Pear scab

Pear scab is a widespread and destructive fungal disease caused by the ascomycete Venturia pyrina. This pathogen is host-specific to pear trees and is responsible for significant reductions in fruit quality and yield, often causing severe cosmetic damage that renders fruit unmarketable.

The fungus attacks all green parts of the tree, including leaves, flowers, twigs, and developing fruit. High humidity, frequent rainfall, and mild temperatures during the early growing season create the ideal environment for the rapid germination and spread of fungal spores across the orchard.

Initial signs of the infection include the appearance of olive-brown spots with a velvety texture on the undersides of leaves. As the disease progresses, these spots darken and coalesce. On fruit, scab manifests as dark, corky lesions that often crack, leading to significant fruit malformation and stunted growth.

The pathogen overwinters primarily in infected fallen leaves on the orchard floor. When spring rains occur, sexual spores (ascospores) are released into the air and carried by wind and water to young, susceptible host tissues, initiating the primary infection cycle for the new growing season.

Successful management of pear scab requires an integrated pest management (IPM) strategy that combines several approaches:

• Rigorous orchard sanitation, including the removal and destruction of fallen leaves.
• Pruning techniques designed to promote air circulation and reduce canopy moisture.
• Well-timed fungicide spray programs, focusing on critical infection windows in spring.
• Monitoring weather patterns to apply preventative treatments before infection events.
• Selecting and planting pear varieties that show natural resistance to the pathogen.