Gnarly-looking leaf galls are appearing on pin oaks (Quercus palustris) in southwest Ohio. The unsightly, lumpy leaf growths are produced by a gnat-like gall-midge (Macrodiplosis niveipila, family Cecidomyiidae) and I’ve commonly called the growths Gnarled Oak Leaf Midge Galls. Not very creative, but descriptive.
Read more here.