|The fungus Diplocarpon rosae or "black spot" can infect first-year |
rose canes with the right wet conditions, even during
North Carolina winters. Photo by J.S. Corser, Durham Co. EMG.
Prevention & Treatment: The spread of black spot can be reduced and future infections minimized by following these cultural practices:
- Plant Resistant Varieties: (See the following list)
- Maintain Good Sanitation: Sanitation practices are critical in reducing future disease development. In the fall or winter remove all old leaves on the ground along with any mulch that has been contaminated with infected leaves. Replace with a fresh layer of mulch before new rose growth begins in the spring.
- Remove & Destroy Infected Canes: Canes affected by black spot have dark or reddish areas (lesions). Severely infected plants should be pruned back in the winter or early spring to within 1 to 2 inches of the bud union, according to variety and cultivar. During the growing season, remove and dispose of infected leaves as they appear.
- Keep Leaves Dry: It is best not to syringe plants with water, and do not use overhead irrigation, especially not in the late afternoon or early evening. Soaker hoses are an excellent way to water roses and to conserve water. Promote rapid drying of leaves by planting roses in the full sun. Space new plants far enough apart to allow for good air circulation.
Black Spot - Resistant Roses:
- Hybrid tea: ‘Pride N Joy’
- Floribunda: ‘Sexy Rexy’
- Grandiflora: ‘Prima Donna’