Eastern filbert blight

Eastern filbert blight is a destructive fungal disease caused by the ascomycete Anisogramma anomala. This pathogen is a significant threat to hazelnut (Corylus spp.) production globally. As a canker disease, it invades the bark and cambium of the tree, leading to the formation of characteristic stromatic cankers that eventually girdle branches and trunks, resulting in systemic dieback.

The primary hosts of this pathogen are various hazelnut species and cultivars. The fungus attacks the tree by colonizing the succulent tissues of young shoots and buds. If left unmanaged, the blight can decimate entire orchards, as the fungus continuously produces new spores that colonize adjacent healthy wood, leading to the eventual collapse of the plant's vascular system.

Symptoms of the disease are distinct and often progressive.

• Emergence of rows of black, pimple-like fungal fruiting bodies on the bark.
• Deep longitudinal cracking of the bark in the affected areas.
• Yellowing of leaves and sudden wilting of branches during the growing season.
• Growth of elliptical or irregular cankers along the stems.
• Gradual death of the entire canopy above the infection site.

The disease development is highly dependent on environmental conditions, particularly rainfall and humidity, which trigger spore release from late winter through early summer. The incubation period is relatively long, often taking up to 18–24 months before the first visible symptoms of the stroma appear. Spores are primarily disseminated by splashing rain and wind currents, making wet springs particularly hazardous for new infections.

Management strategies focus on a combination of cultural and chemical control. Growers should prioritize the selection of resistant cultivars where possible and ensure rigorous sanitation by pruning and destroying infected branches at least 1–2 feet below the visible canker. Protective fungicide applications are necessary during the bud break and active growth periods to prevent new infections. Consistent orchard monitoring and the removal of wild hazelnut hosts in the vicinity are essential for long-term disease suppression.