How to recognize and combat black spot (Phyllosticta) on fruit

Phyllosticta sp. is a genus of ascomycete fungi that includes numerous species associated with different crops and plants, some of which can significantly affect fruit. Species in this genus can behave as pathogens of living plant tissues and also develop on weakened or dead tissues, depending on the species and the crop affected. The fungus develops a mycelium composed of hyphae that colonize infected tissues and can form reproductive structures called pycnidia, within which numerous conidia are produced. These pycnidia usually develop within lesions and constitute an important source of inoculum. In some species, sexual structures such as pseudothecia can also be produced, which generate ascospores and can contribute to the dispersal and emergence of new infections. The pathogen can survive between favorable periods in affected fruits, plant debris, branches, leaves, and other infected tissues that remain in the crop or in the soil. When environmental conditions are favorable, the reproductive structures release conidia, especially in the presence of free water or high humidity. Conidia can be transported by raindrops, water splashes, and other short-distance dispersal mechanisms, reaching the surface of healthy fruit. Once deposited on susceptible tissue, conidia can germinate and form germ tubes that penetrate the tissues, especially where wounds, micro-fissures, or weakened areas are present. Prolonged moisture on the fruit surface favors germination and the establishment of the infection. After penetration, the fungus develops mycelium within the tissues and causes localized cell death, resulting in characteristic lesions. As the infection progresses, new pycnidia can form in the affected areas, where new conidia are produced that can cause secondary infections. In certain species, infections can remain latent for a period and become visible later, especially when the fruit ripens or is subjected to stress, mechanical damage, or favorable environmental conditions. The disease can become particularly important during storage and preservation, as some fruits may exhibit infections that are barely visible at harvest but progress subsequently. The amount of inoculum present, the susceptibility of the fruit, the presence of wounds, and the duration of periods of humidity are determining factors for the appearance and spread of the disease.