Shasta Daisies are Turning Black

My shasta daisies do well but the ones near by black-eyed-Susans turn black. What am I doing wrong?

You are doing nothing wrong. Disease occurs when the disease organism is present, the environment is right for the disease to occur and there is a susceptible plant. Eliminate one of the three and you eliminate the disease problem. Reduce this and other diseases by growing plants in the best possible location. Shasta daisies do best in full sun and well-drained soils. Overcrowding reduces light and air penetration and can increase disease problems. Thin overcrowded plantings or more the Shasta daisies to more suitable growing conditions. Start checking plants for problems early in the season. Remove infected leaves as soon as they appear. Clean up and destroy infected foliage in fall. Sanitation and a little cooperation from the weather may also turn this problem around.