Hello Karen,

Common lilacs, (Syringa vulgaris), are susceptible to many diseases including bacterial blight, leaf spots, leaf blight, powdery mildew and there are many insects that feed on its leaves such as lilac borer, lilac miner, caterpillars and scale. Also, lilacs prefer loose well-drained slightly acid soil. Read more here: https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=253923&isprofile=0&

https://extension.psu.edu/lilac-diseases

It is difficult to diagnose the problem from the picture—whether it is powdery mildew or a scale that is growing on the branches. A proper analysis could be done at the MSU Extension Plant and Pest Diagnostic Lab. To learn how to submit a sample, go to: https://www.canr.msu.edu/pestid/ The diagnosis will include how to treat the problem.

I hope that this helps you with your lilacs.

A certified arborist could assess the lilac. To find an arborist in your area, go to www.treesaregood.org the website of the International Society of Arboriculture.

Thank you for contacting Ask Extension.