Coral spot

Coral spot is a common and destructive fungal disease caused by the pathogen Tubercularia nigricans (the asexual stage of Nectria cinnabarina). This fungus typically invades the bark of trees and shrubs, leading to the development of necrotic lesions and the eventual death of affected branches.

The disease affects a wide range of woody hosts, particularly focusing on deciduous trees and shrubs. Common victims include apple, pear, and plum trees, as well as ornamental species such as maples, lindens, lilacs, and horse chestnuts, especially when plants are already stressed or suffering from environmental damage.

The primary diagnostic symptom is the appearance of small, hard, coral-red or pinkish fungal cushions emerging through the bark. As the infection progresses, the underlying wood becomes discolored and brittle, and the bark eventually splits and peels away. In severe cases, the entire branch will wither and die back.

Environmental conditions play a critical role in the spread of coral spot. High humidity and prolonged wet weather facilitate the release and germination of spores. The fungus primarily enters the host through wounds caused by pruning, mechanical damage, frost cracks, or sunburn, making healthy maintenance essential to prevention.

Effective management and control strategies include several key practices:

• Prompt removal and destruction of infected branches, cutting well into healthy wood.
• Application of wound sealants or copper-based fungicides to protect open cuts.
• Preventing unnecessary wounds and keeping plants vigorous through proper nutrition and watering.
• Applying preventative fungicide sprays in early spring if the garden has a history of outbreaks.