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Paraquat and glufosinate ammonium (non-selective contact herbicides)

Paraquat dichloride 24% SL and glufosinate ammonium 13.5% SL are the two main non-selective contact post-emergence herbicides used in India for bund and inter-row weed knockdown in cotton, orchards and plantation crops. Both are foliar contact only — they do not move systemically and are safer for in-crop directed use than systemic Glyphosate Orchard Warning.

Composition / Active ingredient

  • Paraquat dichloride: 24% SL — Dhanuka Ozone, Syngenta Gramoxone and generics
  • Glufosinate ammonium: 13.5% SL — UPL Sweep / Sweep Power, Bayer Basta

Mode of action

The two molecules act through different but equally rapid mechanisms:

  • Paraquat is a bipyridylium that diverts electrons from Photosystem I, generating superoxide and hydrogen peroxide free radicals that destroy cell membranes within hours. HRAC Group 22.
  • Glufosinate inhibits glutamine synthetase, the only plant enzyme that detoxifies ammonia. Ammonia accumulates, photosynthesis stops and the foliage desiccates over 3-7 days. HRAC Group 10.

Both molecules are contact-acting only; they do not translocate beyond the treated leaf area.

Target use and dose

Cotton and orchard bund knockdown is the primary Indian use. Paraquat is sprayed at 800-1200 ml/acre as a directed spray with hood; glufosinate (Sweep Power) at 1.32 L/acre (~250 ml/acre in foam-based application; see Upl Sweep Power Glufosinate). Both must be shielded from the crop canopy by hood or foam applicator.

Safety and regulatory status

Paraquat is classified as highly hazardous by PAN International and is restricted in Kerala (and banned in many countries); CIBRC currently retains registration on nine crops with stringent label requirements. There is no antidote for paraquat poisoning. Glufosinate is comparatively safer for operators but is itself under regulatory review in the EU. Both are toxic to non-target plants; drift must be avoided.

See also: Upl Sweep Power Glufosinate, Glyphosate Orchard Warning, Pendimethalin Cotton Preemergent, Agil Propaquizafop Cotton.

References

  1. Ozone — Paraquat 24% SL. Dhanuka Agritech.
  2. UPL Sweep Power — Glufosinate 13.5% SL. UPL India.