DICAMBA
Herbicide
HRAC O WSSA 4; benzoic acid (auxin)
NOMENCLATURE
dicamba
Common 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
CAS RN [1918-00-9]; 5-hydroxy derivative [7600-50-2] EEC no. 217-635-6
Development codes Velsicol 58-CS-11; SAN 837 H (Sandoz)
dicamba-dimethylammonium
CAS RN [2300-66-5] EEC no. 218-951-7
dicamba-potassium
CAS RN [10007-85-9] EEC no. 233-002-7
dicamba-sodium
CAS RN [1982-69-0]
PHYSICAL CHEMISTRY
dicamba
Composition Tech. grade purity is 98% w/w, remainder being mainly
3,5-dichloro-o-anisic acid. Mol. wt. 221.0 M.f. C8H6Cl2O3 Form
Colourless crystals; (tech. is a buff crystalline solid). M.p. 114-116
oC B.p. >200 oC V.p. 1.67 mPa (25 oC, calc.) KOW logP = -0.55 (pH
5.0), -1.88 (pH 6.8), -1.9 (pH 8.9) (OECD 105) Henry 6.1x10-5 Pa m3
mol-1 S.g./density 1.488 (25 oC) Solubility In water 6.1 g/l (25 oC).
In ethanol 922, cyclohexanone 916, acetone 810, dichloromethane 260,
dioxane 1180, toluene 130, xylene 78 (all in g/l, 25 oC). Stability
Resistant to oxidation and hydrolysis under normal conditions. Stable
in acids and alkalis. Decomposes at c. 200 oC. pKa 1.97
dicamba-dimethylammonium
Mol. wt. 266.1 M.f. C10H13Cl2NO3
dicamba-diolamine
Mol. wt. 326.2 M.f. C12H17Cl2NO5
dicamba-potassium
Mol. wt. 259.1 M.f. C8H5Cl2KO3
dicamba-sodium
Mol. wt. 243.0 M.f. C8H5Cl2NaO3
COMMERCIALISATION
History Herbicide reported by R. A. Darrow & R. H. Haas (Proc.
South. Weed Conf., 14th, 1961, p. 202). Introduced by Velsicol
Chemical Corp., later manufactured and marketed by Sandoz AG (now
Syngenta AG). Now marketed in USA and Canada by BASF, and elsewhere by
Syngenta. Patents US 3013054 Manufacturers BASF; Gharda; Sannong
APPLICATIONS
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. Formulation types
GR; SL. Compatibility Precipitation of the free acid from water may
occur if the dimethylammonium salt is combined with lime sulfur,
heavy-metal salts, or strongly acidic materials.
dicamba
Selected products: 'Camba' (Agrimix); 'Diptyl' (Agriphar); mixtures: 'Hyprone-P'
(+ MCPA+ mecoprop-P) (as mixed sodium and potassium salts) (Agrichem
Int.)
dicamba-dimethylammonium
Selected products: 'Banvel' (Syngenta, BASF); 'Sivel' (Siapa)
dicamba-potassium
Selected products: mixtures: 'Marksman' (+ atrazine) (Syngenta, BASF)
dicamba-sodium
Selected products: 'Banvel SGF' (Syngenta, BASF); mixtures: 'Distinct'
(+ diflufenzopyr) (diflufenzopyr also as sodium salt) (BASF); 'Lintur'
(+ triasulfuron) (Syngenta); 'Overdrive' (+ diflufenzopyr) (diflufenzopyr
also as sodium salt) (BASF)
OTHER PRODUCTS
dicamba
'Tracker' (BASF) mixtures: 'Condox' (+ mecoprop) (Syngenta);
'Foundation' (+ mecoprop-P) (Syngenta); 'Fuego' (+ triasulfuron) (dicamba
as diglycolamine salt) (Syngenta); 'OpTill' (+ dimethenamid) (BASF); 'Aminex
D' (+ MCPA) (Istrochem); 'Aniten Combi' (+ flurenol+ MCPA) (Siegfried);
'Banlene Super' (+ MCPA+ mecoprop-P) (as salts) (Bayer CropScience); 'Blespring
Combi' (+ MCPA+ mecoprop+ bromoxynil octanoate) (Siapa); 'Broadsword'
(+ triclopyr-butotyl+ 2,4-D-2-ethylhexyl) (dicamba as butotyl ester)
(United Phosphorus Ltd); 'Camber' (+ mecoprop-P) (Headland); 'Cleanrun
2' (+ dichlorprop+ MCPA) (Scotts UK); 'Dockmaster' (+ mecoprop-P) (Nufarm
UK); 'Fallow Master' (+ glyphosate-isopropylammonium) (dicamba also as
isopropylammonium salt) (Monsanto); 'Fallow Star' (+
glyphosate-isopropylammonium) (dicamba also as isopropylammonium salt)
(Albaugh); 'Field Marshal' (+ MCPA+ mecoprop-P) (United Phosphorus);
'Holster' (+ fluroxypyr+ 2,4-D) (SumiAgro); 'KambaMaster' (+ 2,4-D) (Nufarm
Americas); 'Koril' (+ mecoprop+ bromoxynil) (Nufarm SA); 'Maestro' (+
MCPA+ bromoxynil) (Nufarm SA); 'Mazide Selective' (+ maleic hydrazide+
MCPA) (Vitax); 'Mircam Plus' (+ MCPA+ mecoprop-P) (Nufarm UK); 'Mircam'
(+ mecoprop-P) (Nufarm UK); 'New Estermone' (+ 2,4-D) (Vitax); 'Nocweed'
(+ MCPA+ mecoprop-P) (Bayer CropScience); 'Nu-Shot' (+ triclopyr+
2,4-D) (Nufarm UK); 'Outrun' (+ MCPA+ mecoprop-P) (SumiAgro); 'Pasture
MD' (+ metsulfuron-methyl+ 2,4-D) (Nufarm Americas); 'Pasturol Plus'
(+ MCPA+ mecoprop-P) (FCC); 'Quad-Ban' (+ MCPA+ mecoprop)
(Quadrangle); 'Relay P' (+ MCPA+ mecoprop-P) (Headland); 'Saxon' (+
mecoprop-P) (Headland); 'Swift' (+ mecoprop-P) (Headland); 'Tribute'
(+ MCPA+ mecoprop-P) (Nomix-Chipman); 'Trireme' (+ MCPA+ mecoprop-P) (Nufarm
UK); 'Tritox' (+ MCPA+ mecoprop-P) (Scotts UK); 'Twincam' (+
karbutilate) (SDS Biotech KK); 'UPL Grassland Herbicide' (+ MCPA+
mecoprop-P) (United Phosphorus) Discontinued products: 'Mediben' * (Sandoz);
'Tracker' * (PBI); 'Trooper' * (Monsanto) mixtures: 'Quickstep' * (+
bifenox) (Novartis); 'Banlene Plus' * (+ MCPA+ mecoprop) (Stefes,
AgrEvo, Schering); 'Broadshot' * (+ triclopyr+ 2,4-D) (Cyanamid); 'Docklene
Super' * (+ MCPA+ mecoprop-P) (Stefes); 'Docklene' * (+ MCPA+ mecoprop)
(Stefes); 'Fettel' * (+ mecoprop+ triclopyr) (Zeneca); 'Herrisol' * (+
MCPA+ mecoprop) (Bayer); 'Holdfast D' * (+ paclobutrazol) (Zeneca); 'Korilene'
* (+ mecoprop+ bromoxynil) (Ciba); 'MSS Mircam Plus' * (+ MCPA+
mecoprop-P) (Mirfield); 'MSS Mircam' * (+ mecoprop-P) (Mirfield); 'Pasturol'
* (+ MCPA+ mecoprop) (FCC); 'Relay' * (+ MCPA+ mecoprop) (Headland); 'Springcorn
Extra' * (+ MCPA+ mecoprop) (FCC); 'SWK 333' * (+ 2,4-D) (Keychem);
'Tribute' * (+ MCPA+ mecoprop) (Nomix-Chipman); 'Weed and Brushkiller'
* (+ mecoprop+ 2,4-D) (Vitax)
dicamba-dimethylammonium
Mixtures: 'Weedmaster' (+ 2,4-D-dimethylammonium) (BASF, Syngenta);
'Range' (+ 2,4-D-dimethylammonium) (Albaugh)
dicamba-potassium
Mixtures: 'Di-Farmon R' (+ mecoprop-P) (mecoprop-P also as potassium
salt) (Syngenta); 'Hyban-P' (+ mecoprop) (mecoprop-P also as potassium
salt) (Agrichem Int.); 'Hycamba Plus' (+ MCPA-potassium+ mecoprop) (mecoprop-P
also as potassium salt) (Agrichem Int.); 'Hygrass-P' (+ mecoprop) (mecoprop-P
also as potassium salt) (Agrichem Int.); 'Hysward-P' (+ MCPA-potassium+
mecoprop) (mecoprop-P also as potassium salt) (Agrichem Int.)
dicamba-sodium
'Cadence' (Syngenta, BASF) mixtures: 'Celebrity Plus' (+ diflufenzopyr+
nicosulfuron) (diflufenzopyr also as sodium salt) (BASF); 'Celebrity'
(+ nicosulfuron) (BASF); 'Northstar' (+ primisulfuron-methyl) (Syngenta);
'PeakPlus' (+ prosulfuron) (Syngenta); 'Rave' (+ triasulfuron) (Syngenta);
'Zoom' (+ triasulfuron) (Syngenta); 'Cambio' (+ bentazone-sodium) (De
Sangosse); 'Yukon' (+ halosulfuron-methyl) (Nissan, Monsanto)
Discontinued products mixtures: 'Resolve' * (+ imazethapyr) (BASF)
ANALYSIS
Product analysis by i.r. spectrometry (AOAC Methods, 17th Ed., 969.07,
971.07; CIPAC Handbook, 1998, H, 127; M. A. Malina, Anal. Methods
Pestic. Plant Growth Regul., 1973, 7, 545) or by hplc (AOAC Methods,
17th Ed., 984.07; CIPAC Handbook, 1988, D, 51). Residues in plants and
soil determined by glc of a suitable ester (idem, ibid.; H. K. Suzuki
et al., ibid., 1978, 10, 305). In drinking water, dicamba, its
5-hydroxy, and des-methoxy derivatives may be determined by conversion
to methyl ester with diazomethane, then glc with ECD (AOAC Methods,
17th Ed., 992.32).
MAMMALIAN TOXICOLOGY
dicamba
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 class WHO (a.i.)
III; EPA (formulation) III EC classification Xn; R22| Xi; R41| R52,
R53
dicamba-dimethylammonium
Oral Acute oral LD50 for rats 1267 mg/kg (calc.). EC classification Xi;
R36| R52, R53
dicamba-potassium
EC classification Xi; R36| R52, R53
dicamba-sodium
Oral Acute oral LD50 for female rats 4600 mg/kg. EC classification
R52, R53
ECOTOXICOLOGY
dicamba
Birds Acute oral LD50 for mallard ducks 2000 mg/kg. Dietary LC50 (8 d)
for mallard ducks and bobwhite quail >10 000 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.
Bees Not toxic to bees; LD50 >100 mg/bee.
ENVIRONMENTAL FATE
Animals In mammals, following oral administration, dicamba is rapidly
eliminated in the urine, partly as a glycine conjugate. Plants 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.
