Leaves turning yellow and brown with red spots on them.

[FromCali]

Leaves of the oak tree are turning yellow and brown. There are Red Tip Photinia under the oak tree and their leaves are turning yellow with red spots on them. Do you know what is going on?

 

[Tetters]

Why Are My Oak Tree Leaves Turning Brown? | Davey Blog | Davey Tree

Is my oak tree dying? Is this oak wilt? The key to diagnosing your browning oak tree is looking past the color and checking for other signs and symptoms.

blog.davey.com

Hi, I was pretty sure your red tip photinia had a fungal infection, which is best controlled by clearing all fallen leaves and keeping everything extra clean, including using a new mulch around the tree to cover any spores that are left behind, but I was quite unsure about the California oak. I have found a link that I thought was interesting, and am hoping it will help you to sort the problem out.

 

[cpp gardener]

So Oak Wilt is out, it only occurs East of the Mississippi.
What’s your watering program?
What’s your fertilizing program?
How much of the tree is affected?
On the Photinia, it is a bacterial leaf spot and can be treated with a copper spray between now and April.

 

[Tetters]

Glad you came to the rescue @cpp gardener as the OP was getting no replies

 

[FromCali]

So Oak Wilt is out, it only occurs East of the Mississippi.
What’s your watering program?
What’s your fertilizing program?
How much of the tree is affected?
On the Photinia, it is a bacterial leaf spot and can be treated with a copper spray between now and April.

The entire oak tree is like that.
We only water and that might be enough, and don't have any fertilizing program.

 

[FromCali]

So there is no connection between Oak tree and Photinia? I am asking because Photinia under Oak tree seems affected, but Photinia which are note under Oak tree seems better.

 

[cpp gardener]

It's due to the shade of the oak tree. The Photinia grows more vigorously in the sun and can ward off the bacteria. The air is also drier out in the sun which reduces the favorable environment for the bacteria.
The extra rain you got last winter may also have affected both the oak and the Photinia. Different bacteria but better environment for infection. All that extra humidity makes it that much better for bacterial infections. If there's less rain this winter there should be less damage next year.