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Downy Mildew on Impatiens

Posted: August 24, 2012

This fungal disease is a fairly new problem which has cropped up on garden impatiens this summer, causing almost complete defoliation of plants, leaving just bare stalks as a reminder of what was once a beautiful plant.

Early symptoms include foliage that turns a lighter yellow-green, stunted growth, and poor flowering, followed by downward curling of the leaves and a whitish-gray powdery fungal growth on the underside of leaves. Leaves and flowers then drop, resulting in bare stems, which can then get soft and collapse if weather conditions stay cool and moist. The disease is much less of a problem during hot and dry conditions.

If your impatiens are infected, it’s too late to spray a fungicide to control the disease. Remove infected plants and fallen leaves. Researchers are not yet sure if this fungus overwinters in our region; but if you have had problems this year, it’s recommended to plant or interplant with alternative plants next year, such as New Guinea impatiens, which are highly resistant, begonias, or coleus.

By Annette MaCoy, Horticulture Educator