Powdery Mildew of Lilac

Disease Information

Powdery Mildew

Symptoms and damage

Lilac trees are quite susceptible to the fungus that causes powdery mildew. Affected foliage slowly becomes covered with a white powder-like coating that is easily brushed away. Older leaves at the bottom of the tree are usually affected first, around July. If left untreated, powdery mildew will spread throughout the tree and eventually cause the leaves to yellow and drop before the end of the growing season.


1-Prune the lilac in spring immediately after blooming to remove old, dead branches and increase air circulation. Poor air circulation exacerbates powdery mildew. Because the entire bush is likely infected, pruning out diseased branches is not practical.

2-Spray lilac bushes with a fungicide labeled for treating mildew as soon as symptoms appear.

3-Repeat the fungicide application in two weeks, or as directed by the manufacturer.

Examples of Fungicides(Myclobutanil - Neem Oil – Propiconazole - Thiophanate-methyl )


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