pest in my oak tree
Left photo - This looks like a type of foliar disease called anthracnose on the oak foliage. We have had many questions regarding this. Anthracnose can be prevalent during cool wet springs followed by warm weather. You may notice browning along the leaf veins, etc. Anthracnose can affect oak, sycamore, ash, maples, etc. No control is necessary.
Rake all fallen leaves to prevent overwintering spores. See our website for photos and more information http://extension.umd.edu/hgic/shade-tree-anthracnose-trees
Right photo - looks like old chewing damage from a caterpillar. This was most likely done when the leaves were new and tender. The caterpillar or critter is gone.
The oak should recover and no treatments are necessary.
In general, we do not recommend Sevin. This is a broad spectrum insecticide that kills all insects including beneficials that help control pests naturally.
Thank you very much. Your answers have been extremely helpful.
You are welcome.