Stagonospora leaf spot of strawberry

The fungus Stagonospora fragariae is the causative agent of the strawberry leaf spot disease known as stagonospora. This pathogen survives the winter in infected leaf tissues and crop debris, releasing spores that initiate primary infections when favorable environmental conditions arrive during the spring months.

This disease primarily targets garden strawberry (Fragaria × ananassa) plants. While it is highly host-specific, it can cause significant stress to strawberry plantations, particularly in regions where the crop is cultivated repeatedly on the same plot without proper rotation or site sanitation practices.

Symptoms of the infection typically appear on the leaves. Initially, small, reddish-purple to brown spots form on the leaf surface. As the infection progresses, the centers of these spots turn grayish or necrotic, often surrounded by a darker border. Under high humidity, small black fruiting bodies called pycnidia develop within the spots, releasing spores to spread the disease.

Fungal development is highly dependent on environmental conditions, particularly temperature and moisture. The disease thrives in moderate temperatures and during periods of frequent rainfall or high humidity. Wind, splashing water, and movement of infected garden tools are the main vectors that disseminate the pathogen throughout the field.

The impact of stagonospora on yield can be significant, as heavy infection leads to reduced photosynthetic capacity, premature senescence, and overall plant decline. Effective management strategies include:

• Removal and destruction of infected plant debris after harvest.
• Ensuring proper spacing to improve air circulation within the canopy.
• Application of preventative fungicides during periods of high disease pressure.
• Use of disease-free planting stock for new beds.