Phoma dieback of roses

Causative agent and type of disease
The causative agent of Phoma dieback of roses is the fungus Calophoma rosae (formerly Phoma rosae), which belongs to the Coelomycetes class. This fungal pathogen primarily affects the stems of rose bushes, typically entering through wounds caused by pruning, environmental stress, or frost damage.

Affected plants
The disease mainly affects the genus Rosa. It is commonly found in a wide variety of rose types, including hybrid teas, climbers, and landscape roses. Nurseries and dense plantings are particularly susceptible, as the environmental conditions there often favor the rapid spread and establishment of the fungal spores.

Symptoms and signs of infection
Infection manifests as distinct spots on the stems, which initially appear as small, light-colored or brownish lesions with a darker margin. As the pathogen matures, tiny black fruiting bodies known as pycnidia develop within the central area of the spots. If the infection spreads around the circumference of a stem, the distal part of the branch often wilts and dies back.

Conditions for development and severity
The development of Calophoma rosae is promoted by high humidity, prolonged rainy weather, and mild temperatures. Spores are disseminated by water splash, wind, or contaminated pruning tools. The impact of the disease includes structural damage to the stems, reduced plant vigor, and in severe cases, the complete death of the affected canes.

• Sanitary pruning of all infected stems, ensuring tools are disinfected frequently.
• Burning or proper disposal of diseased plant material to reduce spore load.
• Application of copper-based fungicides or systemic treatments during the dormant season.
• Maintaining proper plant spacing to ensure adequate air circulation and foliage drying.
• Promoting overall plant health through balanced nutrition and proper watering practices.