Diseases

Apple Powdery Mildew

Malus domestica (Suckow) Borkh.

A fungal disease of apple trees caused by the obligate parasite Podosphaera leucotricha. It is characterized by the appearance of a grey-white coating on young shoots, leaves, and inflorescences, causing them to deform and wither.

In the reference 1 127 varieties crop Apple, where this is mentioned in the description.

The pathogen is the fungus Podosphaera leucotricha (anamorph Oidium farinosum), which primarily infects non-lignified plant parts via haustoria. The pathogen overwinters as mycelium inside fruit and vegetative buds, from which infected shoots develop in the spring.

The disease manifests as a powdery coating, which eventually acquires a reddish hue. Affected leaves curl and lose turgidity, inflorescences become deformed and drop, and a characteristic 'russet netting' may form on the fruit.

In apple breeding for resistance to the pathogen, the introgression of specific genes, such as Pl-1, Pl-2, Pl-w, and Pl-d, plays a key role. Molecular marker methods are used to identify resistant genotypes, often in combination with scab immunity assessment.

General information about the subject — on the page Powdery mildew.

Sources8

Varieties of Apple mentioned in the description

Selection based on the description text, not on official evaluation: these data are absent from registers. For specific variety details, please refer to its profile.