Raspberry leaf spot

Raspberry leaf spot, caused by the fungus Cylindrosporium rubi, is a common foliage disease that significantly affects the health of raspberry plants. The pathogen primarily attacks leaves, causing premature defoliation which weakens the plant throughout the growing season.

This fungus is known to infect various species within the Rubus genus, particularly the common raspberry. The disease is widespread in regions with moderate to high rainfall, where the moist environment allows the fungus to thrive and release its spores effectively.

The primary symptom is the appearance of small, circular spots on the leaves. Initially, these spots are brownish with a dark border, but as the infection progresses, the centers turn lighter or white. Dense colonies of fungal spores may develop on the undersides of the leaves, visible during humid conditions.

Disease development is heavily influenced by climatic factors, such as prolonged periods of rain and high humidity. Inadequate air circulation within dense plantings prevents the foliage from drying quickly, creating an ideal microclimate for the fungus to multiply and spread to healthy tissue.

Management and prevention involve a combination of cultural and chemical practices. Crucially, growers must collect and destroy all fallen, infected leaves after harvest to remove the primary source of overwintering inoculum. Additionally, pruning to improve airflow and applying preventive fungicides can keep the infection levels under control.

• Sanitize the planting area by removing debris.
• Ensure adequate spacing between raspberry canes.
• Promote good ventilation within the rows.
• Use copper-based fungicides when necessary.