Strawberry white leaf spot

The fungus Ramularia grevilleana is the causal agent of white leaf spot in strawberry plants. This disease is widely recognized in professional horticulture as a significant fungal infection that can severely impact the productivity and longevity of strawberry fields if left unmanaged.

The pathogen primarily affects the leaves of strawberry plants, although under high disease pressure, it can also manifest on petioles, stolons, and sepals. By compromising the photosynthetic area of the canopy, the fungus significantly weakens the plant, often leading to reduced berry size and poor yield quality.

Clinical symptoms include small, circular spots with reddish-purple margins. As the infection progresses, the center of these spots turns white or greyish-white. A diagnostic feature often observed is the necrosis of the central tissue, which eventually falls out, leaving small, irregular holes commonly described as a shot-hole appearance.

Environmental conditions characterized by high humidity, mild temperatures, and prolonged moisture on foliage are ideal for spore germination and infection. The fungus overwinters primarily in the form of mycelium and sclerotia on infected plant debris, which acts as the primary inoculum source for the following season.

Management and prevention focus on integrated approaches:

• Removal and destruction of infected crop debris post-harvest.
• Ensuring proper plant spacing to improve air circulation within the canopy.
• Selecting resistant cultivars adapted to local climate conditions.
• Applying fungicides during the vegetative stage if threshold levels are exceeded.
• Maintaining proper irrigation practices to minimize leaf wetness duration.