Calophoma aquilegiicola leaf spot

Calophoma aquilegiicola leaf spot is a fungal disease caused by the pathogen Calophoma aquilegiicola. This fungus acts as a specialized parasite, primarily targeting various species of the Aquilegia genus, leading to necrotic tissue damage and significant physiological stress in affected plants.

The disease affects a wide range of columbine cultivars grown in domestic gardens and professional nurseries. Plants that are densely planted or situated in shaded areas with poor air circulation are particularly vulnerable to initial infection and rapid disease development.

Typical symptoms involve the formation of distinct, circular or irregular spots on leaves, which eventually turn dark brown or greyish as the tissue dies. Closer examination often reveals minute black fruiting bodies, known as pycnidia, scattered across the necrotic lesions, which release spores that facilitate the spread of the pathogen.

Development and spread of the fungus are favored by cool to moderate temperatures and high humidity levels. Rainfall and irrigation water play a crucial role in splashing spores onto healthy leaves. The pathogen is capable of overwintering on plant debris, serving as a primary source of inoculum for the subsequent growing season.

The impact of this disease includes reduced vigor, premature leaf drop, and in severe cases, the stunting of flower development. Effective management requires a combination of cultural and chemical strategies to protect the health of the plants:

• Thorough cleanup and destruction of fallen leaves and infected plant material in autumn.
• Ensuring adequate spacing between plants to promote rapid drying of foliage.
• Avoidance of overhead irrigation to keep leaf surfaces dry.
• Application of appropriate fungicides to protect susceptible foliage during periods of high humidity.