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Plant NameTypeDescription 
Downy mildewImpatiensDiseaseDowny mildew of impatiens is a disease affecting the standard garden impatiens, Impatiens walleriana, and its cultivars and hybrids. The disease is caused by a fungus-like organism which survives in plant debris and infested soils. The disease develops and spreads rapidly when conditions are favorable (wet foliage, cool temperatures, and humid air). Downy mildew symptoms may initially appear as mottling, stippling or yellowing of infected leaves, usually beginning on the youngest leaves and shoot tips. The margins of affected leaves may curl downward. Seedlings are especially susceptible to damage, and plants infected early in development may be stunted. Symptoms of downy mildew may be mistaken for other problems such as nutrient deficiency or root rot. During cool, humid conditions, a downy or moldy-looking white growth may develop on the underside of leaves. Infected leaves and flowers drop from the plants, often leaving only a bare stem with a few leaves or flowers remaining at the tip. As the disease progresses, plants will become completely defoliated, collapse, and die. The disease is spread easily from infected plants by air or water movement. While all varieties and hybrids of I. walleriana are susceptible, New Guinea impatiens (I. hawkeri) is highly tolerant of the disease.