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Powdery Mildew

My lilac had a grayish blight on the leaves this summer. What caused this and how can I prevent it?

Your lilac had powdery mildew, a common fungal disease. It occurs in late summer in humid weather, especially if your plant is located in a damp, shady area. While unsightly, it does not damage the plant since it only affects the outermost leaf cell layer. If it really bothers you, spray the leaves with a sulfur fungicide early in the season. If mildew appears late in the season, spray again.

Newer varieties of lilac are more disease resistant than the common lilac. Improving air circulation by pruning out any dead branches will also help to reduce mildew, advises Joan Barczak, owner of Blumen Gardens, Sycamore.


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