Herbicide

HRAC  C1 WSSA  5; 1,3,5-triazine

NOMENCLATURE

Common name ametryn (BSI (since 1984), E-ISO, ANSI, WSSA, JMAF); ametryne (BSI (before 1984), (f) F-ISO)

IUPAC name N2-ethyl-N4-isopropyl-6-methylthio-1,3,5-triazine-2,4-diamine 

Chemical Abstracts name N-ethyl-N'-(1-methylethyl)-6-(methylthio)-1,3,5-triazine-2,4-diamine 

CAS RN [834-12-8]  EEC no. 212-634-7  Development codes G 34 162 (Geigy) 

PHYSICAL CHEMISTRY

Composition 96% pure.  Mol. wt. 227.3  M.f. C9H17N5S  Form White powder.  M.p. 86.3-87.0 ºC  B.p. 337 °C/98.6 kPa  V.p. 0.365 mPa (25 ºC) (OECD 104)  KOW logP = 2.63 (25 ºC)  Henry 4.1 ´ 10-4 Pa m3 mol-1 (calc.)  S.g./density 1.18 (22 ºC)  Solubility In water 200 mg/l (20 ºC). In acetone 610, methanol 510, toluene 470, n-octanol 220, hexane 12 (all in g/l, 25 ºC).  Stability Stable in neutral, weakly acidic, and weakly alkaline media. Hydrolysed by strong acids (pH 1) and alkalis (pH 13) to the herbicidally-inactive 6-hydroxy derivative. Slowly decomposed by u.v. light.  pKa 4.1, weak base 

COMMERCIALISATION

History Herbicide reported by H. Gysin & E. Knüsli (Adv. Pest Control Res., 1960, 3, 289). Introduced by J. R. Geigy S.A. (now Syngenta AG).  Patents GB 814948; CH 337019  Manufacturers Crystal; Hegang Heyou; Makhteshim-Agan; Oxon; Syngenta

APPLICATIONS

Biochemistry Photosynthetic electron transport inhibitor at the photosystem II receptor site.  Mode of action Selective systemic herbicide, absorbed by the leaves and roots, with translocation acropetally in the xylem, and accumulation in the apical meristems.  Uses Pre- and post-emergence control of most annual grasses and broad-leaved weeds in pineapples, sugar cane, bananas, citrus fruit, maize, cassava, coffee, tea, sisal, cocoa, oil palms, and on non-crop land. Application rates are in the range 2-4 kg/ha, except when used as a directed spray on maize. Also used as a potato haulm desiccant.  Phytotoxicity Some sugar cane varieties show temporary chlorosis and scorching of lower leaves.  Formulation types EC; FW; SC; WG; WP.  Selected tradenames: 'Evik' (USA) (Syngenta); 'Gesapax' (Syngenta); 'Ameflow' (Inquiport); 'Amesip' (Sipcam); 'Ametrex' (Makhteshim-Agan); 'Mebatryne' (Aventis); mixtures: 'Krismat' (+ trifloxysulfuron) (trifloxysulfuron as sodium salt) (Bayer)

OTHER TRADENAMES

'Crisatrina' (Crystal) mixtures: 'Codal' (+ prometryn) (Syngenta); 'Amigan' (+ terbutryn) (Makhteshim-Agan); 'Atramet Combi' (+ atrazine) (Makhteshim-Agan)

ANALYSIS

Product analysis by glc with FID (CIPAC Handbook, 1980, 1A, 1102; FAO Specification CP/61; AOAC Methods, 1995, 971.08). Residues determined by glc (K. Ramsteiner et al., J. Assoc. Off. Anal. Chem., 1974, 57, 192; E. Knüsli, Anal. Methods Pestic. Plant Growth Regul. Food Addit., 1964, 4, 13; B. G. Tweedy & R. A. Kahrs, Anal. Methods Pestic. Plant Growth Regul., 1978, 10, 493). In drinking water, by gc with FID; AOAC Methods, 1995, 991.07. 

MAMMALIAN TOXICOLOGY

Reviews J. Pest. Sci., 18(4), 1993 (in Japanese).  Oral Acute oral LD50 for rats 1160 mg tech./kg.  Skin and eye Acute percutaneous LD50 for rabbits >2020, rats >3100 mg/kg. Not a skin or eye irritant (rabbits). Not a skin sensitiser (guinea pigs).  Inhalation LC50 (4 h) for rats >5170 mg/m3 air.  NOEL (2 y) for rats 50, for mice 10 ppm; (1 y) for dogs 200 ppm.  ADI 0.015 mg/kg daily.  Toxicity class WHO (a.i.) III; EPA (formulation) III  EC hazard Xn; R22| N; R50, R53 

ECOTOXICOLOGY

Birds LC50 (5 d) for bobwhite quail and mallard ducks >5620 ppm.  Fish LC50 (96 h) for rainbow trout 5, bluegill sunfish 19, channel catfish 25 mg/l.  Daphnia LC50 (96 h) 28 mg/l.  Algae EC50 (7 d) for Selenastrum capricornutum 0.0036 mg/l.  Other aquatic spp. LC50 (96 h) for mysid shrimp (Mysidopsis bahia) 2.3 mg/l.  Bees Low toxicity to bees; LD50 (oral) >100 mg/bee.  Worms LC50 (14 d) for earthworms 166 mg/kg soil. 

ENVIRONMENTAL FATE