Common Diseases: Armillaria root rot categories: Common Diseases Common Problems last review date: 2026-03-27 11:02 White fungal mat of Armillaria root rot infecting trunk Photo by: C.R. Foss Biology Armillaria root rot is a fungal disease transmitted between plants by root contact. It is also spread by rhizomorphs. Armillaria is often found in newly cleared […]
Common Diseases: Botrytis blight (Gray mold) categories: Common Diseases Common Problems last review date: 2026-03-27 11:25 Botrytis sporulating on alder seedling Photo by: R.S. Byther Biology Water-soaked lesions appear and quickly become covered with a gray-brown mass of fungus and spores. Infection often occurs at injury sites. After initial infection, gray mold can spread into […]
Common Diseases: Cankers categories: Common Diseases Common Problems last review date: 2026-03-27 11:47 Black canker and peeling bark on madrone Photo by: R.S. Byther Biology Cankers are localized wounds or necrotic lesions, often sunken beneath the surface of the stem of a woody plant. Cankers can be caused by fungi, bacteria, or winter damage. Determining […]
Common Diseases: Crown gall categories: Common Diseases Common Problems last review date: 2026-03-28 09:30 Crown gall on roots Photo by: R.S. Byther Biology Crown gall is found on many ornamental plants, fruit trees, and caneberries. It is most commonly found on cherry, apple, peach, pear, plum, euonymus, rose, raspberry, and blackberry. Crown gall is caused […]
Common Diseases: Damping-off categories: Common Diseases Common Problems last review date: 2026-03-28 09:36 Damping-off of cucumber seedlings Photo by: R.S. Byther Biology Damping-off is caused by fungi that remain in the soil for long periods of time. Infected seeds decay without germinating. Seedlings may be infected and fail to emerge from the soil. Emerging seedlings […]
Common Diseases: Dead roots categories: Common Diseases Common Problems last review date: 2026-03-28 09:40 Dead roots and healthy roots in nursery plants Photo by: R.S. Byther Biology A plant showing symptoms of off-color, stunting, wilting, and death may be suffering from a root problem. Dead and discolored roots result from factors such as fungal root […]
Common Diseases: Dodder categories: Common Diseases Common Problems last review date: 2026-03-28 09:44 Dodder entwining fuchsia stem Photo by: R.S. Byther Biology The parasitic flowering plant dodder (Cuscuta spp.) attacks living plants by entwining them in its slender stems. Dodder is characterized by its tangle of leafless, yellow to orange threadlike stems. The stems encircle […]
Common Diseases: Downy mildew categories: Common Diseases Common Problems last review date: 2026-03-28 09:49 Lettuce leaf infected with downy mildew fungus Photo by: R.S. Byther Biology Downy mildew is a fungal disease of tender green tissues including leaves and shoots. Infected leaves show areas of slightly chlorotic to purplish red to dark brown discoloration on […]
Common Diseases: Dwarf mistletoe categories: Common Diseases Common Problems last review date: 2026-03-28 09:55 Dwarf mistletoe in conifer Photo by: R.S. Byther Biology Dwarf mistletoe is a parasitic plant that grows on the branches or occasionally on the trunk of a host tree, such as Douglas-fir, true firs, larch, pine, and junipers. It is yellow-green, […]
Common Diseases: Galls categories: Common Diseases Common Problems last review date: 2026-03-28 10:04 Camellia leaf gall Photo by: R.S. Byther Biology A gall is a swelling or overgrowth produced on a plant as a result of infection by certain pathogens or physiological stress. Galls may be found on leaves, stems, trunks or roots. They can […]