Rhododendron: Powdery mildew categories: Ornamentals Rhododendron Rhododendron Diseases Shrubs revision date: 2024-06-05 10:40 Powdery mildew causing yellow spots on rhododendronPhoto by: C.R. Foss Biology Powdery mildew on rhododendrons is a fungal infection of the leaves. On rhododendrons, the disease often fails to develop the distinctive powdery white growth normally associated with powdery mildews. Leaves may […]
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: Aphids categories: Ornamentals Rhododendron Rhododendron Insects Shrubs revision date: 2024-06-05 08:28 Aphid damage on rhododendronPhoto by: A.L. Antonelli Biology Aphids cause twisting, curling, or puckering of new growth by their feeding. Whitish cast skins and green live aphids may be visible on the undersides of leaves. Honeydew, a shiny, sticky substance excreted by aphids, […]
Rhododendron: Azalea bark scale categories: Ornamentals Rhododendron Rhododendron Insects Shrubs revision date: 2024-06-05 08:28 Azalea bark scale and sooty moldPhoto by: A.L. Antonelli Biology The azalea bark scale is a soft scale resembling mealybugs. Red females cover themselves and their eggs with a white, waxy protective coating. Cottony masses of the scales are often located […]
Rhododendron: Caterpillars categories: Ornamentals Rhododendron Rhododendron Insects Shrubs revision date: 2024-06-05 02:10 Looper crawling on edge of rhododendron leafPhoto by: S.J. Collman Biology Several caterpillar pests occur on rhododendrons, most notably cutworms, loopers, and the obliquebanded leafroller. Cutworms and loopers (various species) feed on leaf tissue, removing large, irregularly-shaped pieces. They are night-feeders and may […]
Rhododendron: Lecanium scale categories: Ornamentals Rhododendron Rhododendron Insects Shrubs revision date: 2024-06-05 02:08 Lecanium scales on twigPhoto by: R.S. Byther Biology Lecanium scale adults are found on the twigs in late spring. At this stage they are usually brown or mottled brown and white bumps on the stems. During the summer and fall, scale nymphs […]
Rhododendron: Rhododendron lace bug categories: Ornamentals Rhododendron Rhododendron Insects Shrubs revision date: 2024-06-05 02:07 Rhododendron lacebug symptoms on leavesPhoto by: C.R. Foss Biology The rhododendron lace bug causes stippling on the upper surface of the leaves, and deposits crusty or tar-like excrement on the lower surface. Adult insects are whitish-tan and approximately 1/8″ long with […]
Rhododendron: Rhododendron whitefly categories: Ornamentals Rhododendron Rhododendron Insects Shrubs revision date: 2024-06-05 08:28 Rhododendron whitefly damagePhoto by: A.L. Antonelli Biology Whiteflies are small white insects that hold their wings rooflike over their abdomens rather than flat like true flies. Infested leaves, usually the tender young leaves at the branch tips, are mottled yellow on the […]
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 […]
Rhododendron: Root weevils categories: Ornamentals Rhododendron Rhododendron Insects Shrubs revision date: 2023-04-04 12:00 Root weevil damage on rhododendron leavesPhoto by: A.L. Antonelli Biology Several species of weevils feed on rhododendrons. Characteristic damage includes notching of leaf edges by adults and minor to severe root and bark damage by larvae. Occasionally the larvae girdle the trunk […]
Viburnum: Bacterial blight (Leaf spot) categories: Ornamentals Shrubs Viburnum Viburnum Diseases revision date: 2024-06-05 10:24 Viburnum bacterial blight (leaf spot)Photo by: R.S. Byther Biology Bacterial blight of viburnum primarily affects leaves and occasionally stems. Spots on leaves first appear as brown, watersoaked areas which may be round, irregular, or angular in outline. Developing leaves may […]
Viburnum: Leaf spot categories: Ornamentals Shrubs Viburnum Viburnum Diseases revision date: 2024-06-05 02:07 Viburnum leaf spotPhoto by: J.R. Glass Biology Various fungi cause leaf spot symptoms on viburnum. The spots are typically necrotic brown spots of varying sizes. At least one bacterial leaf spot is also common. Management Options Use Integrated Pest Management (IPM) for […]
Viburnum: Powdery mildew categories: Ornamentals Shrubs Viburnum Viburnum Diseases revision date: 2024-06-05 02:07 Powdery mildew on viburnum leafPhoto by: B.M. Johnson Biology Powdery mildew of viburnum is a fungal disease which primarily affects young leaves and shoots. Affected plant tissues develop a powdery white growth of fungal mycelia. The fungus can be found on either […]
Viburnum: Ramorum leaf and shoot blight (Sudden oak death) categories: Ornamentals Shrubs Viburnum Viburnum Diseases revision date: 2022-12-04 12:00 P. ramorum leaf tip necrosis symptom on viburnumPhoto 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 […]
Viburnum: Shoot blight (Gray mold) categories: Ornamentals Shrubs Viburnum Viburnum Diseases revision date: 2022-12-04 12:00 Viburnum Botrytis stem rotPhoto by: R.S. Byther Biology Shoot blight of viburnum is caused by Botrytis cinerea, a fungus commonly found on ornamentals, greenhouse plants and flowers, vegetables, and small fruits. Viburnums develop gray to brown spots along the leaf […]
Viburnum: Bean aphids categories: Ornamentals Shrubs Viburnum Viburnum Insects revision date: 2024-06-05 02:04 Bean aphid on leafK. Grey Biology Bean aphids are soft-bodied dark green to black insects commonly found on the undersides of leaves and on new growth. They often occur in dense colonies. Heavy aphid feeding may distort shoot tips and leaves, and […]
Viburnum: Root weevils categories: Ornamentals Shrubs Viburnum Viburnum Insects revision date: 2023-04-04 12:00 Root weevil damage on viburnumPhoto by: A.L. Antonelli Biology Root weevil larvae feed on the roots and bark of plants near the crown. The white grubs are found in the soil around the roots. Heavy feeding by root weevil larvae can cause […]