Last June my elm tree started dying. I noticed a lot of scales on the branches and took photos of them (attached). The entire tree is now dead, from Dutch Elm's diseas, and I am having it removed. Only one of three tree companies I spoke with, Vineland Tree Care, acknowledged that the scales could have existed. Are elm scales rare in the area? How do they spread? How can I prevent scales in the future? Thank you for your time, Jennifer