Pear bark necrosis

Pear bark necrosis is a serious fungal condition primarily caused by pathogens such as Cytospora leucostoma. It attacks the bark and cambium layers of the tree, effectively disrupting the vascular system and potentially leading to branch dieback or total tree mortality if left unchecked.

While the pear tree is the primary host, this disease is opportunistic and often targets weakened trees. Factors that compromise tree integrity, such as frost cracks, sunscald, improper pruning wounds, or heavy infestations of wood-boring insects, provide the ideal entry points for fungal spores to colonize the bark tissue.

The diagnostic signs include discolored, sunken, or cracked bark patches on the trunks and major limbs. As the disease progresses, these lesions often produce tiny, pimple-like fruiting bodies (pycnidia) of the fungus. If the infection circles the branch or trunk, the parts of the tree above the lesion will inevitably wither and die.

Fungal development is favored by cool, wet weather and stagnant air circulation within the canopy. The spores are easily dispersed by rain splash, wind, or contaminated pruning tools. Orchards with poor hygiene and high density are particularly susceptible to rapid outbreaks during damp spring months.

• Prune out and destroy infected branches at least 15 cm below the visible lesion.
• Disinfect all pruning tools between cuts with a 70% alcohol solution or bleach.
• Paint trunks with white latex paint to prevent sunscald.
• Apply copper-based fungicides during dormancy to reduce inoculum.
• Maintain tree vigor through balanced fertilization and adequate irrigation.

Long-term control relies on creating an environment where the tree is not under stress. Regular monitoring for early symptoms and immediate surgical removal of infected bark tissues are the most effective strategies to prevent the disease from spreading throughout the entire orchard.