Podosphaera leucotricha (Ellis et Everhart) Salmon: Powdery mildew of apple

Apple powdery mildew, caused by Podosphaera leucotricha, is one of the economically most important apple diseases. It is present in all regions where the apple is grown, and it can cause production loss of up to 50%. The appearance of white mycelium on leaves, flowers and shoots is the typical symptom of this disease. If the disease is not managed properly, fruits are not formed, causing direct yield loss. Furthermore, fruit russet appears on the infected fruit, resulting in decreased market value. Disease intensity mostly depends on ecological factors and the susceptibility of the apple variety. Nowadays, significant efforts are being made in order to develop resistant apple varieties, but this goal is yet to be achieved. Management of apple powdery mildew in commercial production is based on chemical control measures, but due to health and environmental concerns, as well as the development of fungicide-resistant populations of the pathogen, it is necessary to find effective biological control methods as an alternative to chemicals.