Insect
and Disease Fact Sheet Compliments of New Century
1-877-79TREES
Cytospora Canker of Spruce
Cytospora canker on spruce
twig.
The
most important disease of spruce
in landscape plantings in Ohio is Cytospora canker.
This disease is caused by a fungus and is frequently found on Norway spruce and
Colorado blue spruce and its cultivars. White spruce is also susceptible and
there are a few reports on Serbian spruce. In addition to the spruces Cytospora canker is sometimes found associated with Douglas
fir, hemlocks, larches, and balsam fir.
Symptoms
Dying
of a lower branch with subsequent needle browning is usually the first symptom.
The brown needles may remain on the branches or they may fall off. As the disease progresses over
several years, higher branches show damage. The actual cankers are often first
seen at the base of branches
near the main trunk of the
tree. On the more susceptible species (Norway spruce), trunk cankers develop
which may result in girdling and death of
the tree.
The
bark of the cankered areas is not visibly different in color, nor does it
become sunken as in cankers on many deciduous trees. However, resin flow is
usually associated with Cytospota canker and the
white patches of dried resin are quite conspicuous on the bark. Resin flow can,
however, be associated with any injury to branch tissue.
Cankers
often cannot be located without cutting into the bark. Removal of the outer
bark from cankers reveals brown, dead areas of the inner bark and cambium:
Within the cankered areas, a careful search using a magnifying hand lens will
often reveal black pinhead sized structures that produce the spores of the
pathogen. Careful removal of layers of bark makes these structures even more
visible. During wet weather, yellow to orange colored masses of spores oozing
out of these black structures
in tiny tendrils can be observed. Sometimes these tendrils or gelatinous spore
masses are visible to the unaided eye.
Causal Fungus
Cytospora canker of spruce is caused by the.fungus,
Cytospora kunzei var. piceae (also reported as Valsa kunzei var.piceae). The spores
(conidia) described above are readily disseminated by splashing water,
wind-driven rain, by man during pruning, and also very likely by insects and
birds. The fungus generally becomes established through wounds.
Disease Management
Cytospora canker is more common on trees over 15 years old. This disease is more
prevalent on trees of low vigor. Those trees with shallow roots, weakened by
drought, low fertility, mechanical injury, or insect damage; and trees growing
in an unfavorable site are more susceptible to Cytospora
canker. The following practices lessen the likelihood of this disease.
Cytospora canker occurring on lower
branches of blue spruce tree.
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1. Avoid bark and stem injuries. 2. Control insects and mites; especially spruce
gall adelgids and spider mites. 3. Fertilize according to horticulturists
recommendations. 4. Water during extended dry periods. Water
thoroughly so that soil is moistened 18 to 24 inches deep. A root-irrigator
may-be needed to accomplish this. 5.
Follow accepted pruning practices. 6.
Vertically mulch to relieve soil compaction, poor aeration, and inadequate
water penetration. Once
established, the following may aid-in-suppressing disease development.
Remember that affected branches cannot be saved. |
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Prune
and remove or destroy affected branches. To lessen the spread of thy fungus,
prune only when the trees are dry. Pruning tools should be disinfested with
70% alcohol between cuts. It will generally be necessary to prune back to the
main trunk. No effective chemical control measures are available. |
Effects of Cytospora canker on spruce tree. Lower limbs removed. |
Information obtained through the Ohio State Extension Factsheet HYG-3033-96
Insect
and Disease Fact Sheet Compliments of New Century
1-877-79TREES