Mechanical induction: drilling, tapping, wound management

1. Concept & Theory

Mechanical induction is the practice of creating controlled wounds in Aquilaria trees to stimulate their natural defense response, which triggers resin biosynthesis.

Mechanism:

  • Wounding damages plant tissue → tree perceives it as stress/infection → activates defense pathways.
  • Defense response includes production of secondary metabolites like sesquiterpenes and chromones, forming resin.
  • Mechanical induction is often used alone or in combination with fungal or chemical inoculants to accelerate resin formation.

2. Methods of Mechanical Induction

  • A. Drilling
    • Description: Create small holes in the trunk using a hand or motor drill.
    • Hole size: 1–2 cm in diameter, 5–15 cm deep depending on tree size.
    • Spacing: Vertically and horizontally spaced 30–50 cm apart to avoid excessive stress.
    • Purpose:
      • Initiates resin around wound.
      • Can serve as a site for fungal or chemical inoculation.
  • B. Tapping / Chiseling
    • Description: Carve or chisel grooves into the trunk surface to create shallow wounds.
    • Techniques:
      1. Vertical grooves along the trunk.
      2. Cross-shaped incisions for better resin flow.
    • Depth: 0.5–2 cm for surface tapping; deeper chiseling for injection sites.
    • Purpose: Induces localized resin formation; allows manual resin collection in some cases.
  • C. Bark Removal
    • Description: Strip small sections of bark around the trunk.
    • Purpose: Exposes cambium layer → stimulates defense response → faster resin accumulation.
    • Caution: Avoid removing too much bark → can kill the tree.

3. Wound Management

Proper wound management is critical for tree health and resin quality.

  • A. Sealing
    • Seal wounds with sterile cotton, paraffin wax, or tree wound paste to:
      • Prevent contamination (fungi, bacteria)
      • Retain moisture for optimal resin formation
  • B. Healing Support
    • Apply organic fertilizers or compost teas to support recovery.
    • Maintain soil moisture to reduce stress.
  • C. Rotation
    • Avoid wounding the same area repeatedly.
    • Allow previous wounds to heal before new mechanical induction nearby.

4. Advantages of Mechanical Induction

  • Simple, low-cost, does not require laboratory facilities.
  • Can be applied to large numbers of trees in plantations.
  • Works as a standalone method or in combination with fungal/chemical induction for higher yield.

5. Limitations / Risks

  • Resin quality may be lower than naturally infected trees if used alone.
  • Over-wounding can kill the tree or reduce growth.
  • Requires skilled labor to optimize depth, spacing, and frequency.
  • Tree response is slower than dual-action fungal + chemical methods.

6. Best Practices

  1. Use mechanical induction in combination with fungal or chemical inoculants for higher yield.
  2. Space wounds properly (30–50 cm apart) to avoid stress concentration.
  3. Monitor tree response every 3–6 months.
  4. Maintain tree health with organic fertilization and irrigation.
  5. Seal wounds promptly to prevent contamination.