Ascochyta leaf spot of leopard's bane

The disease is caused by the pathogenic fungus Ascochyta doronici, an imperfect fungus that primarily affects foliage. It belongs to the group of fungi known to cause localized tissue necrosis through the production of pycnidia, which release spores during favorable environmental conditions.

The primary host for this pathogen is the ornamental perennial known as leopard's bane (Doronicum). The disease manifests mainly on the leaves, though severe infestations can spread to petioles and stems, leading to significant defoliation and reduction in the plant's aesthetic value and overall vigor.

Symptoms typically present as distinct spots on the leaves. These spots are initially yellowish or light brown, later turning dark brown or necrotic with a defined margin. A key diagnostic feature is the presence of small, dark, pimple-like structures (pycnidia) embedded in the center of the lesions, which release spores under humid conditions.

The development and spread of Ascochyta doronici are heavily dependent on environmental factors, particularly high humidity and moderate temperatures. Prolonged periods of rain or heavy dew create ideal conditions for spore germination and infection. Overwintering occurs primarily in infected plant debris left on the soil surface, providing a source of primary inoculum in the spring.

Management of this disease relies on a combination of cultural practices and chemical control. Key strategies include:

• Prompt removal and destruction of infected foliage and plant debris.
• Ensuring adequate spacing to promote airflow and reduce canopy humidity.
• Avoiding overhead irrigation to keep foliage dry.
• Applying preventive fungicide treatments if environmental conditions favor disease outbreaks.