As ubiquitous as Impatiens walleriana has been, it's hard to imagine a world without them, but it's really not looking good for this colorful standard. The villian in this tragedy is downy mildew of Impatiens, or Plasmopara obducens. It affects standard Impatiens including hybrids of I. walleriana, I. balsamina, I. pallida and the native jewelweed, I. capensis. New Guinea impatiens are resistant to the disease.
Experts in the horticulture world have provided growers with recommendations that include the use of a fungicide to prevent the disease's spread. However, even if a batch of disease-free Impatiens arrives at a retail location, there could still be contamination via windborne spores traveling more than a mile. There are also concerns about spores that overwinter in the soil.
The father of the impatiens was Claude Hope, who hybridized it in Costa Rica after WWII. His first impatiens breakthrough was the Elfin series. It was in 1966 that Hope was satisfied with the pink F1 hybrid he devised. His breeding stock consisted of hybrids and hybrid varieties from seed. The first samples of Hope's impatiens were sent as trials to Michigan State University and Purdue University. By 1969, his Elfin impatiens were introduced to rave reviews in the U.S.
The State of New Jersey Department of Agriculture has a fact sheet that explains the issue. Michigan State University Extension offers details about managing impatiens that are suspected to have the fungal disease.
Colorful alternatives to Impatiens include Begonia, Coleus, and Torenia, to name a few.