Chestnut cytospora canker

Chestnut cytospora canker is a destructive fungal disease caused by the pathogen Cytospora parasitica. This fungus primarily targets the bark and cambial tissues of chestnut trees, leading to the formation of cankers and subsequent dieback of branches or the main trunk.

The disease affects various chestnut species, particularly the sweet chestnut. Pathogens typically invade through vulnerable entry points such as frost cracks, sunscald injuries, pruning wounds, or mechanical damage caused by agricultural machinery or wildlife.

Visible symptoms include localized bark discoloration, turning from healthy brown to reddish or dark sunken areas. As the disease progresses, the fungus produces small, pimple-like fruiting bodies known as pycnidia on the bark surface. During humid weather, these structures release spores that spread the infection to neighboring trees.

The development and spread of Cytospora parasitica are favored by stressful environmental conditions, including prolonged drought or rapid temperature fluctuations that weaken the tree's physiological state. Once established, the fungus colonizes the inner bark, effectively girdling stems and disrupting the tree's vascular system.

Management of cytospora canker relies heavily on sanitation and cultural practices. It is essential to prune out infected branches well below the point of obvious damage and dispose of the debris properly. Applying protective fungicides to pruning wounds and maintaining tree vigor through adequate irrigation and nutrition are vital to preventing further disease progression.

• Prune and destroy infected branches immediately.
• Disinfect all pruning tools between cuts.
• Apply wound paint or copper-based fungicides to large cuts.
• Avoid mechanical stress to the bark of the trees.