Peach scab

Taxonomic position and pathogen type. Cladosporium carpophilum (synonym Venturia carpophila) is a significant fungal pathogen belonging to the Kingdom Fungi. It is the primary cause of peach scab, a common and destructive disease affecting stone fruits worldwide, significantly impacting commercial production.

Host crops and symptoms. The pathogen primarily attacks peaches, nectarines, apricots, and almonds. Symptoms manifest as small, circular, dark green to olive-colored spots on the surface of fruit, leaves, and twigs. As the disease progresses, these spots darken and coalesce, frequently leading to the cracking of the fruit skin, which compromises fruit quality and market value.

Biology and life cycle. The fungus overwinters primarily as mycelium in the lesions of twigs from the previous season. In the spring, when temperatures rise and humidity increases, the fungus produces conidia, which are disseminated to young fruit and leaves by wind and splashing rain. The disease can persist throughout the growing season if environmental conditions remain favorable for spore production.

Developmental conditions and impact. The pathogen thrives in warm, humid climates, with frequent rainfall being the most critical factor for spore dispersal and infection. Dense canopy foliage that prevents rapid drying after rain also creates an ideal microclimate for the disease to flourish. Economic losses arise from the fruit becoming disfigured and unmarketable, as well as reduced tree vigor due to twig infections.

Protection and control measures. Successful management relies on an integrated approach:

• Regular pruning to remove infected twigs, which are the primary sources of overwintering inoculum.
• Timely application of protective fungicides during bloom and early fruit development stages.
• Proper orchard sanitation, including the removal and destruction of fallen infected fruit and leaves.
• Ensuring good orchard ventilation through canopy management to reduce prolonged wetness periods.