Answer: Oak trees tend to lose inner branches (less than one inch in diameter) as a natural process of thinning. Usually they drop during the winter, not the summer. Root stress can cause early thinning, as can a disease called Diplodia canker. This is a fungal disease and affects both twigs and branches. It often affects shaded or weak branches that are ?next year?s deadwood?. Another common problem is twig dieback. It, too, is caused by fungus. I'd carefully inspect the fallen stems for evidence of black spores or other fruiting bodies, galls, callouses, etc. If you find none, it's just a natural thinning. If you do find spores or other evidence of fungal disease you can spray your tree with a copper based fungicide or with a lime/sulfur (called Bordeaux) in the late winter or early spring. Good luck with your tree.
Q&A Library Searching Tips