Plant Disease Management Handbook

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Greenhouse Plants, Ornamental - Impatiens Necrotic Spot

Cause There are 14 viruses reported for hydrangea. Hydrangea ringspot virus (HRSV) can be transmitted mechanically by leaf contact or by knives but not through seed or by aphids. Suspected as cause of hydrangea running-out. Many cultivars are tolerant of the virus.

Image related to Hydrangea-Ringspots
Image related to Hydrangea-Ringspots

Not a great picture but you can see the reddish spots on the leaves from Hydrangea ringspot virus.

OSU Extension Plant Pathology Slide Set, 1984.

Image related to Hydrangea-Ringspots

Leaf spots from these viruses look similar. Tomato spotted wilt on the left and Hydrangea ringspot on the right.

OSU Extension Plant Pathology Slide Set.

Cause Erysiphe friesii var. friesii (formerly Microsphaera friesii) has been reported from Washington and Erysiphe polygoni has been reported from British Columbia. These fungi are favored by conditions that produce high humidity but dry leaves such as heavily-shaded growing sites. It is a highly specialized pathogen that forms a close association with the host.

Image related to Hydrangea-Powdery Mildew
Image related to Hydrangea-Powdery Mildew

Note the whitish patches on these leaves.

Jay W. Pscheidt, 2014.

Powdery mildew was in association with these distorted leaves.

Oregon State University Plant Clinic image, 2018.

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Greenhouse Plants, Ornamental - Gray Mold

Note the brown sporulation on the central, necrotic floret.

Photo by Jay W. Pscheidt, 1998.

Image related to Hydrangea-Bud and Flower Blight

Young cuttings can also be infected in moist conditions.

OSU Plant Clinic collection, 2012.

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Calla Lily (Zantedeschia spp.) - Soft Rot

Cause Pectobacterium carotovorum, a bacterium that survives on plant debris. The disease is widely distributed but infrequent.

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Fir, True (Abies spp.) - Rusts

In the center are dark old telia while new telia are forming to either side. They start out white and progressively turn dark red from the bottom up.

Jay W, Pscheidt, 2008.

Leaves are OK but stems are overly thickened.

Photo by Jay W. Pscheidt, 1993.

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Tanoak (Notholithocarpus densiflorus) - Sudden Oak Death

Rhododendron - Ramorum Leaf Blight and Shoot Dieback

Image related to Huckleberry (Vaccinium spp.)-Ramorum Leaf Blight and Shoot Dieback
Image related to Huckleberry (Vaccinium spp.)-Ramorum Leaf Blight and Shoot Dieback
This sprout is brown and necrotic with tip dieback from this disease.
Photo by Everett Hansen
Image related to Huckleberry (Vaccinium spp.)-Ramorum Leaf Blight and Shoot Dieback
Note stems and leaves with dieback symptoms.
Photo by Djibo Zanzot

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Blueberry (Vaccinium corymbosum) - Mummy Berry

Image related to Huckleberry (Vaccinium spp.)-Mummy Berry
Image related to Huckleberry (Vaccinium spp.)-Mummy Berry

Note the spots on the leaves.

OSU Extension Plant Pathology Slide Set.

Image related to Huckleberry (Vaccinium spp.)-Mummy Berry

Red arrow points to mummified fruit of black huckleberry, Vaccinium membranaceum. Mount Revelstoke and Glacier National Parks, British Columbia.

Mindy Skinner, 2014.

Mummy berry found on Vaccinium membranaceum in the Wallowa mountain area.

Christina Hagerty, 2018.

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Azalea (Rhododendron spp.) - Leaf and Flower Gall

Puckered areas on leaves due to Exobasidium sp.

OSU Extension Plant Pathology Slide Collection, 1960.

Note the puckered areas on the leaves.

OSU Extension Plant Pathology Slide Collection, 1960.

Exobasidium vaccinii on evergreen huckleberry, note the reddish-orange coloration of infected leaves.

Jay W. Pscheidt, 1991.

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Greenhouse Plants, Ornamental - Gray Mold

Notes: Very few samples of this plant have been sent to the OSU Plant Clinic and none were diagnosed with Botrytis.

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Greenhouse Plants, Ornamental - Impatiens Necrotic Spot

Image related to Hosta-Viruses
Image related to Hosta-Viruses
Hosta Virus X with symptoms of leaf puckering and mosaic.
Photo by Melodie Putnam, 2005
Image related to Hosta-Viruses
Hosta Virus X mosaic symptoms.
Melodie Putnam, 2006.