Oak Leaf Blister
Gary W. Moorman, Professor of Plant Pathology
Oak leaf blister, caused by the fungus Taphrina caerulescens, occurs on most species of oaks.
- Spots on the leaves 1/4" - 1/2" in diameter turn light green as young leaves expand.
- Cells in the spots multiply more than surrounding cells and result in a raised blister-like buckling of the leaf.
- As the spots age their upper surfaces become covered with a buff-white coating of fungal growth that later turns brown.
- The leaves remain on the tree and do not fall prematurely.
Cool, moist conditions are required for this disease to occur. The fungus only infects young emerging leaf tissue in the spring, entering the stomates and growing between the leaf cells. The new spores of the fungus formed on the surface of the spots are blown to new buds and remain dormant there until the next spring. Thus, the fungus has only one infection period in the spring and does not continue to cause new spots to form later during the growing season.
Management In The Landscape
Fungicide application is not necessary because the leaves are seldom severely spotted and do not fall prematurely. Although infections may be extensive some years, little damage actually results.
Management In The Nursery
To prevent spotting, fungicide must be applied prior to bud break, late in dormancy. Once bud break has occurred and symptoms are visible, it is too late to spray.
Notice: The user of this information assumes all risks for personal injury or property damage.
Warning! Pesticides are poisonous. Read and follow all directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams or ponds.
Issued in furtherance of Cooperative Extension work, Acts of Congress, May 8 and June 30, 1914, in cooperation with the U. S. Department of Penn State College of Agricultural Sciences research and extension programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.
Visit Penn State Extension on the web at extension.psu.edu.
Where trade names appear, no discrimination is intended, and no endorsement by Penn State Cooperative Extension is implied.
This publication is available in alternative media on request.
The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities. It is the policy of the University to maintain an academic and work environment free of discrimination, including harassment. The Pennsylvania State University prohibits discrimination and harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, gender identity, or veteran status. Discrimination or harassment against faculty, staff, or students will not be tolerated at The Pennsylvania State University. Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA 16802-5901; Tel 814-865-4700/V, 814-863-1150/TTY.