Peach scab

Venturia carpophila is a filamentous fungus belonging to the family Venturiaceae. It acts as a phytopathogen that primarily targets stone fruit crops within the Prunus genus. Peach, nectarine, and apricot are the most economically affected species, where the fungus causes the characteristic disease known as peach scab.

The fungus manifests through dark, circular lesions on fruits, which often darken and become velvety as conidial production progresses. As the lesions coalesce, the fruit epidermis can crack, leading to severe deformity and stunting. Infections on twigs occur as small, oval-shaped lesions that can persist for several years, acting as critical reservoirs for the pathogen.

The biological cycle involves the fungus overwintering as mycelium in the bark of infected twigs or in mummified fruits left on the tree or the ground. During early spring, the fungus produces conidia, which are disseminated by wind-blown rain to new foliage, blossoms, and developing young fruits. The infection process is highly dependent on humidity and moisture.

Development and spread are favored by frequent rainfall and warm temperatures, typically ranging from 20°C to 25°C. High-density orchards with poor air circulation create the perfect microclimate for the disease to flourish. Without adequate management, the pathogen can quickly colonize the entire canopy, leading to significant yield losses and reduction in fruit marketability.

Control strategies should focus on a multifaceted approach:

• Sanitation: removing all infected twigs and fallen fruit to reduce primary inoculum.
• Pruning: maintaining open canopies to ensure adequate sunlight and air movement, which reduces leaf wetness duration.
• Chemical control: applying fungicides during the bloom and petal fall stages, following a rigorous spray program in regions with high spring rainfall.
• Cultivar selection: choosing resistant or less susceptible varieties where possible.