This tree looks very sparse and generally stressed. This doesn't look like a disease issue. I would double check the base of the tree for any mechanical damage, check how deeply the tree is planted, and check for any deep mulching. What are the watering practices for this tree? If it was planted in the past few years, it needs regular water until the roots are incorporated into the surrounding soil, and during periods of drought. I would suggest calling the Master Gardener helpline and troubleshooting what the issue may be: https://www.udel.edu/academics/colleges/canr/cooperative-extension/environmental-stewardship/master-gardeners/garden-helpline/