Answer: Powdery mildew is the most common disease of gerbera. Infection may start on the lower foliage and escape early detection if plants are not periodically monitored for this disease. Powdery mildew pathogens are readily disseminated in the air by air currents. Conditions that favor the development of powdery mildew diseases are moderate temperatures with high humidity. Some powdery mildew pathogens are enhanced by fluctuations between warm and cool temperatures but a relative humidity of 85% is generally needed for disease to develop.
Fungicides can be effective in managing powdery mildew diseases but take care to initiate applications at the first sign of infection and to rotate among effective fungicides. Include a systemic fungicide in the spray rotation.
Gerbera daisies are perennial in NC. The foliage will die down this winter but fresh new foliage will sprout when the weather warms up in the spring. You can lessen the chance of reinfection by removing all the leaves and stems when they die back. Make sure your plants have adequate air circulation all around to further discourage outbreaks of powdery mildew.
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