If you have noticed your oak leaves with odd bumps or coloring, or the oak tree losing leaves out of season, you oak tree may have a leaf spot disease. Wet springs can lead to fungal infections later in the year. These fungal disease can cause your oak trees to lose leaves out of season. Usually the leaf spot diseases are not terrible. While it is distressing noticing your tree losing lots of leaves out of season, it normally will not affect the overall health of the tree. If the tree is already stressed however, it could be detrimental.
Pesticide use is not recommended, but if used it will need to be applied at tree bud break or when the tree is putting on a flush of new growth. By the time the tree leaves show symptoms it is too late to apply pesticides.