WSU Extension

Hortsense

Common Cultural Problems
 
Air pollution 
Chlorosis 
Construction damage 
Desiccating wind 
Drought damage 
Fasciation 
Fertilizer burn 
Frost injury 
Hail damage 
Lime-induced chlorosis 
Marginal leaf necrosis 
Morphological changes 
Mosses and lichens 
Needle loss 
Needle tip necrosis 
Nutrient deficiency 
Oedema 
Overwatering or poor drainage 
Plant girdling and circling roots 
Poor pollination 
Salt damage 
Sunscald 
Transplant shock 
Winter desiccation 
Winter injury 



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Caption: Lichens on rhododendron branches
Photo by: C.R. Foss
  
Common Cultural : Mosses and lichens
(revision date: 4/30/2013)


Biology
Mosses and lichens are primitive plants often found growing on the bark of older trees and shrubs. They are typically grayish, greenish, or orange in color and may be flat or branched. Mosses and lichens are not parasitic and will not harm the trees. They are often associated with shaded or declining trees, but do not cause decline. Regular pruning usually limits development of mosses and lichens.
Management Options

Non-Chemical Management
  • Plant in sunny locations. Prune to allow more light into the canopy.
  • Provide proper plant culture. Vigorous trees are not at any risk from moss and lichen development.
  • Remove heavy buildups of mosses and lichens by hand, when practical.
Select non-chemical management options as your first choice!

Chemical Management

Fungicides are not usually recommended.

Images

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Caption: Lichens on rhododendron branches
Photo by: C.R. Foss
Caption: Lichens on rhododendron branches
Photo by: C.R. Foss
Caption: Lichens on walnut
Photo by: J.W. Pscheidt