Aspen Leaf Blisters and Black Spots: Yellow Leaf Blister Disease

3-year-old aspens (3 feet apart) show hollow blister-like bumps on 90% of leaves (worse lower down). Second tree has black leaf spots. Previous aphid infestation controlled with ladybugs.

Primary Diagnosis: Yellow Leaf Blister (Taphrina)

Blisters match Taphrina fungus—favored by cool, wet springs. Mostly aesthetic; doesn't threaten tree health. Spraying now ineffective; treatment must start pre-budbreak next spring with Daconil (2-3 applications). Rake/destroy fallen leaves before spring.

Black Spots: Likely Environmental

Not a true disease. Ensure adequate water during hot/dry periods for vigor.