Last summer gardeners across numerous states reported an outbreak of impatiens downy mildew, a pathogen that can turn a healthy patch of impatiens diseased in short time, given the right weather conditions. The disease will infect common and double impatiens, although it appears it does not harm New Guinea impatiens or other plants.
Impatiens downy mildew thrives in cooler temperatures and moist conditions, such as an irrigated landscape bed. You’ll know the enemy by the fuzzy white spores on the underside of the leaves. Unfortunately, downy mildew can overwinter in the soil, so it looks to be a problem that won’t be going away anytime soon.
Infected impatiens will usually react with yellowing leaf and leaf curling before ultimately losing the leaf entirely. The current advice going out to gardens and yards that have been afflicted is to choose a different type of shade-loving annual, such as begonias, heliotrope, ivy geranium, sage and wishbone. Your local gardening supply store will likely have suggestions for shade-loving alternatives to the impatiens.
Good luck with your garden this spring and summer!