Eastern Filbert Blight is a disease caused by the fungus – Anisogramma anomola and is native to the northeastern United States and eastern Canada (although it has appeared in British Columbia, as early as 2001). Hazelnuts native to this region (Corylus americana) have proven to be more resistant to the disease (some are even immune) than the imported European hazelnuts (Corylus avellana). For Harry Lauder’s Walking Stick, a contorted hazelnut (Corylus avellana ‘Contorta’) the disease is lethal.

Symptoms:
Often one of the first symptoms homeowners report are droopier than normal leaves, accompanied by the dieback of twigs and branches. Dead leaves may remain attached to the branch, this often a good indicator of the disease. Upon closer inspection elongated (football shaped), dark brown to black spore producing bodies called stromata can be found, appearing in relatively straight rows lengthwise along the branch.

Life Cycle:

In the spring, about the time the hazelnuts are at bud-break, the stromata are forcibly ejected and released in a sticky, white ooze in wet weather (Pacific Northwest Extension (n.d.)). These fungal spores (ascospores) are carried by rain and splashing water droplets driven by wind, to new areas of the branch, new branches and potentially nearby trees of the same species. Infection takes place from bud break through shoot elongation. Once spores have adhered to the stem surface, they penetrate epidermal cells directly (Cornell University (n.d.)). Wounding is not required.

Rows of stromata are formed within cankers (dead areas on the bark or stem, often sunken or raised), approximately 12 to 18 months after the area has been infected. “Ascospores begin to mature in fall as the rainy season begins. Several hours of continuous rain are needed for ascospore release. Ascospores are shed all winter but cannot infect hazelnuts until spring” ((Pacific Northwest Extension (n.d.)). The cankers continue to grow, eventually girdling the branch, resulting in branch dieback. (Note: According the Plant Disease Diagnostic Clinic, at Cornell University cankers can grow in size anywhere from a few centimeters up to 1 meter annually.)

Control:

• Prune out and destroy infected wood well below the cankers (1 to 3 feet back) (Siva Sabaratnam (2018)). This must be done before bud break in the spring. The branches must be pruned back this far to ensure the complete removal of all fungal spores (which are always ahead of the visual signs of the disease). Like a cancer any remaining spores can continue to grow and kill branches.
• Plant resistant cultivars 
• Fungal sprays: apply a fungicide four times per season to adequately protect your trees, starting at budbreak. Be sure to thoroughly cover all of the branches.
  1. Serenade Garden: an organic, broad spectrum bio-fungicide used for the control or suppression of the disease. It inhibits the growth of the bacteria on the surface of the plant. It needs to be applied early in the disease, preferably before leaves are infected.
  2. Organocide Plant Doctor: is an natural, earth friendly, broad spectrum, systemic fungicide. It works its way through the entire plant to prevent disease and attack existing disease. Even though it is labeled a fungicide the manufacturer claims it is effective for fire blight.
  3. Copper Oxychloride 50 or Copper Spray to prevent new infections. Copper is generally acceptable for organic production.
  4. Bonide Fung-onil Multi Purpose Fungicide
  5. Flint 50 WG (50% trifloxystrobin)

Note: For Ontario residents check the Ontario Ministry of the Environment for an up-to-date list of permitted pesticides. https://www.ontario.ca/page/pesticides-home-lawns-and-gardens  

Look-a-like Diseases: 
According to Jay W. Pscheidt, Extension Plant Pathologist at the Oregon State University, Eastern Filbert Blight resembles another fungal disease caused by the fungus Eutypella cerviculata. Eutypellaproduces similar spore producing structures, however, they are said to be smaller in size and produced on dead wood. To properly identify this fungus, take a small knife and scrap away the surface layers of the diseased area. If the disease is the result of the fungus Eutypella cerviculata  rather than EFB you will find black rings around the stromata.

Photo credits: all photos have been taken by the author.

References:

Pacific Northwest Extension (n.d.), ‘Hazelnut (Corylus avellana)-Eastern Filbert Blight’; Retrieved on Jan.16, 2021 from: https://pnwhandbooks.org/plantdisease/host-disease/hazelnut-corylus-avellana-eastern-filbert-blight

Cornell University (n.d.), The Plant Disease Diagnostic Clinic, ‘Eastern Filbert Blight: Anisogramma anomola’, Retrieved on Jan. 16, 2021; http://plantclinic.cornell.edu/factsheets/efilbertblight.pdf

Siva Sabaratnam (2018), (Plant Pathologist, British Columbia Ministry of Agriculture), ‘Eastern Filbert Blight’ Retrieved on Jan. 16, 2021 from: https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/agriculture-and-seafood/animal-and-crops/plant-health/phu-easternfilbertblightss.pdf

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