Cotton Defoliation

Timing and Methods:

• 60 to 75% open bolls (only 60 for uniform crop)
• NACB (Nodes Above Cracked Boll) – 4 or less (around 3 days per node)
  • Locate uppermost 1st position cracked boll, count up to uppermost harvestable boll (BOLL FOR HARVEST, NOT NECESSARILY UPPERMOST)
• Sharp Knife – cotton strings when boll is cut –Seed are fully developed (brown coat & cotyledons)
  • Mature bolls difficult to cross-section
  • Tan to brown seed coat correlates with mature boll
  • Fiber should “string”

Harvest Aids:

• Two general types:
  • Herbicidal defoliants
  • Hormonal defoliants
• Both cause the release of ethylene and assist in leaf defoliation
• 20 GPA is best
• Herbicidal Defoliants
  • Tribufos (Folex)
    • Injures leaf below the cuticle, causing stress which stimulates ethylene production
  • PPO INHIBITBITING HERBICIDES
    • Carfentrazone (Aim), Pyrafluefen ethyl (ET)
      • Destructs cell membranes, causing ethylene production
    • Flumiclorac (Resource)
    • Flutiacet-methyl (Blizzard)
• Hormonal Defoliants
  • Ethephon (Prep, etc.)
    • Increases production of ethylene, leading to leaf drop
    • Excellerated boll opening
      • Finish 6 Pro – ethephon + cyclanilide
      • FirstPick – ethephone + urea sulfate
  • Thidiazuron (Freefall)
    • Enhances the production of ethylene and inhibits auxin transport
    • Inhibits regrowth
      • Ginstar – thidiazuron + diuron

Rain-free Requirements:

• Tdz – 24 hours
• Ginstar – 12 hours
• Aim – 8 hours
• Display – 8 hours
• Ethephon – 6 hours
• Finish – 6 hours
• Folex – 1 hour
• Et – 1 hour
• Sharpen – 1 hour
• Paraquat – 30 min.