Chemical Properties
Off-White to Pale Yellow Solid
Uses
Thiamethoxam is a broad spectrum insecticide active against a
wide spectrum of sucking and chewing insect pests after foliar, soil or
seed treatment.
Definition
ChEBI: Thiamethoxam is an oxadiazane that is tetrahydro-N-nitro-4H-1,3,5-oxadiazin-4-imine bearing (2-chloro-1,3-thiazol-5-yl)methyl and methyl substituents at positions 3 and 5 respectively. It has a role as an antifeedant, a carcinogenic agent, an environmental contaminant, a xenobiotic and a neonicotinoid insectide. It is an oxadiazane, a member of 1,3-thiazoles, an organochlorine compound and a 2-nitroguanidine derivative. It derives from a 2-chlorothiazole.
Application
Thiamethoxam is a neonicotinoid insecticide that is used widely in Wisconsin. Thiamethoxam is the active ingredient in a variety of products used in agriculture to kill sucking and chewing insects that feed 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 like 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 show that when exposed to neonicotinid pesticides honeybees have probelms returnign home after foraging and bumblebee colonies grow poorly and produce fewer queens.
Flammability and Explosibility
Flammable
Metabolic pathway
All the information on thiamethoxam is taken from a summary of the
proceedings of meeting published by the manufacturer. Full experimental
details are not given in the report and the identity of metabolites is not
disclosed (Novartis, 1997).
Degradation
Thiamethoxam is hydrolytically stable at pH 5 (half-life about 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 about 1 hour. In
aquatic systems, degradation occurs under alkaline conditions and the
insecticide is rapidly photodegraded but not readily biodegraded
(Novartis, 1997).
Mode of action
Thiamethoxam interferes with nicotinic acetylcholine receptors in the insect’s nervous system, which are essential for proper functioning of the nerves. Within hours of contact or ingestion of thiamethoxam, insects stop feeding. Death usually occurs within 24 to 48 hours.
The activity of thiamethoxam, or any insecticide, at the target site is just one factor in its 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) has organized insecticides into 28 groups, plus sub-groups, based on their modes of action. Thiamethoxam is a Group 4A insecticide (neonicotinoids).
