Thanks to a cool, damp spring, Impatiens Downy Mildew has made its way to the Kansas City Area. While our crop remains free and clean of this issue, others are seeing total losses in the landscape already this season. This fungal disease only infects Impatiens walleriana, also known as our common bedding impatiens. New Guinea Impatiens and Sunpatiens and other types of annuals are not affected.
Impatiens Downy Mildew normally starts with just a few leaves looking stippled or light yellow, becoming all yellow over time. You may notice some gray markings on some of the top side of the more yellow leaves, but even more so on the underside of the green leaves. In the more advanced stages, the gray undersides will look fuzzy or ‘downy’, and leaves will drop leaving bare stems.
Our recommendation is to remove all Impatiens in the affected bed as soon as you notice the issue. You should no longer plant Impatiens walleriana in that space. The spores will be in the soil and continue to reinfect subsequent plantings. Replant the area with non-susceptible plants, such as Torennia, Browalia, Begonia, upright Fuchsias, New Guinea Impatiens, or Sunpatiens.