Oak Leaf Blister: Taphrina caerulescens Symptoms and Control

Symptoms

• Spots ¼–½" diameter turn light green as young leaves expand.
• Cells in spots multiply more than surrounding cells → raised blister-like buckling.
• As spots age, upper surfaces become covered with buff-white fungal coating turning brown.
• Leaves remain on tree, do not fall prematurely.

Cool, moist conditions required. Fungus only infects young emerging leaf tissue in spring, entering stomates and growing between leaf cells. New spores formed on spot surfaces blow to new buds, remain dormant until next spring. Thus, only one infection period in spring; no new spots later in growing season.

Management in Landscape

Fungicide not necessary—leaves seldom severely spotted, don't fall prematurely. Even extensive infections some years cause little actual damage.

Management in Nursery

To prevent spotting, fungicide must be applied prior to bud break, late in dormancy. Once bud break occurs and symptoms visible, too late to spray.

Prepared by Gary W. Moorman, Professor of Plant Pathology.