Hazelnut asteroma

Systematic position and type of pathogen: Asteroma coryli belongs to the kingdom Fungi, phylum Ascomycota, and class Dothideomycetes. It is an obligate or facultative phytopathogenic fungus that specifically targets the foliage of hazel trees, leading to the development of necrotic spots on the leaves.

Diseases and host plants: The primary host for this fungus is common hazel (Corylus avellana) and other species within the Corylus genus. The pathogen causes a condition known as leaf spot, which is frequently observed in commercial orchards and wild hazel forests, affecting both ornamental and nut-producing plants.

Biology and life cycle: The fungus overwinters primarily in the form of pycnidia located on infected fallen leaves. In the spring, when temperatures rise and rainfall occurs, these pycnidia release conidia that are dispersed by wind and water droplets to infect newly emerged leaves, starting the annual infection cycle.

Conditions for development and harmfulness: The development of the fungus is favored by high relative humidity, frequent precipitation, and poor air circulation within the canopy. The harmfulness of the disease is expressed through premature leaf yellowing and shedding, which leads to reduced photosynthetic capacity, overall tree stress, and a measurable loss in nut yield and quality.

Protection and control measures: Controlling the spread of Asteroma coryli requires a combination of sanitation and chemical treatments:

• Sanitary disposal of fallen leaves to eliminate the primary inoculum source.
• Pruning the canopy to ensure adequate light penetration and air movement, reducing the humidity around leaves.
• Application of broad-spectrum or systemic fungicides during the early leaf expansion phase.
• Maintaining plant vigor through balanced fertilization to help the trees withstand seasonal pathogen pressure.