Bagworm Control Timing and Insecticide Selection for Central Indiana

Blue spruce infested with bagworms in Central Indiana (north of Indianapolis). Owner has 15-gal sprayer, needs precise timing and current product recommendations.

Regional Timing

Central Illinois/Indiana: egg hatch = early to mid-June. Optimal spray window = 2 weeks post-hatch (late June). Second application 1–2 weeks later catches late hatchers.

Dispersal Mechanism

Newly hatched larvae "balloon" on 2–3 ft silk threads, drifting on wind to new hosts. Explains sudden appearance on isolated trees.

Effective Insecticides (Current)

• Bacillus thuringiensis kurstaki (Dipel, Thuricide): Must be ingested; thorough coverage essential. Best on young larvae.
• Spinosad (Conserve, Ferti-lome): Contact + ingestion; very effective.
• Cyfluthrin (Tempo, Bayer products): For larger larvae; thorough coverage required.

Critical Threshold

Bags >¾ inch = difficult to control. Early detection (June) is everything. Hand-pick if feasible on small trees.