Question
I read your description of the deceased weeping elm. I am now convinced that my weeping elm has had European Elm Scale for a number of years and now there seems to be some kind of little flying insect with transparent wings nesting in curled up leaves like a cocoon with hundreds of off springs in every one of these cocoons. Is there anything other than Imidacloprid (which seems toxic...the tree is 5 feet from my water well)that I could use...something safer?

Answer
You said that the tree had scales does it still have them?? The insect you describe sounds like a lacewing--a predator of scales. IF their population has built up then they will take care of the scales and you will not need to apply insecticides. IF the scales are still active you can spray the tree with an insecticide called Orthene. The tree maybe too tall to spray that is why the soil applied insecticide is recommended. But in your case I would stay away from the soil applied--it probably will not get into the water well but being this close I would spray instead of the soil applied. First see if the lacewings will control the population of scales and if not use the orthene. http://www.entomology.umn.edu/cues/Web/126EuropeanElmScale.pdf