Bacterial decline of hazelnut

Bacterial decline of hazelnut is a severe disease caused by the bacterium Pseudomonas avellanae. This pathogen poses a significant threat to hazelnut orchards globally, as it affects the vascular system and cortical tissues, leading to necrosis, wilting, and potential death of the trees if the infection is not managed effectively.

The primary host for this pathogen is the hazelnut tree (Corylus avellana). The bacteria enter the plant through natural openings, such as buds and leaf scars, or via wounds inflicted during pruning or caused by mechanical damage. Once inside, the bacteria multiply rapidly within the tissues, disrupting nutrient transport.

Symptoms typically manifest as necrotic brown or black lesions on the shoots and branches. As the infection progresses, these lesions can girdle the branches, leading to the sudden wilting and death of distal foliage. In early spring, infected buds may fail to open or produce stunted, withered shoots, which is a hallmark sign of the disease.

Environmental conditions play a crucial role in the disease cycle, with cool and wet weather being particularly favorable for the spread of Pseudomonas avellanae. Rain splashing is the primary vector for local dispersal, while the movement of contaminated pruning tools and infected nursery stock serves as the major pathway for long-distance transmission.

To control and prevent the spread of this pathogen, orchard managers should implement the following strategies:

• Sourcing only certified, disease-free plant material for new orchards.
• Systematic and frequent disinfection of all pruning equipment using appropriate bactericides.
• Prompt surgical removal and destruction of infected branches to reduce inoculum pressure.
• Strategic application of copper-based bactericides during dormant and pre-budburst stages.
• Continuous monitoring and strict quarantine protocols within the production area.