What to watch for
•Inspect the undersides of the leaves regularly for signs of disease. (Powdery mildew is a different pathogen and can be seen on the top of leaves.)
•At the first sign of the disease, the plants should be removed, roots and all, sealed in a plastic bag and carefully disposed of. There is no cure for downy mildew, and the progression of the disease can't be stopped.
•Never compost a diseased plant.
•Remove any impatiens plant material, including dropped leaves, from the garden.
•Do not attempt to plant impatiens in that spot again. Spores can live in the soil.
If not impatiens, what?
•There are a number of shade annuals that can bring color to the garden. Perhaps it is time to experiment with something new.
•Begonias, coleus, caladiums, heliotrope, sweet potato vine, lobelia, sweet alyssum, salvia, wishbone flower or oxalis are colorful substitutes. And New Guinea impatiens can do well in the shade, if they get sun during some part of the day. And this cousin to the garden impatiens is mildew-resistant.