I’ve heard several local reports of major problems with downy mildew on Impatiens in the landscape. In fact this seems to be widespread not just in our area but also down the West Coast and even on the lower East Coast.
The problem is the weather. It’s perfect for downy mildew. There doesn’t seem to be a good solution to the problem. By the time the disease is spotted, it’s already making good headway and is proving difficult to stop.
Here’s an in-depth article on the topic written by 2 Extension Agents on the East Coast: http://ow.ly/8VlOE