Phoma leaf spot of aubrietia

Phomatodes aubrietiae (formerly classified as Phoma aubrietiae) is a fungal pathogen responsible for causing leaf spot disease, primarily affecting Aubrieta species. This fungus is a specialized parasite that attacks plants within the Brassicaceae family, often compromising their health and aesthetic value in rock gardens.

The disease targets leaves and stems, leading to necrosis of the tissues. As a result, the plant loses its vitality and becomes susceptible to further environmental stress. In severe cases, the entire plant may collapse if the fungal infection reaches the crown or root collar zone.

Symptoms typically manifest as small, circular or irregular spots on the foliage, which are brown or grayish in color. Within these lesions, the fungus produces pycnidia — small black fruiting bodies that are easily visible with the naked eye. These structures are the primary source of secondary infection spreading through the plant.

The spread of this pathogen is highly dependent on environmental conditions, particularly high humidity, frequent rainfall, and stagnant air around dense foliage. The spores are dispersed by splashing water during rain or irrigation. The fungus can survive the winter months in debris and soil, making it a recurring problem if not managed properly.

Management and prevention focus on creating unfavorable conditions for the fungus. This includes improving soil drainage, practicing proper irrigation techniques by avoiding overhead watering, and ensuring adequate spacing between plants to allow airflow. Chemical control using suitable fungicides is recommended when cultural practices alone are insufficient to manage the outbreak.

• Improve air circulation through proper pruning.
• Avoid overhead irrigation to keep foliage dry.
• Remove and destroy all infected plant debris promptly.
• Apply preventative copper-based or systemic fungicides.