Leucostoma canker

Leucostoma canker, caused by the fungal pathogen Leucostoma cincta, is a devastating disease affecting stone fruit trees. This fungal infection primarily targets the bark and cambium, leading to necrotic lesions that interfere with nutrient transport, often resulting in limb dieback or the eventual death of the tree.

The pathogen hosts a wide variety of stone fruit species, including peaches, apricots, plums, cherries, and almond trees. Infection typically occurs through wounds in the bark, which can be caused by pruning cuts, winter frost cracks, sunburn, or mechanical damage from orchard equipment.

Common symptoms include sunken, dark-colored lesions on the bark, which often exhibit significant gumming (gummosis) as the tree attempts to wall off the infection. As the disease progresses, the epidermis of the infected area develops tiny, pimple-like structures known as pycnidia, which release spores during wet weather to infect adjacent parts of the tree.

The development and spread of Leucostoma cincta are heavily influenced by environmental conditions, particularly high humidity and fluctuations in temperature during the dormant season. The fungus is persistent, overwintering in infected branches and twigs, and can remain active as long as the host tissue remains moisture-retaining and vulnerable.

Effective management and prevention of the disease require a multi-faceted approach to reduce the pathogen's pressure in the orchard:

• Strict sanitation, including the pruning and removal of all diseased wood.
• Disinfecting pruning tools to prevent the cross-contamination of healthy trees.
• Proper site selection and tree care to minimize winter and sun-related injuries.
• Application of protective copper-based fungicides during the dormant season.
• Maintaining tree vigor through balanced fertilization and appropriate irrigation to improve natural defense.