This may be Kinsey's Neuroterus dubius.
Small fuzzy galls on the male flowers of Quercus macrocarpa in spring. Two galls matching this description have been observed. In one case the hairs were sparse enough to reveal a dark gall in a rounded-conical shape. In the other their shape was concealed in a thick layer of long white hairs.
Observed in Manitoba in May and June.
”- Gallformers Contributors: (2024) Gallformers ID Notes©