Spring cleaning is continuing at my house—more specifically in my garden. I’ve pruned my rose bushes and applied the first fertilizer of the season. I also took the time to rake out all of the old mulch around my roses.
Black spot is a common fungal disease that can affect roses across the state. Sanitation is the first step in controlling black spot. Leaves that appear to be infected should be removed and disposed of properly throughout the year. You should do this throughout the growing season. But since the fungus overwinters on diseased leaves and canes, you should intensify your efforts near the end of the growing season.
You may need to prune canes severely in the spring prior to new growth. In addition, remove and replace mulch beneath diseased plants.
The Extension System has an excellent rose publication. It recommends a dormant spray of liquid lime-sulfur at the time of leaf emergence. The best results will be obtained if the plants and ground are sprayed after the old mulch is removed and before fresh mulch is applied.
Good control of black spot can be achieved with a regular fungicide spray program. I have learned that I do not really have the time to devote to a spray regimen.
Dr. Raymond Kessler and I talked recently about roses. After visiting with him, I have decided that installing more disease resistant plants are a better choice for my garden.
You can hear Dr. Kessler on Backyard Wisdom in early April discussing both rose selections and how to care for them.