Plant Disease Management Handbook

Cause Sydowia polyspora (formerly Hormonema dematioides), a fungus, has been isolated from needles with current-season needle necrosis (CSNN) from a number of Abies spp., including noble and grand fir from the PNW. The exact role this fungus plays in disease development is unknown. It has become one of the most common needle diseases on these trees in the Pacific Northwest.

Cause The fungus Melampsorella caryophyllacearum causes large brooms on true firs (Abies sp) including A. concolor (white fir), A. magnifica (California red fir) A. amabilis (Cascade fir), A. balsamea (balsam fir), A. grandis (grand fir), and A. lasiocarpa (alpine fir).

See:

Fir, Douglas and True - Laminated Root Rot

Cause Unknown, possibly genetic. Generally not considered a major economic problem. Found throughout the Willamette Valley in Oregon.

Cause A binucleate Rhizoctonia-like fungus, but not the same one that causes root rot or damping-off of seedlings. The disease affects grand, noble, and Douglas-fir. Concerns about the disease in western Hemlock increased substantially in 2019. Some studies have shown balsam fir and Sitka spruce may also be susceptible. The disease is worse in Christmas tree plantations with restricted air flow, close tree spacing, and dense foliage.

Cause The fungus Phoma eupyrena is associated with three different diseases called upper stem canker, lower stem canker, and Phoma blight. The fungus can survive in soil by forming chlamydospores and machinery or blowing soil can transport spores to uninfected areas. Upper stem canker infection occurs when spores land in bark fissures caused by rapid seedling growth. Infection for the other two diseases occurs below the soil collar, which builds up from rain or irrigation-splashed soil.

Cause Dermea boycei (asexual: Faveostroma boycei) and Diaporthe lokoyae (asexual: Phomopsis lokoyea), fungi. Cankers are most often found on trees that are not vigorous or are weak from drought or winter injury, typically 1 to 2 years after the stress. Infections are on new shoots from windblown spores. Mechanical injuries can also be sites for new infections.

See:

Poplar (Populus spp.) - Leaf Rust

Cause The fungus Melampsora occidentalis is the most common cause of needle rust in the Pacific Northwest. The alternate host is black cottonwood and other poplars. The aecial stage is found on the current-year needles. Urediniospores and teliospores are on the alternate host, poplar.

See:

Rhododendron - Ramorum Leaf Blight and Shoot Dieback

Tanoak (Notholithocarpus densiflorus) - Sudden Oak Death

Cause Nothophaeocryptopus gaeumannii, a fungus found on trees of all age classes from natural forests to ornamental landscapes. This disease is considered one of the top threats to Douglas-fir plantation health and productivity in western Oregon, Washington and SW British Columbia.