Our Local Cedars Are Under Attack

by Gyvel Young Witzel ©2008

Our cedars are dying! Recent observations around the Hill Country area have confirmed the “browning” of the Ashe Juniper, locally known as “cedar.” In fact, large stands of naked cedars have been sighted. And—old growth cedars used as ornamental trees have also been affected.

The cedar tree is deemed by many to be a nuisance with highly invasive properties. It’s blamed for hogging ground water and taking needed resources away from other trees such as oak, Cypress, and Mountain Laurel.

In fact, it provides natural diversity to the landscape and habitat for many birds and animals. It’s a necessity to the endangered golden-cheeked warbler, who requires cedar bark to build its nests. For man, the tree is useful as a privacy screen, wind break, and for erosion control.

Although our native cedars trees are highly pest and disease resistant, they can be attacked by blight. The first type of “twig blight” is caused by the Phomopsis and Kabatina fungi. These infect new growth on the branches and then work their way to the tree center. Despite the fact that they rarely kill old growth cedars, both are highly contagious and are spread by way of water splash.

The second, more deadly fungus is the Cercospora. These spores attack from the base of the tree and then move upward, turning the tree bronze to light brown within two to three weeks after infection. The inner foliage drops off and eventually the whole tree will appear “naked.”

Look around: most of the cedars in HCR have been infected with some form of blight. This writer recently hired (in 2008) an arborist to take twig and soil samples to determine what type of blight is present (it’s important to know the exact type of fungus as treatment methods differ).

(The tests will take 2 weeks to process and the results will be posted here).

TEST RESULTS UPDATE:

The trees were first attacked by a cedar blight that affected the new growth branches. The new growth tips broke off and browned up. This in turn created stress and opened the junipers up for a massive infestation of spider mites. The exact type of mite was not identified, although it is most probably the spruce spider mite.

Evergreens tend to host other mites, notably the spruce spider mite (Oligonychus ununguis) on spruce and juniper, Oligonychus subnudus on pines, and Platytetranychus libocedri on arborvitae and juniper. Honeylocust, particularly those in drier sites, are almost invariably infested with the honeylocust spider mite (Platytetranychus multidigituli). Other mites may affect shade trees such as elm, mountain ash and oak.)

These mites will also affect the health of other evergreen trees including the bald cypress that we have in our area (down at Cypress Creek). One cypress tree has already succumbed to the mites and is rapidly dying.

This type of massive infestation occurs in cycles depending on the weather patterns. In the case of the spider mites the last major infestation occurred in 1998. The cedars are not going to eradicated by this infestation but unfortunately many suburban homeowners who utilized the naturally drought resistant cedar to provide shaded areas around their homes will find their once stately cedars bald.

Learn More:

•  Colorado State Education