Raspberry root rot

The causal agent of this disease is the oomycete Phytophthora rubi. It is a severe soil-borne pathogen that targets the root system and the crown of the plant. This disease causes significant disruption in water and nutrient uptake, leading to the rapid decline of infected raspberry bushes.

This pathogen specifically affects plants in the Rubus genus, primarily raspberries and blackberries. It poses a major threat to commercial fruit production, especially in regions with high rainfall or in fields where soil management practices are suboptimal for water drainage.

Symptoms include stunted growth, wilting, and yellowing of the leaves in the spring or late summer. As the disease progresses, the leaves may turn reddish-brown and wither. A definitive diagnostic feature is the necrosis of the roots, which show a dark, reddish-brown discolouration when cut, clearly distinguishing them from healthy white roots.

The development of Phytophthora rubi is highly dependent on environmental moisture. Saturated soil conditions and temperatures between 15°C and 20°C create the ideal environment for zoospore production and dispersal. The pathogen can survive for long periods in the soil through resilient oospores, making it difficult to eradicate once established.

The economic impact of this disease is substantial, as it can cause complete crop failure if left unchecked. Preventive strategies are essential: ensure excellent soil drainage by using raised beds, source certified disease-free plants, and rotate crops. Fungicide applications, specifically those containing phosphonates, are recommended as a preventative measure to help protect the root system.

• Install proper drainage systems in fields.
• Use raised beds to prevent waterlogging.
• Only plant certified nursery stock.
• Apply fungicides as a preventive measure.
• Practice crop rotation and avoid planting on previously infected soil.