Oak Tree

[tboyle]

I have two beautiful oaks in my back yard in Pasadena, Calif. I'm guessing they are 100 years old. Some of the leaves on one of the trees have turned white like some sort of fungus. What should I do?

 

[Darin]

Is this what your problem looks like on this post? http://camfer.cnr.berkeley.edu/oaks/symptoms/dead-leaves.htm

 

[Ray Morneau]

Hello, tboyle --

Your centenarian oaks are likely great assets to you, your property, and your neighborhood/community. I'm glad to see you making such an astute observation and asking such a good question.

Are they deciduous (likely California white oak, valley oak)? or evergreen (likely coast live oak)? Any recent changes (sidewalk, patio, turf, construction, pruning, driveway, breakage, sprinklers, ...)? (Read "recent" for 100-yr old tree is anything in the last 10 to 15 years!) Are both trees affected?

My guess at most likely causal agent is powdery mildew. Can be a drain on the trees' viability/resources. Could spread. UC recommends "Avoid cultural practices which stimulate excess growth, such as [frequent] summer irrigation and heavy pruning. Prune out infected growth in winter. Rake and dispose of infected leaves." (Publ. 3359 Pests of Landscape Trees & Shrubs - An Integrated Pest Management Guide )

Hope this helps. If further questions, ask!