Lilac leaf problem
Thank you for your question. You did not indicate your location, and I have no idea what pests of lilacs are in your area. Here is a description of a common pest in the States with similar leaf damage: https://ask.extension.org/questions/152235 Perhaps you can find a horticulture resource in your region who is familiar with insects near you. Good luck!
Thank you for your timely response. I will try the spray
I haven't had any luck with local information sites