pyrethroid

NOMENCLATURE

Common name deltamethrin (BSI, draft E-ISO); deltaméthrine ((f) draft F-ISO)
IUPAC name (S)-?-cyano-3-phenoxybenzyl (1R,3R)-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate
Roth: (S)-?-cyano-3-phenoxybenzyl (1R)-cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate
Chemical Abstracts name [1R-[1?(S*),3?]]-cyano(3-phenoxyphenyl)methyl 3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropanecarboxylate
Other names decamethrin* (rejected common name proposal) CAS RN [52918-63-5]; [52820-00-5] ((RS)- (1R)-cis- isomer pair) EEC no. 258-256-6

PHYSICAL CHEMISTRY

Composition Tech. produced industrially by Aventis contains ?98% deltamethrin (i.e. the single isomer). Mol. wt. 505.2 M.f. C22H19Br2NO3 Form Colourless crystals. M.p. 100-102 oC V.p. 1.24 ? 10-5 mPa (25 °C, gas saturation method) KOW logP = 4.6 (25 oC) Henry 3.13 ? 10-2 Pa m3 mol-1 (calc.) S.g./density Bulk density 0.55 g/cm3 (25 oC) Solubility In water <0.2 ?g/l (25 oC). In dioxane 900, cyclohexanone 750, dichloromethane 700, acetone 500, benzene 450, dimethyl sulfoxide 450, xylene 250, ethanol 15, isopropanol 6 (all in g/l, 20 oC). Stability Extremely stable on exposure to air. Stable ?190 oC. Under u.v. irradiation and in sunlight, a cis-trans isomerisation, splitting of the ester bond, and loss of bromine occur. More stable in acidic than in alkaline media; DT50 2.5 d (pH 9, 25 oC). Specific rotation [?]D +61?(40 g/l benzene)

COMMERCIALISATION

History This single isomer, first described by M. Elliott et al. (Nature (London), 1974, 248, 710), and reviewed in Deltamethrin Monograph and by J. Tessier (Chem. Ind., 1984, p. 199) was introduced by Roussel Uclaf (now Aventis). Patents GB 1413491 to NRDC

APPLICATIONS

Biochemistry Like all pyrethroids, prevents the sodium channels from functioning, so that no transmission of nerve impulses can take place. Mode of action Non-systemic insecticide with contact and stomach action. Fast-acting. Uses A potent insecticide, effective by contact and ingestion against a wide range of pests. Crop protection uses include: Coleoptera (2.5-7.5 g/ha), Heteroptera (5.0-7.5 g/ha), Homoptera (6.2-12.5 g/ha), Lepidoptera (5.0-21 g/ha) and Thysanoptera (5-10 g/ha) in cereals, citrus, cotton, grapes, maize, oilseed rape, soya beans, top fruit and vegetables. It controls Acrididae (5.0-12.5 g/ha), and is recommended against locusts. Soil surface sprays (2.5-5.0 g/ha) control Noctuidae. It is used against indoor crawling and flying insects (12.5 mg/m2) and pests of stored grain (0.25-0.5 g/t) and timber (Blattodea, Culicidae, Muscidae). Dip or spray (12.5-75 mg/l), and pour-on (0.75 mg/kg b.w.) applications give good control of Muscidae, Tabanidae, Ixodidae and other Acari on cattle, sheep and pigs, etc. Formulation types DP; EC; EG; EW; GR; HN; PO; SC; SL; TB; UL; WG; WP. Selected tradenames: 'Decis' (crop protection uses) (Aventis); 'Kordon' (environmental health uses) (Aventis); 'K-Othrine' (environmental health uses) (Aventis); 'Butox' (veterinary uses) (Intervet); 'Delta' (Nagarjuna Agrichem); 'Deltamix' (Agrimix); 'Sadethrin' (Sanonda)

OTHER TRADENAMES

'Bitam' (crop protection uses) (Aventis); 'Cislin' (environmental health uses) (Aventis); 'Decistab' (Aventis); 'Delsekte' (environmental health uses) (Aventis); 'K-Otek' (environmental health uses) (Aventis); 'Pearl Micro' (Aventis); 'Tess' (crop protection uses) (Aventis); 'Delete' (Vapco); 'Deltarin' (Vapco); 'Deltarocca' (Rocca); 'Flayethrin' (Agrochem); 'Keshet' (Makhteshim-Agan); 'Terminator' (Vapco); 'Thripstick' (Aquaspersions); 'Thrust' (Crop Health) mixtures: 'Adage' (+ pirimicarb) (Aventis); 'Akaridecis' (+ propargite) (Aventis); 'Best' (+ pirimicarb) (Aventis); 'Crackdown' (+ bioallethrin S-cyclopentenyl isomer) (environmental health uses) (Aventis); 'Dadeci' (+ buprofezin) (Aventis); 'Decis D' (+ dimethoate) (Aventis); 'Decisdan' (+ endosulfan) (Aventis); 'Decisprime' (+ chlorpyrifos-methyl) (Aventis); 'Decisquick' (+ heptenophos) (Aventis); 'Deltaphos' (+ triazophos) (Aventis); 'Evidence' (+ pirimicarb) (Aventis); 'K-obiol' (+ piperonyl butoxide) (Aventis); 'Patriot' (+ pirimicarb) (Aventis); 'Mieling' (+ phoxim) (Zhong-Xi) Discontinued names: 'Landgold Deltaland' * (Landgold); 'Sputop' * (Coopers)

ANALYSIS

Product analysis by lc with u.v. detection (AOAC Methods, 1995, 991.03, 7.5.05) or by hplc (CIPAC Handbook, 1988, D, 57; M. Vaysse et al., Anal. Methods Pestic. Plant Growth Regul., 1984, 13, 53). Residues determined by glc with ECD (Man. Pestic. Residue Anal., 1987, I, 6, S19; Anal. Methods Residues Pestic., 1988, Part I, M11; A. Ambrus et al., J. Assoc. Off. Anal. Chem., 1981, 64, 733; P. G. Baker & P. Bottomley, Analyst (London), 1982, 107, 206; P. Bottomley & P. G. Baker, ibid., 1984, 109, 85).

MAMMALIAN TOXICOLOGY

Reviews See A. J. Gray & D. M. Soderlund, Chapt. 5 in "Insecticides". FAO/WHO 89, 91 (see part 2 of the Bibliography). IARC ref. 53 class 3 Oral Acute oral LD50 for rats ranges from 135->5000 mg/kg, depending upon carrier and conditions of the study; for dogs >300 mg/kg. Acute oral LD50 for formulations in rats: >2000 mg (of 15 g/l EC)/kg; 445 mg (of 25 g/l EC)/kg; >5000 mg (of 5 g/l UL)/kg; >16 000 mg (of 25 g/kg WP)/kg; >40 000 mg (of 25 g/l SC)/kg. Skin and eye Acute percutaneous LD50 for rats and rabbits >2000 mg/kg. Non-irritating to skin; mild eye irritant (rabbits). Inhalation LC50 (4 h) for rats 2.2 mg/l air; (1 h) >4.6 mg/l air (micronised). NOEL (2 y) for mice 12, rats 1, dogs 1 mg/kg b.w. ADI (JMPR) 0.01 mg/kg b.w. [2000]. Other Non-mutagenic and non-teratogenic (mice, rats, rabbits). Toxicity class WHO (a.i.) II; EPA (formulation) II

ECOTOXICOLOGY

Birds Acute oral LD50 for mallard ducks >4640 mg/kg. Dietary LC50 (8 d) for mallard ducks >8039, quail >5620 mg/kg diet. NOEL for reproduction for mallard ducks >70, bobwhite quail >55 mg/kg daily. Fish Toxic to fish under laboratory conditions; LC50 (96 h) for rainbow trout 0.91, bluegill sunfish 1.4 ?g/l. Not toxic to fish under natural conditions. Daphnia LC50 (48 h) 3.5 ?g/l. Algae EC50 (96 h) for algae (Selenastrum capricornutum) >9.1 mg/l. Low LD50 and LC50 values under laboratory conditions do not represent a significant hazard to aquatic fauna in normal field use. Bees Toxic to bees, LD50 (oral) 79 ng/bee; (contact) 51 ng/bee. Low LD50 and LC50 values under laboratory conditions do not represent a significant hazard to bees in normal field use. Worms LC50 (14 d) for earthworms >1290 mg/kg soil.

ENVIRONMENTAL FATE

EHC 97 (WHO, 1990). Animals In rats, following oral administration, elimination occurs within 2-4 days. The phenyl ring is hydroxylated, the ester bond hydrolysed, and the acid moiety is eliminated as the glucuronide and glycine conjugates. Plants No uptake through leaves and roots - non-systemic compound. No major metabolites, except in oily crops, where trans-deltamethrin is part of the residue definition. Soil/Environment In soil, undergoes microbial degradation within 1-2 weeks. Kd 3790-30 000, Koc 4.6 ??105-1.63 ??107 cm3/g, confirms strong adsorption by soil colloids and no risk of leaching. DT50 (lab., aerobic) 21-25 d, (anaerobic) 31-36 d. In field, DT50 <23 d. Soil photolysis DT50 9 d. No incidence on soil microflora and nitrogen cycle.