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Spruce diseases, disorders
appearing in landscape
By
Aimee Nielson
 LEXINGTON,
Ky., (Dec. 19, 2007) – Kentucky gardeners may notice diseased
and declining spruce trees in the Kentucky landscape. The
effected trees are showing yellowing, browning and shedding of
needles, twig and branch dieback and even limb death.
“There are many different causes for spruce problems, and many
of the problems are made worse by, or are connected to,
drought,” said John Hartman, University of Kentucky College of
Agriculture extension plant pathologist. “Blue spruce trees are
especially affected.”
Hartman said spruce trees usually retain their needles for
several years, and normal needle drop is hardly noticeable
without careful examination of the inner branches, where a few
scattered needles may turn yellow and drop in late spring or
early summer of their third year. But when a drought occurs,
especially monumental drought as in 2007, needle drop could be
earlier and more severe.
“Cytospora canker, a fungal disease, is commonly found on
Kentucky spruce trees,” Hartman explained. “It’s most noticeable
on trees older than 20 years. It is often first noticed on the
lower branches with canker formation accompanied by white resin
appearing on the infected branches or trunk. As the canker
enlarges, the branch is girded and killed. Needles on effected
branches can appear purple at first, and then turn brown as they
die. Trees growing under stressful urban conditions, especially
drought, are most vulnerable to Cytospora canker. Wounding,
mechanical injury, construction damage and insect damage may
also contribute to the disease.”
Drought alone can cause sporadic needle yellowing and loss,
followed by tree decline. If spruce trees are planted in the
wrong place, as they grow, they may not have adequate space for
optimal root development. Inadequate rooting space in an urban
environment results in drought conditions for the tree, even
when there is adequate rainfall, Hartman said.
“Be aware that spruce trees are not generally native to Kentucky
and they may grow better elsewhere,” he added.
Aside from drought, other factors can cause poor health in
spruce trees including fungal needle cast diseases and spider
mites. Spruce health is enhanced by good growing conditions.
Hartman recommends providing one inch of water per week during
times of drought, applying water over the root zone and avoiding
getting the foliage wet.
“Mulch under the trees to retain moisture,” Hartman continued.
“Grass competes very well and can actually contribute to spruce
tree water stress. Prune out diseased and dying branches under
dry conditions and take them away for burning or burial.”
Hartman concluded by saying that pruning tools need to be
sterilized with 70 percent alcohol between cuts. A diagnosis of
needle cast disease may warrant fungicide treatment. |
Contact: John Hartman, 859-257-7445, ext. 80720
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The UK College
of Agriculture, through its land-grant mission, reaches across
the commonwealth with teaching, research and extension
to enhance the lives of Kentuckians. |
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