I have a mature Japanese Lilac Tree that for the first time (after a dry winter in Colorado) has edges of some leaves curling and turning brown, not sure if insect or drought related? Thank you!
Japanes Lilac Tree
Certified GKH Gardening Expert
It is difficult to tell from just your description. It could be from dry conditions or more serious diseases such as blight or verticillium wilt.
These links have more information.
You can also talk with your County Extension Office.