Answer: You may be dealing with verticillium wilt, a fungal disease. Vascular wilt is a troublesome disease of impatiens, especially in beds that have been planted to impatiens for many years. Control of this disease is difficult since the pathogen is commonly found in soil. One of the key strategies for control of vascular wilts is prevention. Therefore, it is important to avoid planting in infested soil. It is also helpful to maximize plant vigor by good cultural care and watering. Careful handling of plants will avoid root injury which enables the fungus to enter the plant. Since repeated use of the same area greatly increases the amount of disease, rotation is essential. When available, it is also helpful to use resistant varieties. Chemical controls are not effective for these fungi. I'd try planting them in a different bed for a year or two, or planting them in containers.
Best wishes with your impatiens!
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