I re-plant volunteer oak seedlings which pop up in my back field (Squirrels...
I re-plant volunteer oak seedlings which pop up in my back field (Squirrels do the original plantings.). The photo attached shows "fuzzybuggers" on the upper sides of the leaves. Are these woolly orbs any kind of disease vector indicating the health of the seedling. Alas, I can't identify which species of oak these various seedlings are (The squirrels don't say much.) A complicating factor may be that not all of my volunteer oak seedlings exhibit these growths on the leaves. All seedlings seem to be in otherwise robust health. Thanks, again, for any insight you can provide.
These are 'hedgehog' galls and are 'egg cases' of Cynapid wasps. They are harmless to the tree. You may wish to do some additional research on these wasps and their life cycle. The following publication is quite informative.