Oak Leaf Blister on Water Oak: A Common Spring Disease

Oak Leaf Blister on Water Oak: A Common Spring Disease

Brown, blister-like spots on water oak leaves that cause curling and early drop are caused by the fungus Taphrina caerulescens. Infection occurs during cool, wet spring weather as buds break. Water oaks (often called pin oaks) are especially susceptible.

Key Facts

• Leaf spots alone do not kill trees; even severe defoliation is usually followed by a second flush of growth.
• Fungicide treatment is rarely warranted except for high-value specimen trees.
• If treatment is desired, apply chlorothalonil or mancozeb at bud swell and again in 10 days.

Cultural Control

Rake and remove all fallen leaves in autumn to reduce spore carryover. Maintain tree vigor with proper watering and fertilization based on soil test results.