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Plantwise Technical Factsheet

eastern filbert blight (Anisogramma anomala)

Host plants / species affected
Corylus americana (American hazel)
Corylus avellana (hazel)
Corylus maxima (filbert)
List of symptoms/signs
Leaves  -  abnormal colours
Stems  -  canker on woody stem
Stems  -  dieback
Stems  -  discoloration of bark
Stems  -  stunting or rosetting
Whole plant  -  plant dead; dieback
The first symptoms appear 12-16 months after infection, as brownish sunken cankers developing on branches and twigs. Cankers expand in all directions. They may coalesce when growing. Stromata then become visible and some branches may die. The formation of mature perithecia in the stromata takes up to 25-27 months. Young seedlings can be stunted, show abnormal stems and symptoms of interveinal chlorosis or necrosis on leaves. Cambium death around the canker results in a sunken appearance as the surrounding cambium continues to grow.
Prevention and control
Eradication was attempted but was not feasible as wild or volunteer Corylus plants in adjacent woodland provided an unmanageable reservoir of inoculum. Sanitation measures include destruction of infested wood, but are of little value because of the length of the latent period in the life cycle of the fungus. Chemical control has been applied, but was not very successful as the biology of the fungus was not well known (Pinkerton et al., 1992). Experiments have only recently been carried out to determine efficient chemical treatments. Johnson et al. (1993) found that chlorothalonil, flusilazole and fenarimol are potentially valuable components of a programme for control of A. anomala. Four or five applications during the period of potential infection can completely control the disease. However, such a programme may not be economically feasible for all growers. Genetic resistance is the only viable disease control strategy. Cultivars range in susceptibility from highly susceptible to immune. Corylus cornuta var. cornuta, C. cornuta var. california, C. heterophylla and C. sieboldiana were highly resistant, as were most C. americana genotypes and one C. colurna clone (Coyne et al., 1998). Breeding programmes are being conducted. Some European cultivars showed high susceptibility to the disease (Pinkerton et al., 1993).

Phytosanitary measures

A. anomala can be introduced with planting material of hazel. In the USA, spread of the disease to the West is thought to have been due to the importation of infected C. avellana nursery stock or of wild C. americana seedlings from the Eastern regions. Corylus planting material should be imported only from areas free from A. anomala.
In the USA, this fungus had no economic importance as long as it remained confined to the east of the country, on wild species of Corylus. Since 1986, it has spread to Oregon in the Willamette Valley, where 98% of American commercial hazelnuts are produced (Mehlenbacher et al., 1994). Nearly all orchards within a 10 km radius of the initial site of disease have been destroyed, and the disease has continued to spread to the southwest. Infected orchards are rendered unproductive in 4-8 years. All cultivars grown commercially in this area are susceptible.
Related treatment support
External factsheets
Plant Health Australia Factsheets, Plant Health Australia, English language
British Columbia Ministry of Agriculture Factsheets, Government of British Columbia, 2009, English language
Cornell University Factsheets, Cornell University Plant Pathology Department, 2013, English language
PlantVillage disease guide, PlantVillage, English language
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