Georgia rose growers know all too well the devastation that black spot can wreak on roses. Planting roses resistant to black spot is the best way to avoid problems. The following article lists some of the most disease-resistant roses for the South.
MANAGE ROSE BLACK SPOT WITH DISEASE-TOLERANT CULTIVARS
By John Hartman, University of Kentucky Plant Pathologist
Roses are a popular landscape and garden plant in Kentucky. Black spot, caused by the fungus Diplocarpon rosae, is the most important foliar disease of roses in Kentucky. It is a serious problem every year under our warm, humid growing conditions. Infected leaves become spotted, turn yellow and drop from the plant. This defoliation decreases plant energy reserves and results in reduced flowering of roses. Kentucky growers wanting to maintain good health of their susceptible rose cultivars are almost obligated to use repeated applications of fungicides throughout the growing season. If rose growers could grow genetically resistant or disease tolerant roses, they would benefit from improved performance and reduced fungicide use.
Rose cultivars are evaluated for disease reactions. Plant Pathologists from around the U.S. periodically evaluate rose cultivars for their reaction to black spot disease. The following black spot-resistant rose lists were assembled from reports of evaluations done in Virginia, Louisiana, Florida, Texas, and Washington. Some of these test results were printed in recent issues of Biological and Cultural Tests for Control of Plant Diseases, an annual journal published by the American Phytopathological Society. Many of these cultivars are also listed in the publication Pest Resistant Ornamental Plants by Deborah C. Smith-Fiola of the Rutgers Cooperative Extension Service.
Disease reactions can vary from one location to another depending on disease pressure. Cultivars with resistance may still develop symptoms under high disease pressure, but they survive black spot without much damage to the plant. It is possible for rose disease resistance to break down due to the black spot fungus adapting to the plant’s resistance, so resistance can be lost. Nevertheless, the roses listed here should perform well during most Kentucky disease outbreaks and with less fungicide than most roses.
Black spot resistant hybrid tea roses:
Canadian White Star
Love and Peace
Miss All-American Beauty
Princess of Monaco
The McCartney Rose
Black spot resistant floribunda and grandiflora roses:
City of London
Gruss an Aachen
Tournament of Roses*
Black spot resistant shrub roses: Shrub roses are normally pretty resistant to black spot disease. There are many more black spot resistant cultivars than those listed here.
All That Jazz
Katy Road Pink
Mrs. R. M. Fincn
Sir Thomas Lipton
Black spot resistant climbing roses:
Black spot resistant miniature roses:
Always a Lady
Baby Betsy McCall
Watercolor and Work of Art.
Black spot resistant Rugosa hybrid roses: Rugosa roses are normally resistant to black spot disease. These and other cultivars should do well.
Blanc double de Coubert
F. J. Grookendorst
Frau Dagmar Hartopp
Rosecraie de l’Hay
*Also resistant to powdery mildew and rust diseases.