually try to go organic but would be willing to do whatever is necessary to save my trees. Thanks for your input.