of Rhode Island GreenShare Factsheets
Canker of Spruce
canker of spruce is the most common and damaging disease of spruces
in the East. The causal agent, Leucostoma kunzei, attacks
black spruce, Colorado blue spruce, Norway spruce, white spruce,
Douglas fir, balsam fir, eastern hemlock, eastern larch, European
larch, Japanese larch and eastern white pine.
on infected spruce branches turn brown in spring or early summer.
Copious amounts of white sap exude from cankers on the affected
branches and run down the tree. White patches of dry resin on the
trunk are characteristic of this disease. Brown needles persist
throughout much of the growing season, but drop in winter, leaving
bare branches. The infection tends to move up through the tree,
as older branches are more susceptible than younger ones. This disease
affects mature trees, commonly 15-25 years old and 20 to 40 feet
high. Symptoms of cytospora canker are the same on other conifers,
with cankers produced on branches and trunks of balsam fir, Douglas
fir, eastern larch and, rarely, hemlock. Sap production, however,
is less noticeable in these conifers.
a thin slice of bark in the area where healthy and infected tissue
meet will reveal tiny, black fruiting structures. Yellow to orange
masses of spores ooze from these structures in tiny tendrils during
rainy spring and summer weather and are disseminated by splashing
water, wind-driven rain, pruning, and possibly by insects and birds.
The fungus generally becomes established in fresh wounds, and overwinters
on bark and in cankers.
There are no effective chemicals to control this disease.
Avoid wounding branches.
Early detection and removal of infected branches will
reduce the probability of more extensive disease development.
Prune out infected branches close to the trunk during dry weather or during
winter to reduce disease transmission, disinfecting tools between
cuts. Burn infected branches to prevent the release of spores.
Trees suffering from drought stress and low fertility
are more susceptible to this disease, so provide adequate water
and fertilizer. Water the entire root zone deeply- 1 1/2 times farther
than the branches extend.
Control insects and mites--especially spruce gall adelgids
and spider mites--to prevent spore transmission.
Picea omorika is resistant to this disease.
Avoid planting Colorado blue spruce, as it is extremely susceptible
to cytospora canker.
from the Ohio State University Extension, 1999
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
of Rhode Island Cooperative Extension provides equal program