Rhododendron: Ramorum leaf and shoot blight (Sudden oak death) categories: Ornamentals Rhododendron Rhododendron Diseases Shrubs revision date: 2022-12-05 12:00 P. ramorum shoot blight symptoms on rhododendronPhoto by: M. Elliott Biology Ramorum leaf blight is caused by Phytophthora ramorum, the same organism that causes sudden oak death (SOD). In Washington, most cases have been found in […]
Rhododendron: Rust categories: Ornamentals Rhododendron Rhododendron Diseases Shrubs revision date: 2022-12-05 12:00 Rhododendron rustPhoto by: R.S. Byther Biology Yellowish spots on the upper leaf surface and dark brown or purple spot on the lower leaf surface can indicate the presence of a rust infection. Later, the underside develops blisters which break open to reveal characteristic […]
Rhododendron: Salt injury categories: Ornamentals Rhododendron Rhododendron Diseases Shrubs revision date: 2022-12-05 12:00 Leaf tip necrosis from salt damagePhoto by: R.S. Byther Biology Salt injury to rhododendrons is typically a result of culture or environment. Excessive salt (mineral) levels in the soil or irrigation water, excessive use of chemical fertilizers, or lack of water can […]
Rhododendron: Sunburn categories: Ornamentals Rhododendron Rhododendron Diseases Shrubs revision date: 2022-12-05 12:00 Sunburn on rhododendron leavesPhoto by: R.S. Byther Biology Sunscald is caused by exposure of the leaves to bright sunlight during hot weather. Sunscalded leaves on rhododendrons generally have a yellow to brown blotch in the center. Often this blotch has a yellow halo […]
Rhododendron: Tissue proliferation categories: Ornamentals Rhododendron Rhododendron Diseases Shrubs revision date: 2022-12-04 12:00 Rhododendron tissue proliferationPhoto by: R.S. Byther Biology There is no known cause of tissue proliferation, but it is currently believed to be a genetic abnormality. A swollen area or gall develops at the base of the trunk or (more rarely) on a […]