Thiamethoxam

Melting point

139.1 °C

Boiling point

485.8 ± 55.0 °C (Predicted)

Density

1.71 ± 0.1 g/cm³ (Predicted)

Vapor pressure

6.6 × 10^-9 Pa (25 °C)

Storage temperature

Inert atmosphere, 2–8 °C

Solubility

DMSO: 250 mg/mL (857.02 mM)

Water solubility

4.1 × 10³ mg/L (25 °C)

Form

Solid

pKa

0.99 ± 0.10 (Predicted)

Color

Off-white to yellow

Hazard codes

Xn

Risk statements

22-50/53

Safety statements

22-61-60

RIDADR

UN 3077 9 / PGIII

WGK (Germany)

2

HS code

29341000

Hazardous substances data

153719-23-4 (Hazardous Substances Data)

Toxicity

LD50 in rats (mg/kg): 1563 (oral), >2000 (dermal); LD50 in bobwhite quail and mallard duck (mg/kg): 1552 and 576 (oral). LC50 (96 hr) in rainbow trout and bluegill (mg/L): >100 and >114 (Senn).

Chemical properties

Off-white to pale yellow solid

Uses

Thiamethoxam is a broad-spectrum insecticide active against a wide range of sucking and chewing insect pests following foliar, soil, or seed treatment.

Definition

ChEBI: Thiamethoxam is an oxadiazane bearing tetrahydro-N-nitro-4H-1,3,5-oxadiazin-4-imine, substituted with (2-chloro-1,3-thiazol-5-yl)methyl and methyl groups at positions 3 and 5, respectively. It acts as an antifeedant, a carcinogenic agent, an environmental contaminant, a xenobiotic, and a neonicotinoid insecticide. It is an oxadiazane, a member of 1,3-thiazoles, an organochlorine compound, and a 2-nitroguanidine derivative. It is derived from 2-chlorothiazole.

Application

Thiamethoxam is a neonicotinoid insecticide used widely. It is the active ingredient in a variety of agricultural products used to control sucking and chewing insects feeding on roots, leaves, and other plant tissues. Agricultural uses include soil and seed treatments, as well as leaf spraying for most row and vegetable crops such as corn, soybeans, snap beans, and potatoes.

It is also used to control insects in livestock pens, poultry houses, sod farms, golf courses, lawns, household plants, and tree nurseries. It was first registered by the U.S. Environmental Protection Agency in 1999. Reports indicate that exposure to neonicotinoid pesticides can cause honeybees to have difficulty returning home after foraging, and bumblebee colonies may grow poorly and produce fewer queens.

Flammability and explosibility

Flammable

Metabolic pathway

All information on thiamethoxam is taken from a summary of the proceedings of a meeting published by the manufacturer. Full experimental details are not provided in the report, and the identities of metabolites are not disclosed (Novartis, 1997).

Degradation

Thiamethoxam is hydrolytically stable at pH 5 (half-life approximately 200–300 days). The compound is more labile at pH 9, where the half-life is a few days. It is rapidly photodegraded, with a half-life of approximately 1 hour. In aquatic systems, degradation occurs under alkaline conditions; the insecticide is rapidly photodegraded but is not readily biodegradable (Novartis, 1997).

Mode of action

Thiamethoxam interferes with nicotinic acetylcholine receptors in the insect nervous system, which are essential for proper nerve function. Within hours of contact or ingestion, insects stop feeding. Death usually occurs within 24 to 48 hours.

The activity of thiamethoxam, or any insecticide, at the target site is only one factor affecting efficacy. When comparing insecticides, other variables—including how the compound interacts with the environment, the plant, and the insect—also contribute to its insecticidal mode of action.

The Insecticide Resistance Action Committee (IRAC) groups insecticides into 28 groups, plus sub-groups, based on their modes of action. Thiamethoxam is a Group 4A insecticide (neonicotinoids).