The fungus that causes Hollyhock rust (Puccinia malvacearum) can be transmitted into the garden by wind or infected transplants. Once the fungus has entered the garden it can be further spread by splashing water. The fungus thrives in warm, humid conditions and can overwinter in plant debris.
To avoid introducing this disease into the landscape carefully inspect plants before bringing them home. Monitor plants throughout the growing season to catch early signs of the disease for most effective control. In the fall remove all hollyhock stalks, leaves and debris and destroy them as a proactive measure against overwintering the fungus. Keep area weed-free to remove host plants. If symptoms of rust are present during the growing season, remove infected foliage and dispose of it. Protect healthy leaves using a fungicide such as sulfur or myclobutanil (Spectracide Immunox or Fertilome F-Stop Lawn and Garden Fungicide). Sulfur may burn leaves if the air temperature is over 85 degrees F within 24 hours of application. Follow label directions for timing and rate. (Cynthia Domenghini)