The yellowing of oak leaves at this time of year is quite normal. When we have a year like this one with very unusual weather conditions, i.e., extreme cold early in the year, periods of extreme drought followed by periods of extreme rainfall, etc., we should not expect our trees to respond as they normally do.
The little fuzzy balls, called oak galls, are a common occurrence caused when the tree reacts to tiny, non-stinging wasps laying their eggs on its leaves, branches, twigs or flowers. These insects inject a hormone into the plant tissue, causing it to grow abnormally and enclose the developing wasp larvae. Galls come in all shapes, sizes, colors and textures. Oak trees, in particular, appear to get many different types of galls.
Like many insects, populations of gall insects will vary from year-to-year. Consequently, in some growing seasons, some species of galls will be more plentiful than in other years. While galls may appear threatening, based upon their appearance, most galls actually pose very little threat to overall tree.
While the information in the link below is not from a research university such as MSU, I think the information is accurate and you may find it interesting re. oak galls.
Acorns belonging to trees in the red oak group take two growing seasons to mature. Spring oak blossoms will not mature to an acorn for 16-17 months. Although these trees require two years to produce an acorn crop, they flower every spring, whether or not they have immature acorns.That means they also have the potential to produce a crop of acorns every year as long as the conditions for fruit-set are favorable. Bumper crops for reds are usually about five years apart. Incidentally oaks generally do not begin producing acorns until they are about 30 years old!
The two main factors that affect acorn production are spring weather and tree stress.The best acorn crops seem to follow warm spring weather. Acorns require dry weather for about a week in mid-May when the tree produces pollen. The weather during that week is critical to acorn production. If it is cool and wet during the time of pollen production or if a frost hits the tree after it has produced pollen, it will result in a poor acorn crop that fall.
Another factor in acorn production is stress on the trees. Insect defoliation, drought, fungus, and other stresses can limit acorn production. In some years of extreme stress, oak trees will even abort the developing acorn crop in order to redirect nutrients to keeping the tree healthy. In years following a stress event, most of the energy is used to rebuild and heal instead of going toward acorn production. This could cause smaller acorn crops for a few years, even when all other conditions seem perfect. Oak galls do not drain enough energy from the trees leaves cause stress to the tree.