Spruce Sawfly Larvae: Not Caterpillars, Bt Won't Work

Green "caterpillars" eating blue spruce needles in Ontario are likely sawfly larvae (not true caterpillars). Bt only kills Lepidoptera (caterpillars), not sawflies (Hymenoptera).

Control Options

1. Hand-pick: Practical on 6-ft trees. Drop in soapy water.
2. Orthene (acephate): Systemic, kills sawflies. Check Canada label availability.
3. Insecticidal soap: Direct spray on larvae—moderate effect.
4. Spinosad: Effective on sawflies, organic. Check registration.

Identification

• Sawfly larvae: 6+ pairs of prolegs (caterpillars have ≤5).
• Often feed in groups, rear up when disturbed.

Act early—defoliation weakens young trees.