Herbicide

HRAC  I WSSA  18; carbamate (DHP)

NOMENCLATURE

asulam

Common name asulam (BSI, E-ISO, ANSI, WSSA, JMAF); asulame ((m) F-ISO); no name (Germany)

IUPAC name methyl sulfanilylcarbamate 

Chemical Abstracts name methyl [(4-aminophenyl)sulfonyl]carbamate 

CAS RN [3337-71-1]  Development codes M&B 9057 (May & Baker) 

asulam-sodium

Common name asulam-sodium

CAS RN [2302-17-2] 

PHYSICAL CHEMISTRY

asulam

Mol. wt. 230.2  M.f. C8H10N2O4S  Form Colourless crystals.  M.p. 142-144 ºC (decomp.)  V.p. <1 mPa (20 ºC)  Solubility In water 5 g/l (20-25 ºC). In dimethylformamide >800, acetone 340, methanol 280, methyl ethyl ketone 280, ethanol 120, hydrocarbons and chlorinated hydrocarbons <20 (all in g/l, 20-25 ºC). Other salts: in water, sodium >600, potassium >400, ammonium >400, calcium >200, magnesium >400 (all in g/l, 20-25 ºC).  Stability Stable in boiling water ³6 h. Stable >4 y (pH 8.5, room temperature).  pKa 4.82, forming water-soluble salts 

asulam-sodium

Mol. wt. 252.2  M.f. C8H9N2NaO4S  Solubility In water >600 g/l (20-25 ºC) 

COMMERCIALISATION

History Herbicide reported by H. J. Cottrell & B. J. Heywood (Nature (London), 1965, 207, 655). Introduced by May & Baker Ltd (now Aventis CropScience).  Patents GB 1040541  Manufacturers Aventis; High Kite; Sanachem; Shionogi

APPLICATIONS

Biochemistry Inhibition of dihydropteroate synthase.  Mode of action Selective systemic herbicide, absorbed by the leaves, shoots, and roots, with translocation in both the symplastic and apoplastic systems to other parts of the plant. Causes a slow chlorosis in susceptible plants.  Uses Control of annual and perennial grasses and broad-leaved weeds in spinach, oilseed poppies, alfalfa, some ornamentals, sugar cane, bananas, coffee, tea, cocoa, coconuts, rubber, etc.; wild oats in flax; docks (Rumex spp.) in grassland, fruit trees and bushes, and on non-crop land; and bracken (Pteridium aquilinum) in grassland, non-crop land, and forestry. Application rates from 1-10 kg/ha, depending on crop.  Formulation types SL. 

asulam

Selected tradenames: 'Asulox 40' (Aventis); 'Asilan' (Shionogi); 'Sanulam' (Sanachem)

OTHER TRADENAMES

asulam

'Fougerox' (Aventis)

asulam-sodium

'Asulox' (Aventis)

ANALYSIS

Product analysis by hplc (A. Guardigli et al., Anal. Methods Pestic. Plant Growth Regul., 1984, 13, 197) or by hydrolysis with colorimetry of a derivative (C. H. Brockelsby & D. F. Muggleton, ibid., 1973, 7, 497). Residues determined by the latter method (idem, ibid.) or by hplc of a derivative (A. Guardigli et al., loc. cit.). 

MAMMALIAN TOXICOLOGY

Reviews M. A. Gallo et al., Effect of asulam in wildlife species, residues and toxicity in bobwhite quail after prolonged exposure, Bull. Environ. Contam. Toxicol., 1975, 13(2), 200-205. B. Ingham & M. A. Gallo, Effect of asulam in wildlife species - acute toxicity to birds and fish, Proc. Northeast Weed Control Conf., 1975, (1), 194-199.  Oral Acute oral LD50 for rats, mice, rabbits, and dogs >4000 mg/kg.  Skin and eye Acute percutaneous LD50 for rats >1200 mg/kg.  Inhalation LC50 (6 h) for rats >1.8 mg/l air.  NOEL In 90 d feeding trials, rats receiving 400 mg/kg diet showed no significant ill-effects. No effect observed when fed to cows at 800 ppm over 8 w, or to sheep at 50 mg/kg over 10 d. Non-teratogenic.  Toxicity class WHO (a.i.) III (Table 5); EPA (formulation) IV 

ECOTOXICOLOGY

asulam

Birds Acute oral LD50 for mallard ducks, pheasants, and pigeons >4000 mg/kg.  Fish LC50 (96 h) for rainbow trout, channel catfish, and goldfish >5000, bluegill sunfish >3000, harlequin fish >1700 mg/l.  Bees Not toxic to bees at <2% w/v by direct contact or ingestion. 

asulam-sodium

Birds Acute oral LD50 for chickens, pigeons, quail >2000 mg/kg. 

ENVIRONMENTAL FATE