Single Quaking Aspen Declining: Check for Root Pests or Cytospora Canker

One aspen in a group showing dry branches and leaves could have root-feeding pests (look for tunnels, digging) or Cytospora canker, a common fatal disease.

Diagnostic Steps

1. Inspect base of affected tree for animal damage.
2. Examine bark for sunken, discolored, or broken areas—classic canker symptoms.
3. Compare with healthy neighbors.

Reference

Photos of Cytospora canker: USDA Forest Service

If canker is confirmed, the tree will likely die; remove it to protect others.