Dr. Dave Clement, University of Maryland Extension Plant Pathologist, explains two common diseases of this popular evergreen tree.
Colorado blue spruce trees, although not native or adapted to Maryland, are commonly planted in landscapes for their attractive color and shape. There are, however, two plant diseases that commonly infect and disfigure them. Both diseases also can occur simultaneously and progressively speed up the decline of this popular tree.
Needle Cast or Needle Blight
The most common needle problem of blue spruce in Maryland is a fungal disease caused by Rhizosphaeria kalkoffii.
- On the lower branches, yellowing of first-year needles in mid-summer on 8-15 year-old trees.
- Then the needles turn brown, or sometimes purplish brown, before they defoliate through the late summer into fall.
- These symptoms will continue to spread upward and around the tree. Branches will decline and die after 3-4 years of successive defoliation.
- Tiny black spheres (the fungal spore structures) can be seen along the bottom of the needles with a hand lens or microscope.
Dieback or Cytospora Canker
The most common dieback disease of blue spruce in Maryland is caused by the fungal pathogen Leucostoma kunzei.
- Off-color to brown needles, first on lower branches of 10-15 year-old trees in spring through early summer, progressing to entire branches.
- The needles can remain attached during the summer until they defoliate over the winter season leaving bare twigs and stems.
- The ornamental value of infected landscape trees will decline after several years of defoliation and symptom progression up the tree.
- The dark fungal fruiting bodies may be hard to find since the diseased bark is stuck together by the crystallized resin.
Infection starts in the spring on wounds caused by pruning cuts, insects, hail damage, or cracks caused by ice, or snow load. The disease causes large amounts of resin flow that appear as white crusty sap streaks on the bark. The infection period can extend from spring through fall depending on rainfall. Drought stressed trees are more vulnerable to this disease.
Practical management of both of these diseases is difficult because the infection period can extend from spring through fall depending on rainfall. Diseased branches can also serve as sources of infective spores for many years after infection and help intensify disease progression. Therefore, fungicide sprays are impractical for most homeowner trees. Severely diseased trees should be removed and replaced with better adapted conifers for the mid-Atlantic region.
Alternatives to Blue Spruce
If you are looking for a nice evergreen tree for your landscape, consider any of the following alternatives to blue spruce. These have fewer disease problems. Be sure to research the growing requirements (e.g., winter hardiness, etc.) for these trees, to make sure they are appropriate for your location in Maryland.
- Arizona cypress (Cupressus arizonica ‘Blue Ice’)
- Oriental spruce (Picea orientalis)
- Himalayan cedar (Cedrus deodara ‘Karl Fuchs’)
- Serbian spruce (Picea omorika)
- Eastern red-cedar, Juniperus virginiana ‘Grey Owl’ (with berries) or ‘Manhattan Blue’ (without berries).
By Dr. Dave Clement, Principal Agent, University of Maryland Extension, Home & Garden Information Center.
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I’d have to respectfully disagree about Serbian Spruce! They seem just as susceptible to needle cast/blight. At least all the ones I’ve been scouting, anyway. Norway Spruce, although not blue, would be a better choice.
@hortlady2017 Thanks for weighing in about what you’ve seen with Serbian spruces. Norway spruce is indeed a nice tree, but it is now found to be invasive in some areas, unfortunately.
Arizona cypress?! Although it happens to be one of my favorites, it is completely different from Colorado blue spruce. So are the Eastern red cedars. Are the blue Eastern red cedars as blue as the blue spruce is? I have only seen green here.
Our blue spruce are largely intact still but seeing increasing decay on the interior of the tree and lower branches. When do you recommend cutting the trees down completely? Will this spread to other types of pines on our property that are not spruce? Thank you.
It’s really up to you. Some people will leave mature blue spruces up even when they look thin. When you feel ready to replace your tree, then it’s time to cut. Cytospora canker does also affect Douglas and balsam firs, eastern hemlocks, larches, red pines, eastern white and Himalayan white pines, but it is less common in those species. https://extension.umd.edu/hgic/cytospora-canker-spruce
So I have about 50 Spruce trees that are dying from the bottom up. What I am gathering from this article is that I need to cut them all down, and there is nothing I can do to ‘save’ them. Is that a fair statement? My trees are MASSIVE, and cutting them down is going to cost a fortune. I guess what I am looking for is a few alternatives.
If your going to cut them down, try putting horse manure under the trees for a few years and see if that brings them back to life. The tree needs help with its immunity and the nutrients and acidity will help.
My problem is like that of Rob (July 31, 2019). My trees were well-sheared, 5-feet tall, 8 to 10-year old trees when I planted them 34 years ago. In your reply to Rob were you suggesting that “putting horse manure under the trees for a few years” may actually rejuvenate the lower part of the trees?!! … or is this wishful thinking? If I cut down the “really bad actor” trees is it reasonable to expect that a “new,” 8 to10-year old tree planted in the same location as an old one, but removed, say, 5 feet from the old stump will “live the same kind of (excellent) life” as the old 42-44 year-old tree that it replaces?
So I have plenty of horse manure, problem is it is located at my parents house, and I cant imagine hauling truck loads of horse manure for 50 trees. Although if it saves me from cutting down all these massive trees, I am willing to try anything.
Wouldn’t it be better to plant a shrub/tree that is native to Maryland?
Yes, for selecting Maryland native trees and shrubs that would make suitable replacements, I recommend using the Chesapeake Bay Native Plant Center. http://www.nativeplantcenter.net/.