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.