IDENTIFICATION
Common name:Dicamba
Other name: dicamba (BSI, E-ISO, (m) F-ISO, ANSI, WSSA); dianat* (former exception, USSR); MDBA (JMAF)
Iupac name: 3,6-dichloro-o-anisic acid
Chemical abstracts name: 3,6-dichloro-2-methoxybenzoic acid
Type: Herbicide
CAS RN: [1918-00-9]; 5-hydroxy derivative [7600-50-2]
M.F.: C8H6Cl2O3
Mol Wt: 221.0
PHYSICAL CHEMISTRY
Form (appearance): /Colourless crystals; (tech. is a buff crystalline solid. ).
Composition: Tech. grade purity is 85% w/w, remainder being mainly 3,5-dichloro-O-anisic acid.
M.P.: 114-116℃
B.P.: >200℃
V.P.: 1.67 mPa (25℃, calc.)
S.G.: 1.488 (25℃)
Solubility.: In water 6.1 g/l (25℃). In ethanol 922, cyclohexanone 916, acetone 810, dichloromethane 260, dioxane 1180, toluene 130, xylene 78 (all in g/l, 25℃).
Stability: Resistant to oxidation and hydrolysis under normal conditions. Stable in acids and alkalis. Decomposes at c. 200℃.
Henry: 6.1 × 10-5 Pa m3 mol-1
KowlogP: -0.55 (pH 5.0), -1.88 (pH 6.8), -1.9 (pH 8.9) (OECD 105)
Pka:1.97
APPLICATION
Formulation types: GR; SL.
Biochemistry: Synthetic auxin (acting like indolylacetic acid).
Mode of action: Selective systemic herbicide, absorbed by the leaves and roots, with ready translocation throughout the plant via both the symplastic and apoplastic systems. Acts as an auxin-like growth regulator.
Uses: Control of annual and perennial broad-leaved weeds and brush species in cereals, maize, sorghum, sugar cane, asparagus, perennial seed grasses, turf, pastures, rangeland, and non-crop land. Used in combinations with many other herbicides. Dosage varies with specific use and ranges from 0.1 to 0.4 kg/ha for crop use, higher rates in pasture.
Phytotoxicity: Most legumes are sensitive.
MAMMALIAN TOXICOLOGY
Oral: Acute oral LD50 for rats 1707 mg/kg.
Skin and eye: Acute percutaneous LD50 for rabbits >2000 mg/kg. Extremely irritating and corrosive to eyes; moderately irritating to skin (rabbits).
Inhalation: LC50 (4 h) for rats >9.6 mg/l.
Noel: (2 y) for rats 110 mg/kg b.w. daily; (1 y) for dogs 52 mg/kg b.w. daily. Developmental NOEL for rabbits 30 mg/kg b.w. daily, rats 160 mg/kg b.w. daily. Reproduction NOEL for rats 50 mg/kg b.w. daily. Not mutagenic.
Toxicity: WHO (a.i.) III (Table 5); EPA (formulation) III
EC hazard: Xn; R22|Xi; R41| R52, R53
ECOTOXICOLOGY
Birds: Acute oral LD50 for mallard ducks 2000 mg/kg. Dietary LC50 (8 d) for mallard ducks and bobwhite quail >10000 mg/kg diet.
Fish: LC50 (96 h) for rainbow trout and bluegill sunfish 135 mg/l.
Daphnia: LC50 (48 h) 110 mg/l.
Algae: LC50 41 to >250 mg/l (depending on species).
Worms: Bee: Not toxic to bees; LD50 >100μg/bee.
ENVIRONMENTAL FATE
Plant: The degradation rate in plants varies greatly with species. In wheat, the major metabolite is 5-hydroxy-2-methoxy-3,6-dichlorobenzoic acid, whilst- 3,6-dichlorosalicylic acid is also a metabolite. Soil/Environment In soil, microbial degradation occurs, the principal metabolite being 3,6-dichlorosalicylic acid. Under conditions amenable to rapid metabolism, DT50 <14 d. Koc 2.
Animals: In mammals, following oral administration, dicamba is rapidly eliminated in the urine, partly as a glycine conjugate. |
