Mespilus germanica
Powdery mildew, caused by the obligate biotrophic ascomycete "Podosphaera leucotricha", is one of the major diseases of cultivated apple throughout the world. The primary host is apple, but other fruit like peaches and quince provide a host for "Podosphaera leucotricha." A list of host plants/species affected includes "Cydonia oblonga" (quince), "Malus" (apple), "Prunus persica" (peach), "Prunus domestica" (plum), "Pyrus" (pears), and "Mespilus germanica" (medlar). On apples, the fungus affects twigs, foliage, blossoms, and fruits of current season growth. Infected plants are characterized by reduced photosynthesis and transpiration, resulting suboptimal carbohydrate assimilation and reduced growth.