Hazel catkin blight

Ciboria coryli is a fungal pathogen responsible for a disease commonly known as hazel catkin blight. This specialized fungus primarily targets the reproductive structures of the hazel tree, often significantly impacting the potential yield of commercial hazelnut orchards by disrupting the pollination process.

The primary host for this pathogen is the common hazel (Corylus avellana) and various hazelnut cultivars. While it primarily affects the male catkins, the fungus can also impact the developing nut clusters, leading to stunted growth or complete loss of the individual fruit, which directly affects the economic viability of the hazelnut harvest.

Symptoms typically appear in late winter and early spring. Infected catkins become dark, brittle, and shriveled, failing to release pollen effectively. In severe cases, the infection may spread to the nut husks, resulting in necrosis and rotting. During humid conditions, microscopic fruiting bodies of the fungus may emerge from the infected tissue to facilitate further spread.

The development and spread of Ciboria coryli are heavily influenced by environmental factors, particularly moisture and temperature during the early spring months. The fungus overwinters in mummified catkins and fruit remnants lying on the ground, releasing spores that are easily dispersed by wind and splashing rain when the hazel trees are most vulnerable.

Management strategies focus on sanitation and preventive chemical treatments. Orchard hygiene is paramount: removing and destroying infected plant debris reduces the primary inoculum source for the following season. Proper pruning to improve airflow within the canopy and the application of suitable fungicides during the dormant to early-bud stages are essential components of an integrated pest management program.