NOMENCLATURE

emamectin benzoate

CAS RN [155569-91-8]; formerly [137512-74-4] and [179607-18-2]  Development codes MK 244 (Merck) 

emamectin

Common name emamectin (BSI, pa E-ISO, ANSI); emamectine ((f) pa F-ISO)

IUPAC name A mixture containing 90% of (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[15.6.1.1^4,8.0^20,24]pentacosa-10,14,16,22-tetraene-6-spiro-2'-(5',6'-dihydro-2'H-pyran)-12-yl 2,6-dideoxy-3-O-methyl-4-O-(2,4,6-trideoxy-3-O-methyl-4-methylamino-a-L-lyxo-hexopyranosyl)-a-L-arabino-hexopyranoside and 10% of (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[15.6.1.1^4,8.0^20,24]pentacosa-10,14,16,22-tetraene-6-spiro-2'-(5',6'-dihydro-2'H-pyran)-12-yl 2,6-dideoxy-3-O-methyl-4-O-(2,4,6-trideoxy-3-O-methyl-4-methylamino-a-L-lyxo-hexopyranosyl)-a-L-arabino-hexopyranoside 

Chemical Abstracts name (4"R)-5-O-demethyl-4"-deoxy-4"-(methylamino)avermectin A_1a + (4"R)-5-O-demethyl-25-de(1-methylpropyl)-4"-deoxy-4"-(methylamino)-25-(1-methylethyl)avermectin A_1a (9:1) 

CAS RN [119791-41-2]; formerly [123997-28-4] and [137335-79-6] 

PHYSICAL CHEMISTRY

emamectin benzoate

Composition A mixture of emamectin B_1a (³90%) and emamectin B_1b (£10%), as their benzoate salts.  Mol. wt. 1008.3 (B_1a); 994.2 (B_1b)  M.f. C₅₆H₈₁NO₁₅ (B_1a); C₅₅H₇₉NO₁₅ (B_1b)  Form White to off-white powder.  M.p. 141-146 °C  V.p. 4 ´ 10^-3 mPa (21 °C)  K_OW logP = 5.0 (pH 7)  S.g./density 1.20 (23 °C)  Solubility In water 0.024 g/l (pH 7, 25°C). 

emamectin

Mol. wt. 886.1 (B_1a); 872.1 (B_1b)  M.f. C₄₉H₇₅NO₁₃ (B_1a); C₄₈H₇₃NO₁₃ (B_1b) 

COMMERCIALISATION

History Discovery and initial development was by Merck & Co., Inc. (now Syngenta AG). First sales in Israel and Japan in 1997.  Manufacturers Merck & Co.

APPLICATIONS

emamectin benzoate

Mode of action Non-systemic insecticide which penetrates leaf tissues by translaminar movement.  Uses For control of Lepidoptera on vegetables, brassicas and cotton, at up to 16 g/ha, and in pine trees, at 5-25 g/ha.  Formulation types EC; SG. 

ANALYSIS

Product and residues determined by hplc. Details available from Syngenta. 

MAMMALIAN TOXICOLOGY

emamectin benzoate

Oral Acute oral LD₅₀ for rats 76-89 mg/kg.  Skin and eye Acute dermal LD₅₀ for rabbits >2000 mg/kg. It is not irritant to skin, and has no sensitising potential.  Inhalation LC₅₀ (4 h) for rats 2.12-4.44 mg/m³.  NOEL (1 y) for dogs 0.25 mg/kg b.w.  ADI 0.0025 mg/kg.  Other Not tumorigenic.  Toxicity class WHO (a.i.) II 

ECOTOXICOLOGY

emamectin benzoate

Birds Acute oral LD₅₀ for mallard ducks 46, bobwhite quail 264 mg/kg. Dietary LC₅₀ (8 d) for mallard ducks 570, bobwhite quail 1318 ppm.  Fish LC₅₀ (96 h) for rainbow trout 174, sheepshead minnow 1430 mg/l.  Daphnia LC₅₀ 0.99 mg/l.  Algae >94 mg/l.  Bees Toxic to bees.  Worms >1000 mg/kg. 

ENVIRONMENTAL FATE

Animals Emamectin benzoate is partially metabolised but rapidly cleared (DT₅₀ following oral dosing 34-51 h), indicating that it has no potential for bioaccumulation.  Plants Metabolism has been investigated in lettuce, cabbage and sweet corn. It is non-systemic, and rapidly degrades in sunlight to various complex residues in which undegraded parent is the only significant residue. The residues were very low.  Soil/Environment Rapidly degraded