Chemical Class and Photosystem I Disruption
Paraquat Dichloride 24% SL belongs to the bipyridylium class of herbicides. It operates as a Photosystem I (PSI) electron divertor (WSSA Group 22 / HRAC Group D) in green chloroplast thylakoids.
Upon leaf contact, the divalent paraquat cation intercepts electrons from ferredoxin in the photosynthetic light reaction, generating reactive superoxide radicals and hydroxyl ions. These free radicals rupture lipid cellular membranes, causing complete desiccation within hours of sun exposure.
- Active ingredient: Paraquat Dichloride 24 percent w/w SL (Soluble Liquid)
- Herbicide group: WSSA Group 22 / HRAC Group D (Photosystem I electron divertors)
- Action mode: Non-selective, ultra-rapid contact desiccation with zero xylem translocation
- Inactivation: Binds irreversibly to soil clay minerals, becoming biologically inactive upon ground contact
CIBRC Approved Target Uses and Crops
The Central Insecticides Board registers Paraquat Dichloride 24% SL strictly for designated agronomic uses where non-selective foliar burndown is required without leaving chemical residues in the root zone.
Because it binds strongly to soil clay particles, it leaves zero residual soil activity, enabling subsequent crops to be planted once weed foliage has desiccated.
- Tea: Directed post-emergence weed control between tea bush rows avoiding crop foliage
- Potato: Post-emergence potato haulm desiccation 10 to 14 days prior to tuber harvesting
- Rubber & Coffee: Inter-row clearing of competitive grasses and annual broadleaf weeds
- Cotton: Pre-harvest defoliation and directed inter-row weed suppression using shielded spray hoods
Statutory Precautions, Toxicity, and Safe Handling
Paraquat Dichloride is a hazardous compound carrying a statutory blue/yellow toxicity warning triangle. It has no known chemical antidote; ingestion or concentrated dermal exposure can lead to fatal pulmonary fibrosis.
Commercial formulations in India include stenching agents (odorants), emetics, and blue dyes to prevent accidental ingestion. Applicators must wear full personal protective equipment and utilize shielded spray hoods.
- Built-in deterrents: Formulated with strong emetics, warning dyes, and bitter stenching agents
- Protective equipment: Mandatory chemical-resistant gloves, apron, boots, and face shield
- Spray hood: Use hooded drift-reduction nozzles to prevent spray drift onto non-target crops
- Storage restriction: Store locked away in original containers; never decant into beverage bottles
Official source
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Central Insecticides Board and Registration Committee (CIBRC) ↗Related on KisanPe
Common questions
What makes Paraquat Dichloride act so rapidly compared to Glyphosate?
Paraquat is a contact desiccant that generates free radicals rupturing cellular membranes within hours of sun exposure, whereas Glyphosate is a systemic enzyme inhibitor requiring 7 to 14 days.
Does Paraquat remain active in the soil to kill germinating weed seeds?
No, Paraquat is adsorbed and inactivated almost instantly by clay minerals and organic matter in the soil, leaving zero residual herbicide activity.
Why is Paraquat used for potato haulm destruction?
Applying Paraquat to mature potato vines rapidly desiccates the green haulms, facilitating skin hardening of the tubers and easing mechanical harvest operations.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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