Notes on Nut Diseases
Eastern filbert blight
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.
Identification
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.
Period of activity
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.
Management
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.
Learn more...
