Active Ingredient and Sulfonylurea Chemistry
Pyrazosulfuron-ethyl belongs to the sulfonylurea chemical group (HRAC Group 2), functioning as an acetolactate synthase (ALS) inhibitor.
It blocks the biosynthesis of essential branched-chain amino acids (leucine, isoleucine, and valine), arresting cell division in weed roots and shoots within hours of uptake.
- Active Ingredient: Pyrazosulfuron-ethyl 10% WP (Wettable Powder)
- Low Dose Efficacy: Highly active at exceptionally low grams-per-acre application rates
- Dual Translocation: Rapidly absorbed through both weed roots and foliage, moving acropetally and basipetally
Target Weeds and Rice Applications
Chempa is labeled for transplanted rice, wet direct-seeded rice (DSR), and rice nursery beds.
It suppresses difficult sedge complexes and broadleaf weeds before they can establish competitive root networks.
- Sedges Controlled: Cyperus iria, Cyperus difformis, and Fimbristylis miliacea
- Broadleaf Weeds: Ludwigia parviflora, Sphenoclea zeylanica, Eclipta alba, and Monochoria vaginalis
- Application Window: Applied at 3 to 7 days after transplanting when weeds are germinating or at 1 to 2 leaf stage
Application Method and Water Management
Maintain a shallow standing water depth of 2 to 3 cm in the paddy field during application and for 3 to 4 days thereafter to sustain the herbicidal barrier.
Chempa can be applied through foliar sprayers or mixed with dry sand and broadcast evenly across standing water.
- Broadcast Method: Mix recommended dose thoroughly with 15 to 20 kg of dry sand or fertilizer per acre and distribute uniformly
- Spray Method: Dissolve in 150 liters of water per acre using a floodjet or flat fan nozzle
- Water Maintenance: Prevent field drying immediately after application to ensure uniform root zone activation
Official source
Check the latest rules, benefits and forms here. KisanPe is an independent platform and is not a government website.
Central Insecticides Board & Registration Committee ↗Related on KisanPe
Common questions
What is the chemical composition of Chempa herbicide?
Chempa contains pyrazosulfuron-ethyl 10% WP, an acetolactate synthase (ALS) inhibitor sulfonylurea herbicide.
When should Chempa be applied in paddy?
Apply 3 to 7 days after transplanting (or direct seeding) when the field has shallow standing water and weeds are at the 1 to 2 leaf stage.
Can Chempa be broadcast with sand?
Yes, it can be mixed with clean dry sand or fertilizer and broadcast uniformly across fields with standing water.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
More General Agriculture & Tools guides
Ask Sakhi AI in your language, check live mandi prices or plan a loan with KisanPe tools.