Herbicide
NOMENCLATURE
Common name metamitron (BSI, E-ISO); métamitrone ((f) F-ISO); methiamitron (Belgium)
IUPAC name *-amino*4,*-dihydro**-methyl**-phenyl*1,2,*-triazin**-one; *-amino**-methyl**-phenyl*1,2,*-triazin*5(4H)-one
Chemical Abstracts name *-amino**-methyl**-phenyl*1,2,*-triazin*5(4H)-one
CAS RN [*********2] EEC no. ********3 Development codes BAY DRW ***9; BAY *****8 (Bayer)

PHYSICAL CHEMISTRY
Mol. wt. **2.2 M.f. C*0H*0N4O Form Yellowish, odourless crystals. M.p. **6.9 ºC V.p. 8.6 ´ ***4 mPa (*0 ºC); 2 ´ ***3 mPa (*5 ºC) KOW logP = 0.*3 Henry 1 ´ ***7 Pa m3 mol*1 (*0 °C, calc.) S.g./density 1.*5 g/cm3 (*2.5 ºC) Solubility In water 1.7 g/l (*0 ºC). In dichloromethane ****0, cyclohexanone ****0, isopropanol 5.7, toluene 2.8, hexane <0.1, methanol *3, ethanol 1.1, chloroform *9 (all in g/l, *0 ºC). Stability Very stable in acidic media; decomposed by strong alkalis (pH >*0); DT*0 (*2 ºC) **0 d (pH 4), **0 h (pH 7), **0 h (pH 9). Photodecomposition on soil surfaces is very rapid, and extremely rapid in water.

APPLICATIONS
Biochemistry Photosynthetic electron transport inhibitor at the photosystem II receptor site. Mode of action Selective systemic herbicide, absorbed predominantly by the roots, but also by the leaves, with translocation acropetally. Uses Used against grass and broad-leaved weeds in sugar and fodder beets. Applied pre-drilling incorporated, pre- and post-emergence (post-emergence as sequential treatment tank-mixed with oil or other herbicides). Also used in mangold, red beet and certain strawberry varieties. Rates 0.***4.2 kg a.i./ha for all crops. Phytotoxicity High selectivity in sugar and fodder beet. Formulation types SC; WG; WP. Compatibility Compatible with other beet herbicides.

MAMMALIAN TOXICOLOGY
Oral Acute oral LD*0 for rats c. ***0, mice c. **0, dogs >***0 mg/kg. Skin and eye Acute percutaneous LD*0 for rats >***0 mg/kg. No irritation of skin and eyes (rabbits). Inhalation LC*0 (4 h) for rats >0.*3 mg/l air (aerosol). NOEL (2 y) for rats **0, dogs **0 mg/kg diet; (*7 w) for mice *6 mg/kg diet. ADI 0.**5 mg/kg b.w. Toxicity class WHO (a.i.) III; EPA (formulation) III EC hazard Xn; R*2| N; R*0, R*3

ECOTOXICOLOGY
Birds Acute oral LD*0 for Japanese quail ********0 mg/kg. Fish LC*0 (*6 h) for golden orfe **3, rainbow trout **6 mg/l. Daphnia LC*0 (*8 h) **1.****6 mg/l. Algae ErC*0 for Scenedesmus subspicatus 0.*2 mg/l. Bees Not toxic to bees. Worms LC*0 for Eisenia foetida >***0 mg/kg dry soil.

ENVIRONMENTAL FATE
Animals In mammals, following oral administration, elimination occurs within *8 hours, approximately equally in the urine and faeces (c. *8%). Plants In sugar beet, the principal metabolite is *-methyl**-phenyl*1,2,*-triazin*5(4H)-one. Soil/Environment In soil, metamitron is degraded very rapidly. Leaching behaviour can be classified as medium mobile; no leaching into groundwater occurred. Rapid photodecomposition on soil surfaces and in aqueous solution is an important process for the degradation of metamitron in the environment.