Image by Rasbak
By Nikki Phipps
(Author of The Bulb-o-licious Garden)
If your rose leaves have black spots, it may be suffering from Black Spot, one of the most common fungal diseases affecting rose bushes. Let’s look at what causes black spots on rose bush leaves and steps for treating black spot roses.
What Causes Black Spots on Rose Bush Leaves?
Many frustrated gardeners wonder “what causes black spots on rose bush leaves?” Black spot and roses usually go hand in hand. In fact, many roses get a little black spot, which can even be tolerated to some degree without any harm to plants. However, heavy infections can seriously defoliate plants.
Rose black spot is caused by fungus. Dark-brown to black leaf spots develop on the upper leaves, which eventually become yellow and drop.
Black spot can be distinguished from other leaf spot diseases by its fringed edges and dark black color. Raised, reddish-purple spots may also appear on rose canes. Warm, humid conditions favor its germination and growth.
Black Spot Rose Disease Control
Treating black spot roses begins with prevention. Black spot rose disease control includes adequate planting sites, the use of resistant cultivars, and pruning. Roses should be planted in areas with plenty of sunlight and good circulation.
Good garden hygiene is important for treating black spot roses. During the growing season, overhead watering should be avoided. Removal of leaf litter and pruning of diseased canes (back to healthy wood) is also important.
Fungicides can also be applied to keep this disease under control but should be done as a last resort. Neem oil can also be used, which helps control many rose pests as well.
Another popular method includes spraying a solution of baking soda and water on foliage. Baking soda helps change the pH level on leaf surfaces, which makes it more difficult for black spot to infect plants. To make this organic solution, mix a couple tablespoons of baking soda with a gallon of water. To help keep the baking soda on the leaf, add a drop or two of bleach free dish soap. Spray both side of the foliage. Reapply weekly and repeat after any rain.
When your rose leaves have black spots, you have options for treating the problem. With a little patience, your roses can return to full beauty.