Eastern filbert blight

Eastern filbert blight is a destructive fungal disease caused by the ascomycete Anisogramma anomala. It primarily infects hazelnut trees (Corylus spp.), leading to the formation of cankers that eventually girdle branches and trunks. If left unmanaged, the disease can devastate commercial hazelnut orchards by killing productive trees within a few years of infection.

The fungus has a complex two-year life cycle. During the first year, it colonizes the host tissue without showing external symptoms. In the second year, it produces visible stroma—black, erumpent, football-shaped structures—on the bark. These stromata release ascospores during wet weather, which are then disseminated by wind and splashing rain to infect new shoots, particularly targeting young, expanding buds.

Symptoms initially appear as small, longitudinal swellings on the branches. As the infection progresses, these swellings rupture the bark, revealing rows of black stroma. The foliage beyond the canker usually wilts and dies during the summer. Repeated infections lead to severe dieback, loss of vigor, and the eventual death of the main branches or the entire tree, depending on the severity of the colonization.

Environmental conditions, particularly moisture and temperature, dictate the spread of the pathogen. Spore discharge is highly correlated with rainfall and mild temperatures during the spring months. Since the infection occurs through young tissues, the period of bud burst is the most critical window for applying protective measures. Preventing the establishment of the fungus is essential, as once the disease has reached the main trunk, it is nearly impossible to save the tree.

Effective management requires an integrated pest management strategy to mitigate the risk of infection. Key actions include:

• Regular scouting and pruning of diseased wood, ideally 1-2 feet below the visible canker.
• Planting resistant hazelnut cultivars to reduce disease susceptibility.
• Applying preventive copper-based fungicides or other approved protectants during the period of bud development.
• Ensuring proper orchard sanitation by removing and burning infected pruning material to minimize the local spore load.