I hav a tall oak tree next to my driveway. For 2 mornings in a row I have found piles of small branches and attached leaves underneath the tree in the driveway. See attached pix. What is the cause? Squirrels? Also, what are the tiny round nodules on the leaves you can see in one of the pix ?
Oakland County Michigan
Likely squirrels yes, either eating buds or fruit, and/or possibly using the material to build a nest. Could also be twig pruners, the larvae of small beetles that tunnel in twigs and small branches. Female beetles lay their eggs about the time of bud break in the spring. Eggs are laid in small holes which are chewed into the bark. The larvae that hatch from these eggs bore into and tunnel toward the base of twigs. In late summer, they chew concentric circles outward toward the bark then move toward the tip. The twig eventually snaps and falls to the ground. The larva pupates in the fallen twig and emerges as an adult in the spring. Collecting and destroying fallen twigs can help to reduce infestations.eaves look healthy. In either case it should not be a concern for an otherwise healthy tree.
Cannot see the nodules on the leaves through the sunlight but galls, of which there are many, would be the most common. Many are found on oaks and are normally harmless to the tree. Read more here: https://www.canr.msu.edu/news/not_all_galls_are_created_equal_in_the_plant_world
Could also be insect eggs. Oaks are hosts plants to more than 500 species of butterflies and moths. Read more here: http://backyardsfornature.org/?p=1