Plant Disease Management Handbook

By K. Frost and C. M. Ocamb

Cause Colletotrichum coccodes, a fungus with a wide host range and present in many potato-growing regions.

Image related to Potato (Solanum tuberosum)-Black Dot

Foliar symptoms of black dot are similar to Verticillium or Rhizoctonia diseases.

Photo by Phil Hamm.

Notice here the black dot stem infections.

Photo by Phil Hamm

Notice the characteristic tiny, black sclerotia within the infected stems.

Photo by Phil Hamm

A tuber infected with black dot.

Photo by Phil Hamm

Close-up of an infected tuber with black dot.

Photo from OSU Extension Plant Pathology Slide Col

By K. Frost and C. M. Ocamb

Image related to Potato (Solanum tuberosum)-Bacterial Soft Rot, Blackleg and Lenticel Rot

Soft rot of potato tuber.

Photo from OSU Extension Plant Pathology Slide Col

Potato plant showing early wilting symptoms of blackleg.

Photo by Ken Frost, 2016.

Potato plant showing stem collapse due to blackleg.

Photo by Ken Frost, 2016.

Potato showing blackleg symptoms.

Photo by Ken Frost, 2017.

Note the black lesion at the stem base and aerial tubers on stems.

Photo by Phil Hamm.

Black leg symptoms are seen here on the potato stems.

Photo from OSU Extension Plant Pathology Slide Col

By P. B. Hamm and C. M. Ocamb

See:

Potato (Solanum tuberosum) - Purple Top

Image related to Potato (Solanum tuberosum)-Aster Yellows (Late-breaking Virus)

Note the yellow, curled leaves.

Photo by Paul Koepsell, 1983.

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Cedar, Port Orford (Chamaecyparis lawsoniana)

Cause The fungus Erysiphe adunca var. adunca (formerly Uncinula salicis) has been reported from British Columbia and the disease has been reported throughout the Pacific Northwest. Phyllactinia populi has also been reported from North America. Occasionally encountered on suppressed understory leaves of cottonwood and hybrid poplar.

Cause Drepanopeziza populi-albae (formerly Marssonina populi or M. castagnei) and M. piriformis, fungi, have been reported form Oregon. In British Columbia M. brunnea f. sp. trepidae, M. castagnei, and M. populi have been found.

Note the numerous leaf spots.

OSU Extension Plant Pathology Slide Collection, 1973.

Leaf spots are all due to Marssonina sp.

OSU Plant Clinic image, 2011.

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Maple (Acer spp.) - Leaf Scorch

Leaves have marginal burn and some so bad that only the leaf veins have remained green. Lack of water uptake due to black root rot in this case.

OSU Plant Clinic image, 2009.

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Fir, Douglas (Pseudotsuga menziesii) - Rust

Image related to Poplar (Populus spp.)-Leaf Rust

Angular, yellow spots appear on infected leaves.

Photo by Ralph S. Byther

Small bright-yellow uredinia can be seen on the underside of these leaves of cottonwood.

Phil Hamm, 1993.

See:

Peach (Prunus persica) - Leaf Curl

Note the puckered, yellow areas on the leaves.

OSU Extenison Plant Pathology Slide Collection, 1980.

Image related to Poplar (Populus spp.)-Leaf Blister

Irregular, convex blisters form on the upper surface of leaves, while a yellow bloom develops on the underside of the blister.

Photo by Ralph S. Byther

Upper surface of the leaf puckers out from this disease.

Jay W. Pscheidt, 2008.

Cause The fungus Venturia populina is found on Lombardy poplar (P. nigra 'Italica') and eastern cottonwood (P. deltoides). The fungus Venturia inopina is found on black cottonwood (Populus trichocarpa) and on other Populus spp. in selections Tacamaha and Aigeiros and their hybrids.

Image related to Poplar (Populus spp.)-Leaf and Shoot Blight

Note the single shoot that has turned black and died back.

Photo by Jay W. Pscheidt, 1994.

Many leaves on these aspens are necrotic from Venturia infection.

Jay W. Pscheidt.