Tree Diseases of the Blue Atlas Cedar
Blue atlas cedar, or Cedrus atlantica, is an evergreen with bluish-green, light green or blue foliage. The tree has an irregular, open pyramidal form and reaches a mature height of 40 to 60 feet. The branches start to droop with age and require pruning to keep in shape.
While the tree is generally free from diseases and pests, there are a few it may suffer from.
The deodar weevil or Pissodes nemorensis Germar, is also known as the eastern pine weevil. This weevil commonly infests atlas and deodar cedar, cedar of Lebanon and a variety of southern pines. The adult weevils and larvae destroy the terminal and lateral branches and girdle small branches in younger trees. The damage causes canker fungus on branches and these tree wounds make trees highly susceptible to infections. The 1/4 inch deodar weevils are rusty red to grey brown in colour and have long snouts. The larvae are legless with reddish brown heads. If not controlled they can kill the smaller trees entirely. Deodar weevils can be controlled with the use of recommended tree insecticides and by ensuring that the trees are properly watered and fertilised.
Black scale, Saissetia oleae, is among the most damaging of tree pests. Though very common in citrus trees, black scale frequently invades a variety of other trees and shrubs including the blue atlas cedar. The adult females are dome shaped, black or dark brown and 1/3 inch in diameter. During May and June the females lay hundreds of white to reddish orange eggs under their hard shelled bodies. The hatching scales are light brown in colour and start to feed on the leaves of the infested tree. The colour of the scales gets darker as they lay eggs and their ridged bodies are very hard to discern on barks and branches. If scales are limited to certain areas of the tree, it is recommended to prune those branches heavily. Use recommended insecticides to control infestations.
Tip blight is also called die back and occurs mostly on trees that are growing in stressful conditions like drought, heavy shade, or when the tree is competing with other trees close by. Tip blight is very common in the blue atlas cedar during humid or wet weather. In wet seasons it is not uncommon to see the branches of the entire tree show browning tips. Symptoms of tip blight include stunted new growth and browning of the needles. The lower branches are the first to be affected. Tip blight is not easy to control especially in older trees. The best remedy is to prune back the infected twigs, needles and cones to the healthy tissue as soon as tip blight is suspected. Prune when branches are dry since the spores can spread on wet branches. Fungicides may be tried in severe cases.
- Department of Agriculture Forest Service: Blue Atlas Cedar
- Forests Pests: Deodar Weevil
- “Pests of Landscape Trees and Shrubs;” Steve H. Dreistadt, Jack Kelly Clark; 2004
- “Pirone’s Tree Care;” John Richard Hartman, Thomas P. Pirone, T. P. Pirone, Mary Ann Sall, Pascal Pompey Pirone; 2000
- "New York Gardener's Guide;" Ralph Snodsmith; 2004