Lilac/Ash Borer in Lilac Tree: Permethrin Spray Timing

Orange grub with black head, 1.5", hard skin, tunneling in lilac branches—ash/lilac borer (Podosesia syringae).

Life Cycle

• Larvae overwinter in tunnels.
• Adults (wasp-like clearwing moths) emerge mid-April–early July.
• One generation/year.

Control

• Pheromone traps to time sprays (spray 7–10 days after first catch).
• Phenology: Spray when Vanhoutte spirea in full bloom (~May 1).
• Second spray 4 weeks later.
• Product: Permethrin (Hi-Yield Garden, Pet, & Livestock Insect Control) — only homeowner product listing this borer on label.

Sanitation

Remove/cut heavily infested canes in fall/winter. Burn or dispose.