Cause The most significant canker disease of hazelnut is eastern filbert blight (EFB), caused by the fungus Anisogramma anomala, however, several other canker forming fungi have been found on EFB resistant cultivars. These fungi include Diplodia mutilla, Dothiorella omnivore, Valsa cf. eucalypti, and Diaporthe eres (also associated with kernel mold in the Caucasus region of Europe). Diplodia mutilla appeared particularly aggressive in repeated inoculation experiments while Dothiorella omnivore was very weak. Several of these are wound invaders gaining access to tissues through pruning wounds, sunburn, winter injury or herbicide injury. Phomopsis (Diaporthe) cankers have also been observed in BC.
Symptoms Observed symptoms in the field vary, but include dieback of branches, low nut production, small or poorly filled nuts, slow bud break, stunted leaves, poor growth, and presence of cankers on main trunks or branches that are not associated with EFB. Trees that were wound inoculated showed large brown-to-black lesions, lack of vigor and foliar chlorosis followed by defoliation.
- Control sunburn during summer using shields or white paint on trunks. Use plastic grow sleeves that are opaque and do not let in sunlight.
- Mulch around the base of newly planted trees with chipped, composed tree debris to reduce moisture stress.
- Use cultural practices that promote tree growth and vigor while minimizing injuries that expose wood.
- Cultivation and mowing equipment should not injure the roots, crown, or lower trunk.
- Make pruning cuts adjacent to, but not into, the supporting branch, and prune when branches are small to enhance callus formation and wound healing.
- Use techniques and equipment when herbicide and sucker spraying that minimize drift.
Chemical control There are no fungicides specifically labeled for these canker diseases although many of the chemicals labeled for EFB might be effective once the application timing is known. Some tree wound paints or treatments might be effective but there is no research on use of these materials on hazelnut.
Reference Wiman, N.G., Webber III, J.B., Wiseman, M., and Merlet, L. 2019. Identity and pathogenicity of some fungi associated with hazelnut (Corylus avellana L.) trunk cankers in Oregon. PloS one 14(10):e0223500.