Powdery Mildew

Question: I have a pink lemonade honeysuckle vine. It has bloomed all summer, but the leaves are turning a powdery white and falling off. Is there a remedy to save my plant?

Answer: Powdery mildew is the name for the grayish-white powdery coating caused by a fungus growing on plant leaves, shoots and flowers. This disease is caused by a group of similar fungi that attacks a wide variety of plants, including lilac, beebalm and honeysuckle. 

Although plants infected with powdery mildew rarely die, the disease can reduce the attractiveness of landscape ornamentals. 

Conditions, including high humidity, overcast weather, warm days and cool nights favor powdery mildew development. The disease is common in crowded plantings and in areas with restricted air movement. Recommendations to reduce infection include adequate spacing between plants and choosing the right plant for the right location so as to make conditions less favorable for the disease.

There is no cure for infected plants, however, preventative fungicide sprays will help protect healthy plant tissue from infection. Products containing active ingredients, such as chlorothalonil, triforine and sulfur, are labeled for control of powdery mildew. Hosts and diseases listed on specific product labels may differ between products containing the same active ingredient, thus be sure to read the label.

At the end of the growing season, remove powdery mildew-infected leaves from the ground to reduce carryover of the mildew fungi into the next season.

-Beverly Shaw, Advanced Master Gardener Purdue University