Wallerianas are the Species of Impatiens we all have held dear to our hearts for many decades as the "go to" plant for our shady garden, with dozens of colors to chose from.
About 8 years ago they were attacked by a new strain of Downey Mildew, called Impatiens Downey Mildew IDM for short. IDM would devastate a bed within a few days. Plants would drop all their leaves, leaving only stems showing.
THERE IS NO CURE
Most comercial growers stopped growing them altogether.
Beacon Impatiens have been bred to be resistant, if not impervious to IDM.
Researchers inoculated Beacons with IDM over and over and they never contracted the disease.
For 2020 there are only 5 seperate colors, with more being developed.