Cedrus Deodara Trees
Four of my 12 CD trees look stressed. We've had them for 29 years. It was not a particularly harsh winter. I can't think of anything that might have stressed them other then our landscaper performs routine weed control, which he has done every year for about 5 years. There has been no digging in the area. Any ideas or suggestions? Can they be saved? See attached photos.
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If you believe that growing conditions and maintenance (especially soil fertility and water management) is adequate, then consider the possibility of an armored scale insect pest, like "pine needle scale". This is on the increase in the areas that I serviced in California, I'm not sure if the same pests are prevalent in Washington.
The pine needle scale, if that's what it is, is very tiny and individuals are hard to see without a good hand lens or microscope. If it's a heavy infestation, you can sometimes see the masses of white scale insects on needles and twigs.
Definitive diagnosis and treatment needs a professional. First check with your local university/county agricultural, environmental horticulture extension service. If you call a tree service that provides landscape pest control, ask if they have a certified arborist, plant health care specialist on staff to inspect and identify the pest. Suggest that they consider "armored scale" in their assessment; it is not common everywhere and few arborists that I know are aware of it.
There are spray programs available, but timing is critical to target the crawler stage (immature form of the insect), and the risk of environmental contamination is greater, depending on what material is used.
A frequently used treatment of choice, if confirmed as an armored scale infestation, is Safari systemic insecticide, with PentraBark surfactant, as a basal bark treatment. Spraying is on the lower tree trunk only for absorption through the bark, which minimizes environmental exposure. The appropriateness of this treatment should be confirmed and provided by a licensed pesticide applicator. It's not available for homeowner use. The material is low toxicity for mammals, but highly toxic to fish and honey bees.
This article will give you some more information on growing deodar cedar trees: (Did you know that they are native to the Himilayan foothills and the national tree of Pakistan).
Please let us know if you have any other gardening questions and happy gardening!
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