| Disease |
Symptoms |
Pathogen/Cause |
Management |
| Cytospora Canker |
Cankers, sunken dead areas of bark and underlying
wood, form on the lower branches of the trees girdling
small branches in 1 or 2 years and large branches after several
years. Resin flows out of the cankers and may drip down on lower
branches. Scattered lower branches die. Branch death progresses
up the tree. Blue, white, red, black, Engelmann, and Norway
spruces are all susceptible to this disease. |
Leucostoma kunzei
(Cytospora) |
Since the fungus
readily infects wounded tissue but remains latent in the
tree without causing symptoms until the tree is drought stressed,
fungicide sprays can not be effectively timed to prevent this
disease. Select the planting site carefully, avoiding drought
prone sites. Anticipate the future needs of the mature tree
and consider whether the site has the potential of supplying
the water requirements of a 50- to 60-foot tall specimen. Prune
infected branches. |
| Rhizosphaera needlecast |
Year-old needles turn lavender in color and have
tiny, black, fungal fruiting structures in rows on either side
of the midvein on the underside of the needle. Large bare areas
develop on the tree as needles fall. Blue and Engelmann spruce
are highly susceptible. White spruce are somewhat susceptible.
Norway spruce are relatively resistant. |
Rhizosphaera |
Space trees and provide good weed control to
insure free air circulation around the tree. Apply chlorothalonil
when new shoots are 1 1/2 inches long and again 3 weeks later
to protect young needles from infections that occur in May through
June. Some locations have an additional infection period in
September and October. |
| Needle Rust |
Year-old needles are cast after turning rust
colored in the spring. Blue spruce is very susceptible. Black,
Engelmann, red, Sitka, and white spruces are also susceptible.
This rust does not require an alternate host. |
Chrysomyxa weirii |
Notify the Bureau of Plant Industry immediately
to obtain a positive diagnosis Destroy infected trees. To protect
trees not yet affected, apply chlorothalonil first when 10 percent
of the tree is in bud break, again 1 week later, and again 3
weeks after the first spray. |
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