pesticides >> Insecticides >> Abamectin

Abamectin

See also The BioPesticide Manual, 2nd Ed.

Insecticide, acaricide

avermectin

 

 

NOMENCLATURE

Common nameabamectin (BSI, draft E-ISO, ANSI); abamectine ((f) draft F-ISO)

IUPAC name(10E,14E,16E,22Z)-(1R,4S,5'S,6S,6'R,8R,12S,13S,20R,21R,24S)-6'-[(S)-sec-butyl]-21,24-dihydroxy-5',11,13,22-tetramethyl-2-oxo-3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene-6-spiro-2'-(5',6'-dihydro-2'H-pyran)-12-yl 2,6-dideoxy-4-O-(2,6-dideoxy-3-O-methyl-a-L-arabino-hexopyranosyl)-3-O-methyl-a-L-arabino-hexopyranoside (i) mixture with (10E,14E,16E,22Z)-(1R,4S,5'S,6S,6'R,8R,12S,13S,20R,21R,24S)-21,24-dihydroxy-6'-isopropyl-5',11,13,22-tetramethyl-2-oxo-3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene-6-spiro-2'-(5',6'-dihydro-2'H-pyran)-12-yl 2,6-dideoxy-4-O-(2,6-dideoxy-3-O-methyl-a-L-arabino-hexopyranosyl)-3-O-methyl-a-L-arabino-hexopyranoside (ii) (4:1)

Chemical Abstracts name5-O-demethylavermectin A1a(i) mixture with 5-O-demethyl-25-de(1-methylpropyl)-25-(1-methylethyl)avermectin A1a(ii)

Other namesavermectin B1CAS RN[71751-41-2] (abamectin); [65195-55-3] (i); [65195-56-4] (ii)EEC no.265-610-3 (avermectin B1a); 265-611-9 (avermectin B1b)Development codesMK-0936 (Merck); C-076 (Ciba); L-676,863

 

PHYSICAL CHEMISTRY

CompositionA mixture containing ³80% avermectin B1a(i) and £20% avermectin B1b(ii).Mol. wt.873.1 (avermectin B1a); 860.1 (avermectin B1b)M.f.C48H72O14(avermectin B1a); C47H70O14(avermectin B1b)FormColourless to pale yellow crystals.M.p.161.8-169.4 °C (decomp.)V.p.<3.7 ´ 10-3mPa (25 °C)KOWlogP = 4.4?.3 (pH 7.2, room temperature)Henry2.7 ´ 10-3Pa m3mol-1(25 °C)S.g./density1.18 (22 °C)SolubilityIn water 7-10 mg/l (20 ºC). In toluene 350, acetone 100, isopropanol 70, chloroform 25, ethanol 20, methanol 19.5, n-butanol 10, cyclohexane 6 (all in g/l, 21 ºC).StabilityStable to hydrolysis in aqueous solutions at pH 5, 7, and 9 (25 ºC). Sensitive to stronger acid and base. U.V. irradiation causes conversion first to the 8,9-Z- isomer, then to unidentified decomposition products.Specific rotation[a]D22+55.7?(c = 0.87 in CHCl3)

 

COMMERCIALISATION

ProductionIsolated from fermentation of Streptomyces avermitilis.HistoryAnthelmintic and acaricidal activity of a group of chemically related compounds, the avermectins, reported by I. Putter et al. (Experientia, 1981, 37, 963). A mixture of two of these, avermectin B1a(i) and avermectin B1b(ii) introduced in 1985 as an acaricide and insecticide by Merck Sharp & Dohme Agvet (now Syngenta AG).ManufacturersGilmore; Jingma; Sinon; Syngenta

 

APPLICATIONS

BiochemistryActs by stimulating the release of g-aminobutyric acid, an inhibitory neurotransmitter, thus causing paralysis. See M. J. Turner & J. M. Schaeffer in Ivermectin and Abamectin, W. C. Cambell ed., Springer-Verlag, New York (1989) p. 73.Mode of actionInsecticide and acaricide with contact and stomach action. Has limited plant systemic activity, but exhibits translaminar movement.UsesControl of motile stages of mites, leaf miners, suckers, Colorado beetles, etc. on ornamentals, cotton, citrus fruit, pome fruit, nut crops, vegetables, potatoes, and other crops. Application rates are 5.6 to 28 g/ha for mite control, 11 to 22 g/ha for control of leaf miners. Also used for control of fire ants.PhytotoxicityMay be phytotoxic to pome fruit when mixed with captan.Formulation typesEC.CompatibilityNot compatible with captan.Selected tradenames:'Agrimec' (Syngenta); 'Dynamec' (Syngenta); 'Vertimec' (Syngenta); 'Abacide' (Mauget); 'Gilmectin' (Gilmore); 'Satin' (Sanonda)

 

OTHER TRADENAMES

'Agri-Mek' (citrus) (Syngenta); 'Avid' (ornamentals) (Syngenta); 'Clinch' (Syngenta); 'Zephyr' (cotton) (Syngenta); 'Agrimectin' (Agro Chemicals); 'Belpromec' (Probelte); 'Green-Cyclone' (Zhuhai); 'Vapcomic' (Vapco) Discontinued names:'Affirm' * (Merck)

 

ANALYSIS

Product analysis by hplc with u.v. detection. Residues by conversion to a fluorescent product followed by hplc with fluorescence detection. See T. Wehner et al. in Comp. Anal. Profiles, Chapt. 4.

 

MAMMALIAN TOXICOLOGY

ReviewsFAO/WHO 74, 80, 82 (see part 2 of the Bibliography). G. Lankas & L. R. Gordon in Toxicology in Ivermectin and Abamectin, W. C. Campbell ed., Springer-Verlag (1989) pp. 89-112.OralAcute oral LD50for rats 10, mice 13.6 mg/kg (in sesame oil).Skin and eyeAcute percutaneous LD50for rabbits >2000 mg/kg. Mild eye irritant; non-irritating to skin (rabbits).ADI(JMPR) 0.002 mg/kg b.w. [1997] (for sum of abamectin and 8,9-Z- isomer); 0.001 mg/kg b.w. [1995] (for residues not containing D-8,9-isomer).OtherNon-mutagenic in the Ames test.Toxicity classEPA (formulation) IV

 

ECOTOXICOLOGY

BirdsAcute oral LD50for mallard ducks 84.6, bobwhite quail >2000 mg/kg.FishLC50(96 h) for rainbow trout 3.2, bluegill sunfish 9.6 mg/l.DaphniaEC50(48 h) 0.34 ppb.Algae>100 mg/l.Other aquatic spp.LC50(96 h) for pink shrimp (Panaeus duorarum) 1.6, blue crab (Callinectes sapidus) 153 ppb.BeesToxic to bees.WormsLC50(28 d) for earthworms 28 mg/kg soil.

 

ENVIRONMENTAL FATE

AnimalsRapidly eliminated (80-100% in 96 h), mainly via faeces; urinary excretion was 0.5-1.4%.PlantsDegradation/metabolism in each of three different plants is similar and occurs predominantly by photolysis on the plant surfaces. The definition of the residues is thus expressed as the combined residues of avermectin B1and its 8,9-Z-avermectin B1photoisomer.Soil/EnvironmentBinds tightly to soil, with rapid degradation by soil micro-organisms. No bioaccumulation.