I live in Eugene, near Oakway Park. There is a huge sycamore tree in my back yard. At the end of each branch of normal leaves, there is a small shriveled up leaf covered in white powder. It looks diseased. All the leaves like that are falling prematurely. I was once told that the tree should get more water, but it is so huge, that I don't even see how my occasional watering the surface near the tree will help. It must have very deep roots underground. Is it lack of water that is causing this, or something else? Is there something I could/should do about this? I will include a couple of pictures.