Sphaerotheca lanestris
Hosts: Quercus agrifolia, wislizeni, chrysolepis, lobata; Notholithocarpus densiflorus
A powdery mildew that initiates white witches' brooms on new shoots, which are commonly produced only in spring and early summer.
”- Russo, Ronald A. : (2021) Plant Galls of the Western United States©