Darkened blue spruce needles are infected with needlecast fungus. - Putnam Sentinel
Darkened blue spruce needles are infected with needlecast fungus.

PUTNAM COUNTY — One of the most beautiful and popular conifers planted in landscapes across Putnam County is the Colorado blue spruce. The nursery industry has developed many different forms and color variations of the blue spruce, making it widely available across Ohio as specimen trees and for use in windbreaks. It also happens to be the landscape plant that we receive the most questions on here in the Extension office.

The Colorado blue spruce (Picea pungens) is native to the arid regions of the Rocky Mountains in the western United States. While it prefers moist but well-drained, acidic soils – the blue spruce adapts well to soil conditions found across Ohio. The blue spruce has a moderate growth rate and when mature, trees can reach 50 feet tall by 25 feet wide.

In recent years, a decline in the health of blue spruce trees has been noted in Ohio, Michigan, and surrounding states. Spruce decline is generally first noticed when needles turn brown and tree limbs begin to die back. These symptoms are often caused by diseases that affect the branches and needles of stressed trees.

Symptoms of these diseases generally appear on mature trees that are quite large in the landscape. Trees that are planted closely together with overlapping branches are more prone to disease spread. Trees also differ in their susceptibility – and homeowners might have one perfectly healthy tree next to one or more that are diseased.

The two most prevalent diseases affecting Colorado blue spruce in Ohio are a needlecast fungus known as Rhizospaera and the fungus Cytospora that causes stem cankers. Unfortunately, our wet springs and humid summers provide perfect conditions for these diseases to take hold and infect blue spruce in Ohio.

Needlecast fungi infect new foliage in the spring but symptoms do not show up until the following year. New growth appears healthy while inner needles on a branch turn shades of purple and brown and eventually drop from the branches. This fungus can be easily identified by the spores found on infected needles. Fungicides can be effective in controlling this disease on new growth but must be applied over several years.

Cankers caused by Cytospora infect tree branches causing sunken areas that ooze resin. These cankers cut off the flow of water and nutrients to the branch causing it to die. The best remedy for stem cankers is to remove the branches once cankers are found and to provide conditions for optimal tree growth.

What can homeowners do? When selecting a site to plant Colorado blue spruce, make sure trees will be planted in a location that has well-drained soil and receives full sun. Properly space trees so there is ample air flow between trees as they increase in size over time. While trees may be small at planting, realize that mature blue spruce trees can span 25 feet in width.

Homeowners should also monitor tree health over time. Carefully inspect branches and needles. If you suspect disease or insect infestations, contact a certified arborist or tree care company, or the local Extension office. A nice publication on pest and cultural issues associated with spruce trees from the University of Illinois can be found here: https://web.extension.illinois. edu/plantclinic/downloads/ Plant%20Clinic%20 Report%20Spruce.pdf

For additional information, please contact the Putnam County Extension office at 419-523-6294, at scheckelhoff.11@osu.edu, or stop in at 1206 East Second Street in Ottawa. You can also find us on Facebook by searching for OSU Extension Putnam County.