Peony measles is also referenced as red spot and leaf blotch. Initially, purplish-brown circular spots appear on the top of the leaves. On the underside, the spots appear brown. Over time, more spots develop and eventually merge creating large, irregularly shaped blotches. Spots can appear on the stems, flower buds, petals and seed pods as the disease progresses.
Powdery mildew can infect a variety of plants. It presents as a white-grey powder on plant material. Powdery mildew is quite common in Kansas due to the warm, humid conditions.
Fortunately, both diseases are primarily aesthetic problems unless they become severe. Promote good air flow by spacing peonies several feet apart when planting. Individual plants can be pruned selectively during the growing season to improve circulation. Powdery mildew and measles overwinter in the soil on diseased plant material. At the end of the growing season cut peonies to the ground and throw out the plant material. Do not compost, especially if the plants are diseased. Use drip irrigation, if possible, to keep water from splashing on the leaves. When leaves are wet, avoid handling them. (Cynthia Domenghini)