Oak Leaf Blister

Sherrie Smith and Jason Pavel

Plant Health Clinic Disease Note Issue 15

Oak Leaf Blister - Taphrina caerulescens. Photo by Sherrie Smith, University of Arkansas System Division of Agriculture Cooperative Extension

A common fungal leaf disease of oak in Arkansas is Oak Leaf Blister, caused by Taphrina caerulescens. All oak species are vulnerable with red oaks being particularly susceptible.

What causes oak leaf blister?

Prolonged periods of cool, wet weather in the spring are conducive for disease development.

What are the symptoms of oak leaf blister?

Symptoms become apparent in early summer as yellow, blisterlike, circular, raised areas, 1/16 to 1/2 inch in diameter. The blisters are scattered over the upper leaf surface with corresponding gray depressions on the lower surface. As the spots age, they turn from yellow to brown with pale yellow margins, becoming dull brown in color. Several blisters may coalesce and cause the leaves to curl. Although unsightly, the disease usually does not greatly impact tree health.

How do I control oak leaf blister?

Control consists of raking up all fallen leaves and twigs, and the application of preventative fungicides where practical. Practicality usually depends on tree size as most homeowners are unable to reach the canopy of large oaks. One application of Chlorothalonil, copper, or mancozeb during dormancy is effective. Fungicides do not have any effect after bud swell in the spring.

Oak Leaf Blister - Taphrina caerulescens. Photo by Sherrie Smith, University of Arkansas System Division of Agriculture Cooperative Extension

Take Aways:

• Rake up all fallen leaves.
• Apply a fungicide during dormancy if the tree is small enough to make spraying practical.

This work is supported by the Crop Protection and Pest Management Program [grant no. 2017-70006 27279/project accession no. 1013890] from the USDA National Institute of Food and Agriculture.

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