White or gray powdery growth on leaves, shoots or fruit can indicate powdery mildew.
Common fruit hosts
UC IPM identifies apples, nectarines, peaches, cherries, grapes, plums and several berries among susceptible fruit crops, with susceptibility varying by cultivar.
California climate
Powdery mildews can perform well in Mediterranean climates and do not require free water on plant surfaces to continue growing after infection.