Bringing Life Back To My Lilac Bush?

You may want to feed them plant food with acid in it,like twice a week then once a month for about3or4months.Then next year they may do something.But you may want to do this A.S.A.P.
Good luck I hope you did not kill the roots.

I had it too and took a branch to a nursery. They told me it was insects and I sprayed it with dish hand detergent mixed with a little water. I sprayed it liberally. Now in full bloom and nothing white on branches. If it occurs again I will spray again. It happened two years in a row after blooming season. No plants around it had the white stuff ever.