Plant Disease Management Handbook

Cause The fungus Erysiphe magnifica (formerly Microsphaera magnifica) has been reported from Washington and powdery mildew has been observed in Oregon on Magnolia. 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.

White-to-grayish patches of powwdery mildew on both leaf surfaces and stems.

Jay W. Pscheidt, 2020.

Cause Several fungal leaf spots have been found in the Pacific Northwest on hydrangea. The OSU Plant Clinic has found Phoma sp. most often, followed by one sample each of Alternaria sp., Ascochyta sp. and Stemphylium sp. Leaf spots due to Ascochyta sp. and Phyllosticta sp. have been found in British Columbia.

Leaf spot caused by Phoma exigua on Hydrangea 'Endless Summer'.

Oregon State University Plant Clinic image, 2010.

See:

Blueberry (Vaccinium corymbosum)-Rust

Huckleberry (Vaccinium spp.) - Witches' Broom Rust

Rust on Vaccinium membranaceum caused by Naohidemyces vacinii.

Jay W. Pscheidt, 2020.

By C. M. Ocamb

By K. Frost and C. M. Ocamb

Hemp shoot showing early symptoms due to infection by Hop latent viroid.

Photo by K. Frost, Oregon State University.

Hemp shoot showing later stage symptoms due to infection by Hop latent viroid.

Photo by K. Frost, Oregon State University.

Detached hemp leaves that are positive for Hop latent viroid.

Photo by C.M. Ocamb, Oregon State University, 2021.

By C. M. Ocamb

A detached hemp branch showing a stem lesion due to a Sclerotinia infection.

Photo by Hannah Rivedal, 2019.

Flower buds on a hemp plant that are infected by Sclerotinia sclerotiorum. Note the white-colored mycelium that is characteristic of this fungus.

Photo by Cynthia M. Ocamb, 2020.

Flower bud on a hemp plant that is infected by Sclerotinia sclerotiorum. The white-colored mycelium that is characteristic of this fungus is evident along with developing (white-colored) and maturing (black-colored) small, dense fungal masses known as sclerotia, which function as survival structures.

Photo by Cynthia M. Ocamb, 2020.

By K. Frost and C. M. Ocamb

A hemp plant exhibiting symptoms of infection of Beet curly top virus in August. Note that some shoot portions appear unaffected while others show twisting and curling of leaflets characteristic of this disease.

Photo by C. M. Ocamb, Oregon State University, 2021.

Closer view of a hemp shoot exhibiting leaf curling and twisting due to Beet curly top virus.

Photo by C. M. Ocamb, Oregon State University, 2021.

Detached hemp leaves that exhibit twisting and deformities due to Beet curly top virus.

Photo by C.M. Ocamb, Oregon State University, 2021.

Detached hemp buds that exhibit twisting and deformities of leaf tissues due to Beet curly top virus.

Photo by C.M. Ocamb, Oregon State University, 2021.

See:

Hemp (Cannabis sativa) -Root and Crown Rot

By C. M. Ocamb

Cause The fungus, Fusarium proliferatum, which can survive in plant debris in soil and has a broad host range. This can affect plants in the field, greenhouse, and vegetative propagation set-ups.

See:

Blueberry (Vaccinium corymbosum) - Rust

Willow (Salix spp.) - Rust