Pymetrozin

NOMENCLATURE
Common name pymétrozine ((f) F-ISO); pymetrozine (BSI, E-ISO) IUPAC name (E)-4,5-dihydro-6-methyl-4-(3-pyridylmethyleneamino)-1,2,4-triazin-3(2H)-one
Chemical Abstracts name (E)-4,5-dihydro-6-methyl-4-[(3-pyridinylmethylene)amino]-1,2,4-triazin-3(2H)-one CAS RN [123312–89–0] 
PHYSICAL CHEMISTRY
Composition Tech. is ≥95% pure. Mol. wt. 217.2 M.f. C₁₀H₁₁N₅O Form Crystalline solid. M.p. 217 °C V.p. <4 × 10^-3 mPa (25 °C) (OECD 104) K_ow logP = –0.18 (OECD 107) Henry <3.0 × 10^-6 Pa m³ mol^-1 (calc.) S.g./density 1.36 (20 °C) Solubility In water 0.29 g/l (pH 6.5, 25 °C). In ethanol 2.4, hexane <0.001, toluene 0.034, dichloromethane 1.2, n-octanol 0.45, acetone 0.94, ethyl acetate 0.26 (all in g/l, 25 °C). Stability Stable in air (OECD 113/DTA). Hydrolysis DT₅₀ 5–12 d (pH 5); 616–800 d (pH 7); 510–1212 d (pH 9, 25 °C). pKa 4.06
APPLICATIONS
Biochemistry Novel, unidentified biochemistry. Mode of action Insecticide selective against Homoptera, causing them to stop feeding. Uses Control of aphids and whitefly in vegetables, potatoes, ornamentals, cotton, deciduous and citrus fruit, tobacco and hops; both juvenile and adult stages are susceptible. Also control of planthoppers in rice. Application rates vary from 150 g/ha on potatoes to 200–300 g/ha on ornamentals, tobacco and cotton; 10–30 g/hl on vegetables, fruit and hops. Formulation types DP; GR; WG; WP.
ENVIRONMENTAL FATE
Animals Extensively and rapidly absorbed (c. 90% in 24 h). Quickly and efficiently eliminated (mainly via excreta) and extensively metabolised in all species tested (rats, farm animals), without accumulation in most major animal food products. Metabolism is via oxidation of the methyl and triazine methylene, and cleavage between the triazine and pyridine rings. The metabolic pathways are similar for all species. Pymetrozine is the relevant residue for assessing the consumer exposure to treated animal food products. Plants The basic degradation steps are similar in all investigated crops; pymetrozine is the only relevant compound for residue definition. Soil/Environment In soils, very rapidly and strongly adsorbed; K_f 3.1–47.7 ml/g, K_oc 246–7875 ml/g o.c. (10 soils, mean 2245 ml/g o.c.); low mobility and low leaching potential. Soil DT₅₀ 2–69 d (field, 7 soils, median 14 d), DT₉₀ 55–288 d (field, 7 soils, median 185 d). Rapidly degraded in slightly acidic or sunlight-exposed surface water; DT₅₀ in surface water 5.2–6.6 d (lab., darkness, 2 water-sediment systems). Slightly volatile. In air, efficiently removed by direct photolysis and photochemically induced oxidation.
MAMMALIAN TOXICOLOGY
Oral Acute oral LD₅₀ for rats >5000 mg/kg. Skin and eye Acute percutaneous LD₅₀ for rats >2000 mg/kg. Non-irritating to skin and eyes (rabbits). Not a skin sensitiser (guinea pigs, M&K). Inhalation LC₅₀ (4 h) for rats >1800 mg/m³ air. NOEL (2 y) for rats 3.7 mg/kg b.w. daily; (90 d) for dogs 3 mg/kg b.w. daily; (1 y, oral) for dogs 5.33 mg/kg b.w.. daily. ADI (EC) 0.03 mg/kg b.w.; aRfD 0.1 mg/kg b.w. [2001]; (EPA) aRfD 0.01 mg/kg b.w. (females aged 13–49), 0.125 mg/kg b.w. (general population), cRfD 0.0038 mg/kg b.w. [2005]. Other Non-mutagenic in 5 assay tests. Toxicity class WHO (a.i.) III (company classification). EC classification R40| R52, R53 
ECOTOXICOLOGY
Birds Acute oral LD₅₀ for mallard ducks >2000 mg/kg. LC₅₀ (8 d) for bobwhite quail >5200 ppm. Fish LC₅₀ (96 h) for rainbow trout, sheepshead minnows and common carp >100 mg/l. Daphnia LC₅₀ (48 h) 87 mg/l. Algae LC₅₀ (72 h) for Scenedesmus subspicatus 47.1 mg/l; (5 d) for Selenastrum capricornutum 21.7 mg/l. Other aquatic spp. EC₅₀ (96 h) for eastern oysters 3.05 ppm. Bees LD₅₀ (48 h) (oral) >117 μg/bee; (contact) >200 μg/bee. Worms LC₅₀ (14 d) for Eisenia foetida 1098 mg/kg soil. Other beneficial spp. Harmless to Aleochara bilineata, Poecilus cupreus, Typhlodromus pyri, Aphidius matricariae and Chrysoperla carnea; slightly harmful to Orius insidiosus; moderately harmful to Aphidius colemani (IOBC).