Plant Disease Management Handbook

Cause Verticillium dahliae, a fungus that lives a long time in soil and can infect a wide range of hosts. Rootstocks such as Rosa odorata and 'Ragged Robin' are susceptible; R. multiflora and 'Dr. Huey' have more resistance. R. chinensis var. manetti is very resistant. Under favorable growing conditions plants may be able to tolerate infection.

See:

Rose Cultivar Resistance

Image related to Rose (Rosa spp.) and hybrids-Rust

Rusty lesions on the underside of the leaves.

Jay W. Pscheidt, 2016.

Numerous spots on these leaves are due to rust.

Jay W. Pscheidt.

Note the two different pustules on this leaf, orange uredia and black telia.

Photo by Jay W. Pscheidt, 1996.

Both rust and black spot can be seen on these leaves.

Haywood Photography, 2005.

Uredinia on the under surface of these leaves.

Jay W. Pscheidt, 2014.

Uredinia are bright orange and raised from the surface of the leaf. Pustule on the right along the leaf vein is just splitting open.

Jay W. Pscheidt, 2014.

See:

Rose (Rosa spp.) and hybrids - Virus Diseases

Image related to Rose (Rosa spp.) and hybrids-Rose Mosaic

Each of these leaves were from the same plant.

Jay W. Pscheidt, 2012.

Symptoms may vary from leaf to leaf infected with rose mosaic.

Jay W. Pscheidt, 2012.

Note the irregular pattern of yellow lines on leaves.

Photo by Jay W. Pscheidt, 1991.

Sometimes the leaf veins are yellow in plants infected with this virus.

Photo by Melodie Putnam, 1997.

See:

Apple (Malus spp.) - Replant Disease

The Washington Park International Rose Test Garden in Portland OR reports that they routinely replant a 1,000 new plants every year and have not noted a replant problem.

Jay W. Pscheidt, 2021.

See:

Rose Cultivar Resistance

Image related to Rose (Rosa spp.) and hybrids-Powdery Mildew

Symptoms are not generally seen on the flower petals but early infections can deform flower buds and affect the bloom.

Jay W. Pscheidt, 2015.

Colonies can seem to cover many of the leaves of susceptible cultivars.

Jay W. Pscheidt, 2015.

Note the dull, white to gray patches on the leaves.

Photo by Jay W. Pscheidt, 1991.

Powdery mildew can occur on either side of the leaf and on petiols.

Jay W. Pscheidt, 2015.

Conidia of powdery mildew. The disease can spread quickly via these spores when conditions are favorable. Here both the conidiophore and the conidia have been stained blue to show up better.

OSU Extension Plant Pathology Slide Set, 1963.

Rose on the left is a resistant cultivar while the rose on the right is quite susceptible to powdery mildew.

Jay W. Pscheidt, 1991.

Cause Nematodes are a big problem in the production areas of California but have not been investigated as a problem in the Pacific Northwest. Soil types, that are more sandy, generally result in more nematode injury at lower population levels. Host ranges are wide for many of these nematodes making crop rotation impractical.

Cause Lime-induced chlorosis, or leaf yellowing, is caused by alkaline soil conditions. High (pH) alkalinity of soils can make iron or manganese unavailable to plants, causing leaf chlorosis. Has been more common in samples from eastern Oregon. Ideal pH for growing roses is from 6.0 to 6.5.

Symptoms The initial symptom is an interveinal chlorosis of the young leaves with the main veins remaining green. These leaves may remain small and become pale yellow to white.

See:

Blackberry (Rubus spp.) - Downy Mildew

Image related to Rose (Rosa spp.) and hybrids-Downy Mildew

Irregular-shaped, purple spots form on the upper leaf surface, while light, gray-brown spore masses form on the underside of the leaf (middle leaflet on right side of this picture).

Photo by Ralph S. Byther

Easily confused for black spot if you are not aware of downy mildew.

Melodie Putnam, 2009.

Sporulation can be seen on the petioles and underside of the leaf.

Kathleen Baughman, 2010.

Unusual symptoms that turned out to be downy mildew on these Double Knockout roses.

OSU Plant Clinic image, 2014.

Note the reddened areas on the sepals and stem.

Photo by Kathy Merrifield, 1990.

See:

Cherry (Prunus spp.) - Crown Gall

Galls occur near soil line as well as near pruning cuts as in this image.

Jay W. Pscheidt, 2013.

Note that the galls have started at pruning wounds. Also, the cross-section of the gall on the right shows disorganized but solid tissue.

OSU Extension Plant Pathology Slide Collection.

Image related to Rose (Rosa spp.) and hybrids-Crown Gall

Galls may be numerous on canes or branches.

OSU Extension Plant Pathology Slide Set, 1984.

Galls can be seen above or below ground.

OSU Extension Plant Pathology Slide Set, circa 1950's.

Most of the time galls appear below ground and may be overlooked as a cause for poor growth.

Melodie Putnam, 2008.

Cause There are a number of herbicides available for use around roses plantings. The herbicide class and the dosage to the plant determine which symptoms appear and their severity. Injury from glyphosate (such as Roundup and related materials) is relatively common. Damage symptoms caused by this herbicide may not appear during the season of application, especially if application is made in autumn, but symptoms may appear the following spring. The plant will outgrow the injury if the dosage was not too high.

Image related to Rose (Rosa spp.) and hybrids-Chemical Injury

Base of this plant has injury from glyphosate.

Neil Bell, 2014.

Injury from glyphosate (left) appears as a proliferation of small shoots and needle-like leaves from buds.

Neil Bell, 2011.

Damage to the rose on the right due to 2,4-D herbicide. On warm days, the herbicide can volatilize and drift in from nearby applications. The ester form of this chemical, commercially available as Crossbow, Brush Killer, and other trade names, is more volatile than the amine form.

Jay W. Pscheidt, 2021.

Damage to the leaves on the right due to 2,4-D herbicide.

Jay W. Pscheidt, 2021.