We have a large sycamore tree in our front yard. The leaves have recently started to turn brown and fall. There are some leaves on the tree that are still green, but there are many that are falling. We raked them up yesterday since the front yard was covered and now this morning it is almost covered again. I have read that it could be a leaf blight?? Is there anything that we can do for this?? If so, how can we solve this problem??