Old Lilac Heavy Scale Infestation: Dormant Oil and Summer Insecticide

20-year-old lilac with gray scales on main branches, dying limbs.

Control

• Prune heavily infested branches.
• Dormant oil spray in winter (before bud break, dry, 48 hrs before frost) on all nearby shrubs.
• Now (post-bloom): use malathion for crawlers. Follow with insecticidal soap if needed.
• Multiple applications likely necessary.

Heavy infestation can kill the plant.