Mildew is one of the most important diseases in fruit-growing, mainly occurring in dry, warm regions. In case of a severe infection, yield losses of 40% and above must be anticipated.
Powdery mildew (Apple) [Podosphaera leucotricha]
Leaves and growing tips covered with a mealy-white, later with a gray-green mycelium layer (Pictures 1 & 2). Infected leaves point straight upwards and are rolled up (Pictures 3 & 4). Early shedding of leaves results in a balding of the shoots.
The fungus overwinters in the growing tips and infects the newly formed leaves and inflorescences from there. The visible mycelium layer is the secondary infection during summer. Rains inhibits the fungi development.