Protect Your Roses from Black Spot Disease
Black Spot is a fungal disease that attacks roses in many parts of the United States, targeting young leaves and newer canes. Here are some tips to limit this problem in your rose garden.
- Choose your rose varieties with disease resistance in mind. Thoughtful breeding has expanded the selection and there are now a wide range of bloom colors, flower forms, bush size and rose classifications (shrub, hybrid tea, miniature, etc.) available with disease resistant traits.
- Site your plants in locations that get 6 to 8 hours of sunlight. Early day sun is especially valuable because it helps to dry dew from foliage. Wet leaves are more prone to fungal diseases.
- Find a section of the garden that enjoys plenty of air circulation. Avoid back corners and places where structures and plant congestion limits air movement.
- Make sure that your garden provides roses good soil. Rich, healthy soil produces stronger plants that are less likely to succumb to disease.
- Prune your roses. Pruning is done both to shape plants and to open up the centers for improved air flow. Roses that have been pruned to control dense growth have more leaves exposed to the sunlight, which increases photosynthesis and therefore, food production for the plant. Good circulation helps dry foliage readily so fungal spores are less likely to have the several hours of moisture needed to germinate.
- Mulch the soil below your rose plants. This reduces competition from weeds and helps maintain soil moisture. Also, having the bare soil covered with mulch keeps soil-borne disease spores from splashing on the roses’ foliage.
- If black spot occurs, trim off diseased foliage and discard. Do not add to your compost pile or bin. Compost contaminated with disease spores can spread the infection throughout your garden in subsequent seasons. Treat the plant with an organic fungicide such as Revitalize Biofungicide. This product is also an excellent preventative when used to kill overwintering spores in early spring, before the rose buds swell.