we planted a silver maple in our yard 2 summers ago. this spring it got all it's buds and has grown twice it's normal size, but we noticed the top of the tree has died about 4ft. of it and the bottom is still alive. could someone have sprayed some kind of killer like round up and it has affected the tree? also we had 4 big bare spots on our grass that has died also for no apparent reason. any idea's?