Black rot of apple

Black rot is caused by the fungus Physalospora malorum (anamorph Sphaeropsis malorum), a serious disease that affects the bark, wood, and fruit of apple trees. It is a widespread pathogen that significantly impacts yield quality and tree longevity in apple-growing regions.

The fungus has a broad host range within the Rosaceae family, primarily infecting apple and pear trees. It can manifest at any growth stage, but is most frequently observed on mature trees suffering from environmental stress or poor orchard management.

Symptoms appear as reddish-brown spots on the bark that expand into necrotic, blackened, and cracked lesions. Infected fruit develop firm, brown to black circular lesions, eventually becoming mummified and covered in small, black, pin-like fungal fruiting bodies known as pycnidia.

Disease development is highly dependent on humidity and temperature. Spores are disseminated primarily by splashing rain and wind, entering the tree through wounds created by pruning, hail, frost cracks, or sunscald. The fungus persists in dead bark or infected mummified fruit left on the tree or the ground.

Control measures emphasize integrated pest management. Key strategies include pruning and disposing of infected branches, ensuring proper tree sanitation, avoiding unnecessary wounding, and applying protective copper-based fungicides during the growing season to prevent initial infection and spore spread.