NOMENCLATURE

Common name thiamethoxam (BSI, pa ISO)

IUPAC name 3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro)amine 

Chemical Abstracts name 3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro-4H-1,3,5-oxadiazin-4-imine 

CAS RN [153719-23-4]  Development codes CGA 293343 (Ciba-Geigy) 

PHYSICAL CHEMISTRY

Mol. wt. 291.7  M.f. C₈H₁₀ClN₅O₃S  Form Crystalline powder.  M.p. 139.1 °C  V.p. 6.6 ´ 10^-6 mPa (25 °C)  K_OW logP = -0.13 (25 °C)  Henry 4.70 ´ 10^-10 Pa m³ mol^-1 (calc.)  Solubility In water 4.1 g/l (25 °C). 

APPLICATIONS

Biochemistry Agonist of the nicotinic acetylcholine receptor, affecting the synapses in the insect central nervous system.  Mode of action Insecticide with contact, stomach and systemic activity. Rapidly taken up into the plant and transported acropetally in the xylem.  Uses Under develoment for control of aphids, whitefly, thrips, ricehoppers, ricebugs, mealybugs, white grubs, Colorado potato beetle, flea beetles, wireworms, ground beetles, leaf miners and some lepidopterous species, at application rates from 10 to 200 g/ha (R. Senn et al., loc. cit.). Major crops for foliar and soil treatments are cole crops, leafy and fruity vegetables, potatoes, rice, cotton, deciduous fruit, citrus, tobacco and soya beans; for seed treatment use, maize, sorghum, cereals, sugar beet, oilseed rape, cotton, peas, beans, sunflowers, rice and potatoes.  Formulation types FS; GR, SC, WG, WS

MAMMALIAN TOXICOLOGY

Oral Acute oral LD₅₀ for rats 1563 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).  Inhalation LC₅₀ (4 h) for rats >3720 mg/m³.  Toxicity class WHO (a.i.) III 

ECOTOXICOLOGY

Birds Acute oral LD₅₀ for bobwhite quail 1552, mallard ducks 576 mg/kg. Dietary LC₅₀ for bobwhite quail and mallard ducks >5200 mg/kg.  Fish LC₅₀ (96 h) for rainbow trout >100, bluegill sunfish >114, sheepshead minnow >111 mg/l.  Daphnia EC₅₀ (48 h) >100 mg/l.  Algae EC₅₀ (96 h) for green algae >100 mg/l.  Other aquatic spp. LC₅₀ (96 h) for mysid shrimp 6.9 mg/l; EC₅₀ (96 h) for Eastern oyster >119 mg/l.  Bees LD₅₀ for honeybees (contact) 0.024 mg/bee.  Worms LC₅₀ (14 d) for Eisenia foetida >1000 mg/kg soil.

ENVIRONMENTAL FATE

Animals Quickly and completely absorbed, rapidly distributed in the body and rapidly eliminated. The toxicokinetics and metabolism are not influenced by the route of administration, the dose level, pre-treatment, the site of label or the sex of animals. The major metabolic pathways are essentially the same in rats as in mice, goats and hens.  Plants Degradation/metabolism has been studied in 6 different crops with soil, foliar and seed treatment application. The qualitative metabolic pattern was similar for all types of applications and for all studied crops.  Soil/Environment Soil DT₅₀ (median) 51 d. Stable in water under acid conditions, hydrolysed under alkaline conditions. Aqueous photolysis occurs rapidly. No bioaccumulation.