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Chemical Identification
Common Name
Molecular Formula
Molecular Structure
The biochemical mode of action of fentrazamide has still not been identified. However, from morphological studies it is believed to be similar to that of oxyacetamides and chloroacetamides. By comparison with published data on chloroacetanilides, a primary target site in fatty acid modification is suggested. Fentrazamide inhibits cell division and cell growth, particularly in the meristematic tissue in the root and shoot tips - the roots and shoots of the weeds stop growing and become distorted. Fentrazamide can be classified in group K3 (inhibition of cell division) of the Herbicide Resistance Action Committee (HRAC) classification system.

Fentrazamide can be applied from pre-emergence to early post-emergence of weeds in transplanted and direct-seeded rice. For transplanted rice, the selectivity arises because the growth point of Echinochloa crus-galli comes into contact with fentrazamide in the treatment layer on the soil surface, whilst that of the transplanted rice does not as it is under the treatment layer. The herbicide has residual activity lasting throughout the growing season.

In the field, fentrazamide applied at zero DAT at a rate of 150-200 g ai/ha was found to control Echinochloa oryzicola, Cyperus difformis, Monochoria vaginalis and Eleocharis acicularis. Similar control was found at the 2-leaf stage of Echinochloa using an application rate of 200 - 300 g/ha. Applications at the 3 leaf stage of Echinochloaat a rate of 200 - 300 g/ha controlled Cyperus difformis and Eleocharis acicularis. There is no acceptable control of Cyperus serotinus, Scirpus juncoides,Sagittaria pygmoides and broadleaf weeds.

In Thailand, fentrazamide is used in early post-emergence applications to control Cyperus spp and Fimbristylis miliacea. Treatments are made 7 to 12 days after sowing. In Malaysia, Vietnam and the Philippines, Lecspro has been successfully introduced for control of a broad range of rice weeds including Echinochloa crus-galli, Fimbristylis spp, and broadleaf weeds such as Ludwigia spp.

200-300 g ai/ha (Japan, Korea)


135 g ai/ha (South-East Asia)


Disease Spectrum
Weed Spectrum
Pest Spectrum

Wettable powder 
Premix Parters: fenoxaprop-P-ethyl; fomesafen;

Physical Properties
Molecular weight:349.8; Physical form:Colourless crystals. Density:1.30 (20 °C); Melting point:79 °C; Vapour pressure:5 × 10-5 mPa (20 °C); Henry constant:7 × 10-6 Pa m3 mol-1 ( calc.); Partition coefficient(n-octanol and water):logP = 3.60 (20 °C); Solubility:In water 2.3 mg/l (20 °C). In n-heptane 2.1, isopropanol 32, dichloromethane and xylene >250 (all in g/l, 20 °C).; Stability: DT50 ( pH 5) >300 d, ( pH 7) >500 d, ( pH 9) c. 70 d (all 25 °C). In pure water, photolysis DT50 c. 20 d; in natural water, c.;
Oral:Acute oral LD50 for rats >5000 mg/ kg. Percutaneous:Acute percutaneous LD50 for rats >5000 mg/kg. Not an eye or skin irritant (rabbits); not a skin sensitiser (guinea pigs). Inhalation: LC50 for rats >5000 mg/m3. ADI:( JMPR) 0.0005 mg/ kg b.w. [1991].
Environmental Profile
Algae:EpC50 (72 h) for green algae 6.04 mg/l; no long-term impact on algae, quick recovery.Bees: LD50 (topical) for honeybees >150 mg/bee.Birds:Acute oral LD50 (14 d) for Japanese quail and bobwhite quail >2000 mg/ kg.Daphnia: LC50 (24 h) >10 mg/l.Fish: LC50 (96 h) for carp 3.2, rainbow trout 3.4 mg/l.Worms: LC50 (14 d) for Eisenia foetida >1000 mg/ kg dry substrate.Other aquatic spp.: LC50 (96 h) for freshwater shrimps 6.5, Corbicula mussels >100 mg/l.Other beneficial spp.: NOEC for silkworms 100 ppm. 

Environmental fate: 
Animals:The main pathway of biotransformation proceeded via hydrolytic cleavage of the parent compound.Soil:Under paddy soil conditions, fentrazamide was rapidly eliminated from the water phase and thoroughly degraded and mineralised in the submerged soils. In field and laboratory trials under paddy conditions, the calculated half-lives were in the range of a fPlant:Metabolism was investigated in rice plants under paddy conditions; no parent compound was detected in any plant fraction.
Transport Information
Hazard Class:O (Obsolete as pesticide, not classified)

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