In This Section | Notes
on Nut Diseases |
| Author: | OMAFRA Staff |
|---|---|
| Creation Date: | 17 May 2006 |
| Last Reviewed: | 17 May 2006 |
Eastern filbert blight is a serious disease of commercial hazelnuts of European origin and is caused by the fungus Anisogramma anomala. This blight fungus is native to eastern North America and occurs naturally on native wild hazelnut but does not cause injury on these wild hosts.
Black raised fungal bodies called stromata are produced in relatively straight rows that run lengthwise along the branch in cankers. Cankers are dead, sunken tissues along a branch, which grow larger each year. If the canker eventually encircles a branch or trunk, the wood beyond the canker will die. Leaves on dead branches dry up and turn brown but remain attached. Plant vigour and productivity decline significantly when trees are infected with this fungus and result in an economically unproductive orchard. Mortality of sensitive cultivars usually occurs within five to ten years of planting new trees without management intervention.
In spring, spores are released from mature cankers in infected hazelnut trees. Wind-driven rain spreads spores to young developing shoots. New infections occur on sensitive new leaf and stem tissue. No symptoms are visible for approximately 15 months. During the second summer after infection, the fungus starts to produce the spore-producing structures that are used to identify infection by eastern filbert blight. These structures will release spores the next spring.
In
hazelnut regions where eastern filbert blight is a new invasive organism that
affects susceptible European hazelnuts, management of this disease is costly.
Research is underway to develop new hazelnut cultivars that are immune to eastern
filbert blight infections. Immunity to eastern filbert blight in primary cultivars
and in pollinating cultivars may not be available for 10 to 20 years.
In
susceptible orchards, scout during the summer for symptoms of filbert blight disease.
The first infected branches often appear in the upper canopy of trees. Watch for
dead brown leaves clinging to twigs, which can help identify infected branches.
Prune out diseased cankers and dead branches cutting two to three feet below the
site of infection. Burn or bury diseased wood to prevent spores from spreading
back into the orchard.
Apply preventative sprays from bud swell to just after bud break and use copper oxychloride to prevent new infections of eastern filbert blight. Two or more fungicide applications are generally required to achieve some control of eastern filbert blight -infections.
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