White oak with brown leaves
I have noticed that there are clusters of brown leaves on oak trees around my home and in the general vicinity of my acreage. The brown clusters are distributed amid the green leaves. I have lived in this area for over 40 years and have never seen this. I noticed clusters of brown leaves on oak trees last winter and wondered why they had not fallen. I dont know that clusters I am seeing now are the same ones. I live south of Philomath, Oregon in the Willamette Valley where aerial spraying occurs but it seems that if spraying were the cause the leaves would have dropped off in the winter. I checked on white oak diseases and saw a picture of an oak that resembled what I am seeing in my area. The picture that matched was showing the effects of drought. Drought is not the case where I am living.
Benton County Oregon trees and shrubs
What you're seeing is usually described as 'flagging' where individual leaves or bunches of leaves turn brown. It's hard to know what exactly is going on with the oaks in your area without actually observing the flagging areas up close. Insect feeding or breeding, plant diseases or even squirrel feeding & nesting activities can result in flagging symptoms.
If there are any affected branches that are low enough to reach, feel free to collect a sample. You can bring it in to the OSU Extension Benton County office and the Master Gardeners should be able to determine what is causing the problem.
Here is their contact information: http://extension.oregonstate.edu/benton/
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