Spur blight

The fungus Xenodidymella applanata is the causal agent of spur blight, a widespread disease affecting raspberry canes. It belongs to the group of ascomycetes and thrives in temperate climates, causing significant damage to commercial berry plantations and home gardens alike.

The primary host for this fungus is the raspberry plant. However, it can occasionally infect blackberries. The pathogen spreads through ascospores and conidia, which are easily dispersed by wind, rain splashes, and insects, landing on the succulent tissues of young shoots.

Disease symptoms typically appear in the summer. They manifest as purple or brown spots on the canes, usually centered around the leaf nodes. As the infection progresses, the spots expand and turn grey or black, causing the bark to crack and the buds to die off, which prevents the development of fruit-bearing lateral branches.

Development and spread of Xenodidymella applanata are highly dependent on environmental factors. High humidity, heavy rainfall, and temperatures ranging from 18°C to 25°C favor spore germination. Poor air circulation caused by overcrowding or excessive weed growth significantly increases the severity of the outbreak.

• Prune and destroy infected canes immediately after harvest.
• Space plants properly to ensure adequate airflow and light penetration.
• Apply fungicide sprays during the spring growth phase.
• Remove weeds that contribute to excessive moisture around the base of the plant.
• Choose resistant cultivars to minimize the risk of infection.

The economic impact of spur blight is considerable, as it leads to reduced yields and weakened cane structure. Infected canes are more prone to winter injury and desiccation. If not managed properly, the disease can reduce the lifespan of the raspberry plantation and compromise fruit quality significantly.