WSU Extension

Hortsense

Arborvitae
 
Disease
Berckmann's blight 
Cedar flagging 
Leaf blight 
Shoot tip dieback 
Twig blight 
Insect
Cypress tip moth 
Flat-headed and shothole borers 
Juniper scale 
Juniper webworm 
Leafminers 
Spider mites 
Spruce bud scale 



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Caption: Cedar flagging
Photo by: R.S. Byther
  
Arborvitae : Cedar flagging
(revision date: 4/23/2014)


Biology
Evergreen plants naturally shed some old foliage each year. Stress factors, such as lack of sufficient water, hot winds, construction damage or other root disturbance, poor planting procedures, or recent planting can promote flagging. Brown foliage develops on the tree or shrub in mid- to late summer and is very obvious by early fall. The affected foliage consists of older growth formed in previous years. Foliage developed during the current year (at the branch tips) remains green. These brown branchlets are called flags and are generally spread uniformly throughout the canopy. Affected foliage may begin to drop during hot, dry weather. Most of the dead foliage is blown out of the plant by the wind in fall and winter, and the plant typically resumes its healthy appearance.
Management Options


Non-Chemical Management
  • Additional irrigation may be needed during periods of summer drought.
  • Alleviate root disturbance from construction damage or other factors.
  • Correct poor planting practices when feasible. If affected plants were planted too deeply, it may be possible to replant them during the dormant season if they are not too large.
  • Improve drainage if the planting site has constantly wet soil. Construct a French drain or grade the soil to divert water away from the planting site. Replant the affected specimen onto a berm or raised bed, or transplant to a site with better drainage.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images

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Caption: Cedar flagging
Photo by: R.S. Byther
Caption: Cedar flagging close-up
Photo by: R.S. Byther