Hi, 

It would be helpful if we could see some photos. Feel free to attach some of the leaves, branches, entire tree and the root area at the base. 

Sometimes branch and leaf die back are due to root issues. 

Is it old? Is it too sunny, too wet or too dry? Is there anything eating the leaves? Was there any herbicide used near by or in the lawn area? 

Photos and some answers on the site conditions could help arrow it down but if it is continually losing leaf and canopy health every year there may not be a cure for the problem. 

Emily

Thank you for the photo but unfortunately some of the details are hard to see. Could you take photo from another directions or that has better lighting? 

If you happened to answer the questions from the original response, we didn't receive them. For us to provide accurate guidance, we would need to know some further information: 

How old is it? Is it too sunny/shaded, too wet or too dry? Is there anything eating the leaves? Was there any herbicide used near by or in the lawn area?

When you send additional photos, if you could provide one of the trunk and base of the tree where it meets the ground, that would be helpful as well. 

Emily