Strawberry leaf spot

Strawberry leaf spot is a common fungal disease caused by the pathogen Marssonina potentillae (syn. Diplocarpon earlianum). It primarily affects the foliage, petioles, and calyxes of strawberry plants, leading to a significant reduction in plant vitality and overall yields if not managed properly.

The disease typically affects cultivated strawberries. It is prevalent in many regions where humidity levels remain high, as the pathogen thrives in environments that allow for the germination and spread of its conidia (spores) across the surface of the strawberry leaves.

Symptoms initially appear as small, dark purple or reddish-brown spots on the upper surface of the leaves. As the disease progresses, the centers of these spots often turn light grey or white, while the edges remain dark. In severe cases, these lesions coalesce, causing the leaf tissue to wither and die prematurely.

The development of the fungus is accelerated by prolonged periods of wet, rainy weather and moderate temperatures. It overwinters on infected plant debris left on the field, which serves as the primary source of inoculum for the next growing season, especially in fields with poor drainage or air circulation.

The economic impact is significant due to the loss of photosynthetic leaf area, which directly impairs the plant's ability to store carbohydrates for winter dormancy and spring growth. Growers may see a marked decline in berry size and quality, as well as an increased vulnerability to winter kill or secondary pathogens.

• Practice crop rotation to prevent the accumulation of pathogens in the soil.
• Remove and destroy infected plant foliage after the harvest is complete.
• Use drip irrigation instead of overhead sprinklers to keep foliage dry.
• Apply certified disease-resistant strawberry cultivars in high-risk areas.
• Implement a scheduled fungicide spray program during the pre-flowering and post-harvest stages.