Oaks loosing limbs
I have 2 oaks that have looked much better in the past. They are both about 25 years young and this year the second one of the two has started to show signs of deterioration. I am trying to find out what the issue is. Photos show complete tree, leaves with disease (?), and other unknowns. Very few leaves show signs of disease. Bark looks good, but I’m not sure what to look for. Obviously, these are young leaves. Please let me know what you think and any treatment. I can send more photos if it helps. They have been beautiful trees in the past and I hope to bring them back to their glory.
Our plant pathologist and our entomologist both looked at your photos. The tree on the left is clearly in decline. It is possible that it has been affected by bacterial leaf scorch in the past. Scorch symptoms typically appear in mid to late summer on lower branches as irregular marginal browning on interior leaves. Take a look at our website for further information on leaf scorch. Unfortunately, there is no cure for it. https://extension.umd.edu/hgic/bacterial-leaf-scorch-trees
It is difficult for us to see in the photo, but it looks like there might be some damage at the base of the trunks. Physical damage to a trunk can lead to branch dieback symptoms as well.
In addition, oaks can decline gradually over time if they are exposed to other stressors (e.g., periods of drought stress). https://extension.umd.edu/hgic/topics/natural-decline
The round structure in your last photo is an oak apple gall. These are growths produced by the tree in response to an insect. They are very common on oaks and are not a cause for concern. https://extension.umd.edu/hgic/topics/shade-tree-galls
We're sorry to see your oaks in decline. Here is a helpful page on how to decide when to remove a tree. https://extension.umd.edu/hgic/topics/how-do-you-decide-when-remove-tree