Possibly Lilac blight. This is encouraged by the kind of spring weather we have had.
Dark black streaks form on one side of young shoots. The flowers wilt and turn brown and unopened flower buds become blackened.
If your lilac bush does have infection, prune and burn all infected parts as soon as you notice them. A spray of a copper-based pesticide, which is organic, during the early spring each year should help prevent the problem before the buds begin to break.

Thank you so much.