Chemical group and mode of herbicide action
Pyrazosulfuron Ethyl belongs to the sulfonylurea chemical family and functions as a systemic herbicide absorbed primarily by weed roots and emerging shoots.
Inside the weed, it inhibits acetolactate synthase (ALS, also known as AHAS), a key enzyme essential for synthesizing branched-chain amino acids (valine, leucine, and isoleucine). This halts cell division and root elongation within hours of application.
- Chemical family: Sulfonylurea (ALS/AHAS enzyme inhibitor).
- Systemic mobility: Absorbed rapidly by roots and foliage and translocated throughout growing weed points.
- Low active ingredient load: Delivers reliable weed suppression at extremely small quantities of active ingredient per hectare.
Weed spectrum and application timing in rice
The product is registered for weed control in transplanted paddy as well as wet direct-seeded rice (DSR).
It controls problematic wetland sedges such as Cyperus difformis and Cyperus iria, alongside broadleaf species like Ludwigia, Sphenoclea, and Monochoria vaginalis.
- Application window: Applied between 3 to 8 days after transplanting or direct seeding when weeds are at the 1 to 2 leaf stage.
- Key sedges controlled: Cyperus difformis, Cyperus iria, and Fimbristylis miliacea.
- Broadleaf weeds controlled: Ludwigia parviflora, Sphenoclea zeylanica, and Eclipta alba.
Water management and field application techniques
Proper water management is critical to activating Pyrazosulfuron Ethyl and ensuring residual weed suppression in the rice field.
Farmers typically apply the wettable powder either as a foliar spray or by broadcasting mixed with dry sand or urea fertilizer into standing water.
- Water depth: Maintain 3 to 5 cm of standing water in the field during application and for 4 to 5 days thereafter.
- Uniform distribution: When broadcasting with sand or urea, ensure even dispersal across the entire plot.
- Precaution: Do not submerge rice seedlings completely; drain excess floodwater before application if necessary.
Official source
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ICAR - National Rice Research Institute ↗Related on KisanPe
Common questions
When should Pyrazosulfuron Ethyl 10% WP be applied in rice fields?
It is best applied between 3 to 8 days after transplanting or direct seeding, when weeds are at the 1 to 2 leaf stage.
What weed types does Pyrazosulfuron Ethyl control?
It specifically targets sedges (Cyperus spp.) and major broadleaf weeds in paddy fields, along with some annual grasses.
Is standing water necessary when applying Pyrazosulfuron Ethyl?
Yes, maintaining 3 to 5 cm of standing water during application and for several days after helps optimize weed control.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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