WSU Extension

Hortsense

Rhododendron
 
Disease
Armillaria root rot 
Botrytis shoot blight 
Gray blight 
Leaf spot 
Lime-induced chlorosis 
Marginal leaf necrosis 
Physiological leaf spot 
Phytophthora blight 
Phytophthora root rot 
Powdery mildew 
Ramorum leaf and shoot blight (Sudden oak death) 
Rust 
Salt injury 
Sunburn 
Tissue proliferation 
Insect
Aphids 
Azalea bark scale 
Caterpillars 
Lecanium scale 
Rhododendron lace bug 
Rhododendron whitefly 
Root weevils 



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Caption: Lime-induced chlorosis
Photo by: R.S. Byther
  
Rhododendron : Lime-induced chlorosis
(revision date: 4/23/2014)


Biology
Lime-induced chlorosis, or leaf yellowing, is caused by alkaline soil conditions. High alkalinity of soils can make iron or manganese unavailable to plants, causing leaf chlorosis. Pale to bright yellow leaves, particularly on the new growth, are common symptoms. Typically the chlorosis begins at the edges and progresses into the leaf, with only the veins remaining green in severe cases.
Management Options


Non-Chemical Management
  • Adjust soil pH to 4.5-6.0. Addition of sulfur or organic matter, especially conifer needle mulch, which is highly acidic, may be beneficial. Work soil under plant carefully to avoid damage to the shallow root system.
  • Use iron chelate, either as a soil treatment or by foliar feeding, to quickly help chlorotic plants. Read and follow all label instructions.
  • Check plant's proximity to newly poured concrete. New concrete leaches lime into the surrounding soil, raising the pH.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images

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Caption: Lime-induced chlorosis
Photo by: R.S. Byther
Caption: Iron deficiency
Photo by: R.S. Byther