It’s the time of year when two fungal diseases may appear on peony plants. Preventative care each year is the best control against them.
Peony measles, also referenced as red spot and leaf blotch, appears initially as purplish-brown circular spots on the top of the leaves. The spots on the undersides of the
leaves are 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.
