Major economically important tree fruit, such as apple (Malus × domestica), pear (Pyrus spp.), and stone fruit (cherry, apricot, peach: Prunus spp.), are amongst the most susceptible crops to powdery mildews. The fungus mostly affects vegetative tissues but can also infect the reproductive organs (flowers and fruits) of the tree. In the absence of appropriate management, severe polycyclic infections may significantly reduce fruit set and yield. This chapter summarizes current knowledge on the biology, epidemiology, host resistance and control of powdery mildew species of apple (Podosphaera leucotricha) and cherry (Podosphaera clandestina). The chapter looks ahead to future research trends in this area and provides detailed guidance for further reading on the subject.