Plant Disease Management Handbook

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Spruce (Picea spp.) - Phytophthora Root Rot

Both Cylindrocarpon and Rhizoctonia were recover from these roots.

OSU Plant Clinic, 2022.

Cause Fusarium sp. is suspect. Fusarium oxysporum was found repeatedly during 2012 and 2013 in association with dying plants in Oregon seed fields. The fungus is soilborne and can survive in soil, often in plant debris, for at least several year as durable resting spores known as chlamydospores. The fungus can be spread by infested equipment or windborne or waterborne movement of infested soil.

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Apple (Malus spp.) - Scab

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Peach (Prunus persica) - Powdery Mildew

The development of rusty spot symptoms from young lesions to russetted fruit, left to right.

Norm Lalancette, 2016.

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Cedar, Port-Orford (Chamaecyparis lawsoniana) - Root Rot

Microbiota decussata (Russian cedar) with die-back due to Phytophthora root rot.

Oregon State University Plant Clinic image, 2016.

Progression of foliage symptoms displayed by Microbiota decusatta (Russian cypress) when infected by Phytophthora lateralis, showing initial bronzing of foliage (center) followed by plant death (left).

Jennifer Parke

Heavily (left) and moderately (center) infected root systems show the extent of root necrosis attributable to Phytophthora lateralis. The plant on the right is healthy.

Jennifer Parke

Infection of young Microbiota decusatta by Phytophthora lateralis causes both stunting and reduced root mass.

Jennifer Parke

Cause The fungus Cryptostroma corticale has been causing dieback primarily in sycamore maples (Acer pseudoplatanus), although several other species can also become infected. The disease was found in eastern WA in 1968 and in the Seattle area in 2020 on sycamore maple, red maple (Acer rubrum), Japanese maple (A. palmatum), vine maple (A.

Bark sloughs away exposing dark patches of the fungal stroma and powdery spores.

Joey Hulbert, 2023.

Bark sloughs away exposing dark patches of the fungal stroma and powdery spores.

Joey Hulbert, 2023.

Canopy dieback, epicormic shoots along the trunk and if you look closely you see dark patches on the trunk.

Joey Hulbert, 2022.

Low resolution image showing that trees may have a greenish-brown-to-greenish-yellow stain of the wood that can be seen when an infected branch is cut into cross-section.

Gary Chastagner.

Bark section from maple tree with dark patches of black fungal stroma and powdery black spores.

OSU Plant Clinic, 2022.

Cause The fungus Erysiphe magnifica (formerly Microsphaera magnifica) has been reported from Washington and powdery mildew has been observed on magnolia in Oregon. The Magnolia collection of the Washington Park Arboretum, University of Washington, Seattle, includes 34 species and M. liliiflora was the only species on which powdery mildew was observed in 2003.

Powdery mildew has almost completely covered this young leaf.

Jay W. Pscheidt, 2020.

Cause The fungus Neoerysiphe galeopsidis has been reported from Washington and powdery mildew has been observed in Oregon on Lamb's ear plants. Although plants do not die, the conspicuous disease signs detracted significantly from the appearance of the infected plants.