Impatiens Downy Mildew
Gardeners in the US may not be able to purchase the common garden impatiens (impatiens walleriana) for their shade gardens this year. That is because a destructive fungus has attacked them in nurseries and landscapes in 33 states. The fungus is commonly called downymildew which is different from other kinds of plant mildews. Downy mildew causes complete defoliation or plant collapse, especially in landscape plantings under moist conditions and cool nights. (see here)
Though a relatively recent problem in the US, European gardeners have been dealing with this problem for several years since it can overwinter in the soil.
This GardenLady has decided to plant begonias where I planted impatiens in previous years. I would not trust the impatiens in stores even if I were to see them for sale- though most nurseries are not going to even risk selling them this year. (see here)
There are many other shade loving plants one can substitute for impatiens. Caladiums are another one of my favorite choices.
There are still some impatiens that are not affected by downy mildew such as: New Guinea impatiens (Impatiens hawkeri) (see here)