Peony Blight Peony Blight Botrytis blight is the most important disease of peonies in Nebraska. This disease affects buds, stems, and leaves. Young shoots in all stages of growth, up to and including the buds may suddenly wilt and fall over. Examination reveal a soft, brown to black rot of the stem that may extend down to, and in some instances, below the surface of the soil. Infected small buds stop growth and turn black.
Older buds turn brown and fail to open and often the petals become watery and matted.
The stalk for several inches below the infected flowers is usually killed. The leaves are usually attacked later than other parts of the plants. Large, irregular spots with dark and light brown coloring appear. These spots vary considerably in size and may involve the entire leaflet. Boytrytis blight is caused by a fungus which lives from one season to the next on old diseased foliage.