Phoma leaf spot of ivy

Phoma leaf spot of ivy is a fungal disease caused by the pathogen Boeremia hedericola (syn. Phoma hedericola). This fungus is a member of the class Deuteromycetes and is known for specifically targeting evergreen ornamentals, primarily various cultivars of common ivy (Hedera helix).

The primary host is ivy, which is susceptible whether grown outdoors or in indoor greenhouse conditions. The fungus attacks all aerial parts of the plant, including leaves, petioles, and stems. In high-humidity environments, the infection can rapidly spread, compromising the health and aesthetic value of the entire plant.

Typical symptoms include the appearance of irregular, light-brown to greyish-brown spots on leaves, often surrounded by a dark margin. As the disease progresses, small black fruiting bodies, known as pycnidia, develop within these spots. These structures contain spores that facilitate the spread of the pathogen, often leading to premature leaf drop and shoot dieback.

The development of Boeremia hedericola is favored by high humidity, poor air circulation, and moisture accumulation on leaf surfaces. Optimal temperatures for fungal activity range between +18°C and +25°C. Spores are primarily disseminated through splashing water, such as rain or overhead irrigation, and can also be spread by contaminated gardening tools or handling.

The impact of this disease on horticultural crops is significant, as it leads to rapid decline in ornamental quality and potential plant loss. Effective management strategies include:

• Regular removal and destruction of infected foliage and stems to reduce inoculum levels.
• Improving air circulation and ventilation to keep foliage dry.
• Implementing proper irrigation practices that avoid wetting the leaves.
• Applying preventive or curative fungicidal treatments containing copper or systemic active ingredients where permitted.