Plant Disease Management Handbook

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Blackberry Cultivar Susceptibility

Nice close-up of a typical lesion.

Photo by Ken Brown, 1980.

Image related to Blackberry (Rubus spp.)-Purple Blotch

During winter and spring, lesions become purple with a red margin.

OSU Plant Clinic Image, 2013.

Affected areas develop into cankers and girdle canes of this Marion blackberry.

OSU Plant Clinic Image, 2013.

Cause Podosphaera macularis (formerly Sphaerotheca macularis) , a fungus. Powdery mildew causes fruit loss in some Pacific Northwest plantings each year. 'Boysenberry' is very susceptible while 'Loganberry' is less susceptible; however, most other blackberries and their hybrids are generally not affected by this disease.

Notice the white powdery colonies.

Jay W. Pscheidt,2020.

The underside of a Boysenberry leaf with nice white powdery colonies.

OSU Extension Plant Pathology Slide Collection, 1977.

Cause Gymnoconia nitens (formerly Arthuriomyces peckianus), a fungus that was rarely found in the Pacific Northwest but common in eastern North America. Records at OSU's Mycological Herbarium and Plant Clinic indicate that "orange rust" was found from 1913 to 1923 in Douglas, Hood River, Umatilla, Union, and Wasco counties of Oregon. In 1997, G. nitens was found on 'Kotata' blackberries in an isolated field in the Willamette Valley.

Infected primocane of Black Diamond with orange aecia on the left and healthy primocane on the right.

Jay W. Pscheidt, 2021.

Many weak, spindly shoots (left side) arise from infected roots and crowns of these Black Diamond plants in spring (healthy shoots right side).

Jay W. Pscheidt, 2021.

Close up of the underside of two blackberry leaves

Note the bright orange aecia on 'Kotata' blackberry.

Photo by Jay W. Pscheidt, 1997.

Blackberry bushes in bloom with orange leaf among green ones.

Lower leaf surfaces become covered with blister-like pustules (aecia).

Jay W. Pscheidt, 2021.

Upper leaf surface of Himalaya blackberry develops chlorotic spots and areas opposite where aecea develop below.

Jay W. Pscheidt, 2021.

Blackberry shoots with some yellow, orange and green leaves.

Orange rust can develop on wild blackberry. Note many of these Himalaya blackberry plants in this image are not showing symptoms.

Jay W. Pscheidt, 2021.

Cause A survey in 2015 found the majority of isolates to be Botrytis cinerea, a fungus. This fungus is ubiquitous and attacks many different fruit and ornamental crops. A moist, humid environment is ideal for sporulation and spread of this fungus. Wet weather just before and during bloom is important for disease development. All flower parts are very susceptible. Initial infections of flowers may be latent, such that the fungus is dormant until fruit ripens.

Botrytis on blackberries in the field.

Lisa Jones, 2018.

Image related to Blackberry (Rubus spp.)-Fruit Rot

Rotted fruit with tufts of gray fungus growing on the surface.

Dept of Horticulture, OSU

Note the fuzzy growth on the fruit.

OSU Extension Plant Pathology Slide Collection, 1962.

Note the gray fuzzy growth of the fungus between individual druplets.

Photo by Walter F. Mahaffee, 1998

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Raspberry (Rubus spp.) - Dry Berry

Image related to Blackberry (Rubus spp.)-Dry Cell (Dry Berry) Syndrome

Note that individual druplets of this Marionberry have turned gray and necrotic.

Photo by Walter F. Mahaffee, 1997

These berries have sunburn where large sun exposed sections have discolored and begun to dry.

Jay W. Pscheidt, 2010.

Affected druplets may be widely scattered or clustered in patches.

Photo by Walter F. Mahaffee, 1998

Image related to Blackberry (Rubus spp.)-Sunburn

Sun and heat damage to Natchez Thornless blackberry shows various types of symptoms from white drupelets, to red drupelets, to dryness and “jamming”.

Bernadine Strik, 2016.

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Rose (Rosa spp.) and hybrids - Downy Mildew

Image related to Blackberry (Rubus spp.)-Downy Mildew

Note the deep-red coloration along the main veins of the leaves.

Photo by Jay W. Pscheidt, 1990.

The receptacle of infected berries may split down the middle. These berries dry out and may look like doubles.

Photo by Jay W. Pscheidt, 1990.

Red angular leaf spots on top (left) while sporulation usually occurs on the underside of the leaf (right).

OSU Plant Clinic image, 2013.

Some cultivars show numerous atypical lesions on leaves, but like typical symptoms, lesions are angular along leaf veins.

OSU Extension Plant Pathology Slide Collection, 1991.

See:

Blackberry Cultivar Susceptibility

Image related to Blackberry (Rubus spp.)-Crown and Cane Gall

Galls may look creamy white when they first emerge.

Eric Gabriel, 2008.

It is more typical to find galls just below the ground level as on this Marionberry.

Melodie Putnam, 2010.

Galls can occur on roots as on this Boysenberry plant.

OSU Plant Pathology Slide Collection, 1972.

Not all canes will show the problem and some will remain green despite the extensive vascular disruption.

Eric Gabriel, 2008.

Hans P. P. Wittig shown here holding a wild blackberry with cane gall.

Photo by Jay W. Pscheidt, 1993.

Crown gall appears on fruiting canes as small rough ridges or elongated overgrowths of granular gall tissue.

OSU Extension Plant Pathology Slide collection.

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Raspberry (Rubus spp.) - Cane Blight

Note: 'Boysenberry', 'Loganberry', and 'Youngberry' canes are seldom infected with cane blight unless canes first are frozen, pruned, or mechanically damaged.

Cane blight was resulting in poor growth and dieback of this blackberry.

OSU Plant Clinic image, 2013.

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Blackberry Cultivar Susceptibility

Note the yellow, oval pustules on the center cane.

OSU Extension Plant Pathology Slide, 1972.

Image related to Blackberry (Rubus spp.)-Cane and Leaf Rust

Spores infect leaves and produce small yellow pustules (uredinia) on the undersides.

Dept of Horticulture, OSU

This rust fungus can also attack the drupelets of this 'Columbia Star' blackberry.

OSU Plant Clinic Image, 2014.

See:

Blackberry Cultivar Susceptibility

Image related to Blackberry (Rubus spp.)-Blackberry Rust

Blackberry rust on Evergreen flowers.

Haywood Photography, 2005.

Blackberry rust on Evergreen on both the top and bottom of the leaves.

Haywood Photography, 2005.

An Evergreen blackberry field on the left and a Marion blackberry field on the right. The left half of of the Evergreen field is severely infected with rust.

Haywood Photography, 2005.

A severely infected field of Evergreen blackberries. Plants at the end of the row are not as badly infected.

Photo by Jay Pscheidt, 2005.

Blackberry rust on Evergreen stems is rare even in severely infected fields.

Photo by Jay Pscheidt, 2005.

Blackberry rust on the lower surface of leaves of wild, fence row blackberries. Is is also shown on the flowers. Note the black telia as well as the orangeish uridinia.

Haywood Photography, 2005.

Blackberry rust on upper surface of leaves of wild, fence row blackberries.

Haywood Photography, 2005.

Blackberry rust on wild Himalayan blackberries found along a fence near cultivated blackberries.

Photo by Jay Pscheidt, 2005.