Question
Oak leaf fungus?
Hi
My very large white oak appears to have some leaf blight problem. Attached are a few pictures of the difficulty. Leaves are disfigured w/ splotches. I'm in Maryland near the northern boarder of Washington DC. Thank you for your help.
AnswerThese are leaf spots caused by a fungus called leaf blister. Oak leaf blister is a fungal leaf spot disease caused by the fungus Taphrina deformans. It is a spring disease common on all oak species. Severe leaf blister can result in widespread early defoliation. With well-established trees, early defoliation will not cause tree death, but it will reduce tree vigor and aesthetics.
Early in the spring, small, rough (concave-convex) spots will begin to appear as the leaves expand. Gradually, the spots will become pale green in color and somewhat thickened. Older spots are brown or greenish brown. Leaves with numerous spots will fall prematurely to the ground. If well-established trees defoliate before midsummer, they will sometimes leaf out later in the season. When defoliation occurs in the late summer, leaf loss will have little impact on the tree's health.
Because oak leaf blister does not seriously affect the overall health of the tree, chemical control measures are usually not recommended. Likewise cultural controls are ineffective because of the nature of the fungus and its method of infection and transmission. The following strategies for limited control of oak leaf blister are recommended:
Collect and discard fallen leaves.
On small, newly established or especially valuable specimen oak trees previously damaged by leaf blister, apply a protective fungicide. Apply the fungicide at bud swell.
The following fungicides are labeled for use on oak to control oak leaf blister: Bordeaux mixture, Daconil Ultrex, Daconil Weather Stik 6F, Rose and Shrub Disease Combo, Dithane M-45 80W, Fore 80W. Always follow label recommendations and precautions.
