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Mepiquat chloride growth regulator in cotton

Mepiquat chloride is a synthetic plant growth regulator that inhibits the late stages of gibberellin biosynthesis, suppressing vegetative growth in cotton and redirecting photosynthetic assimilates from leaves and stems to bolls. It is the most widely used PGR in commercial cotton cultivation in India and globally.

Composition

  • Active ingredient: mepiquat chloride
  • Common Indian formulation: 5% aqueous solution (5% AS), marketed as Gharda Chamatkar and equivalents from other registrants
  • Regulatory status: registered with the Central Insecticides Board and Registration Committee (CIB&RC) under the Insecticides Act 1968
  • Other formulations available globally: 4.2% SL, 25% SC

Mode of action

Mepiquat chloride inhibits the activity of ent-kaurene oxidase and other enzymes in the gibberellin biosynthetic pathway. The resulting low endogenous gibberellin level shortens internode length, thickens stems, reduces leaf area expansion and slows the canopy build-up. The same hormonal shift reduces shedding of squares and young bolls and improves the relative proportion of fruit-bearing branches to vegetative branches. Properly timed application also improves canopy light penetration and pesticide spray coverage.

Target use and dose

Standard recommendation for Indian cotton:

  • Concentration: 5% AS at 400-600 ml per acre in 200-400 litres of water.
  • Timing: split applications beginning around 45-60 days after sowing, with one or two follow-up sprays at 10-15 day intervals depending on vegetative vigour.
  • Avoid: moisture-stressed or weak crops; application to a stressed canopy further suppresses growth and reduces yield.

ICAR-CICR recommends adjusting dose and number of splits to vegetative status, with low-vigour crops receiving lower rates or being skipped.

Safety and regulatory status

CIB&RC-registered for cotton; non-toxic to honey bees and most non-target organisms at recommended doses. Pre-harvest interval is specified on the label. Spray equipment should be rinsed thoroughly because residues can affect subsequent sensitive crops.

See also: Gibberellic Acid Ga3, Ethephon Pineapple Flowering, Cotton Biostimulant Flower Retention.

References

  1. Gharda Chamatkar Mepiquat Chloride 5% AS. Gharda Chemicals.
  2. Plant Growth Regulators in Cotton. Oklahoma State University Extension.