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Diseases of Blue Atlas Cedar

By Aileen Clarkson ; Updated September 21, 2017

The Atlas Mountains of Algeria and Morocco were the original home of the Blue Atlas cedar (Cedrus atlantica). This stately evergreen has bluish-green or light green needles in an irregular, open pyramid form. A fast grower when it is young, the Blue Atlas eventually reaches 60 feet tall and grows up to 40 feet wide. While it is drought tolerant and easy to grow, a few diseases can affect this member of the Pinaeceae family.

Diplodia tip blight

Diplodia tip blight first appears on the Blue Atlas cedar as dead, brown needles at the tips of its branches. At the base of the brown needles, you also may see tiny, black fruiting bodies (pycnidia). Infection can weaken or kill your tree if it spreads to the terminal buds. Old or weak trees are most susceptible to diplodia. Water thoroughly once a week during extended dry periods, fertilize every spring, and remove infected twigs when the tree is dry to avoid spreading spores. When pruning, swab the blades of your trimmer between each cut with a solution of 70 percent rubbing alcohol. Destroy infected parts, and do not compost.

Root rot

The Blue Atlas cedar prefers slightly acidic, well-drained loamy soil. Waterlogged soil can lead to root rot caused by the water mold Phytophthora. Trees can be infected for years before showing symptoms. According to Bartlett Tree Experts, symptoms include branch dieback, small shoots and leaves, thinning crown, chlorosis and eventually death. When planting your tree, amend the soil with compost or peat moss to ensure it drains well.

Cold damage

Blue Atlas cedar is hardy in USDA zones 7 through 10. According to treehelp.com, this tree is sometimes sold in marginal climates, which can lead to cold damage. Cold damage symptoms may include dead bark tissue, frost cracks and brown needles. Extensive cold damage can kill the tree's heartwood.


About the Author


Aileen Clarkson has been an award-winning editor and reporter for more than 20 years, earning three awards from the Society of Professional Journalists. She has worked for several newspapers, including "The Washington Post" and "The Charlotte Observer." Clarkson earned a Bachelor of Arts in journalism from the University of Florida.