Powdery Mildew on Ninebark
I have a Center Glow ninebark bush that is going into its second year. It developed powdery mildew on some of the leaves. It was originally located on the south side of the house next to a retaining wall. I have since moved it more into the open. Is this enough to control the problem?
I have seen quite a bit of powdery mildew on ninebark this spring. The weather conditions have been right for this disease to occur. A change of weather and the right growing conditions will reduce future problems. Provide adequate air circulation by properly spacing and locating plants, as you did, to reduce the risk. Whenever possible grow ninebarks and other powdery mildew susceptible plants in full or morning sun. Fortunately a healthy plant can tolerate the damage. If you decide to treat, try one of the eco-friendly fungicides like Neem or the Cornell baking soda mix. Cornell University found baking soda helped suppress powdery mildew. Mix one tablespoon baking soda plus one teaspoon insecticidal soap OR lightweight horticulture oil (these serve as a spreader sticker) in a gallon of water. Repeat applications of this or commercial fungicides are needed throughout the season to protect the uninfected foliage.