Many leaves with necrotic areas due to Venturia infection.
Jay W. Pscheidt.
Shoot blight due to Pseudomonas syringae on aspen.
Larry Moore, 1982.
See:
Poplar (Populus spp.) - Leaf and Shoot Blight
Note Venturia macularis (formerly V. tremulae) is found on aspen (P. tremuloides).