This looks like it might be a hickory or an ash tree. We will need additional photos to identify the species—the starting point to determine what might be ailing it. Would you be able to send us photos of the branches? We would need to see the leaf arrangement and whether they are opposite or alternate along the stems. Photos of the whole tree and the base of the tree would help too.

Also, can you tell us how much of the tree is affected by symptoms? How long ago was it planted? Have any changes occurred around the tree's root area recently (e.g., construction activity, compaction)? Is there any visible damage to the trunk?

Christa