Question of the Week – Number Two: April 30, 2020

Oak leaf blister has really hit the live oak in the foreground, leaving the more distant one alone altogether. Photo posted to my Facebook page last week by Harold B.

“What has hit my live oak tree? It was fine two weeks ago.”

There was a time last week that every third or fourth post on my Facebook page was about oak leaf blister. I’d get one answered and another one would pop up. This is certainly the year for this fungal leaf disease.

Continued Below

Leaves show the blistering effect of the fungus. Photo posted to Facebook by LST.

The things you must know…
It is caused by a fungus, specifically Taphrina caerulescens.
It’s most common in cool, moist springs.
It attacks tender new growth causing puckered foliage that soon turns yellow, later falling.
It causes little long-term harm to the tree.
There is nothing you can do to cure it once you see it.
If you care to spray to prevent it, you must do so as the buds are just starting to open in very early spring.
I, for one, am not going to spray my live oaks each year on the off chance that one year out of 5 or 20 they might develop oak leaf blister. (That’s not a scientific fact. It’s a personal decision.)
Keep fallen leaves picked up with your mower bagger. They serve as sources of reinfection for next year.

Posted by Neil Sperry
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