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CAS number 153719-23-4 YesY
PubChem 5485188
ChemSpider 4588645 YesY
UNII 747IC8B487 YesY
KEGG C18513 YesY
Jmol-3D images Image 1
Molecular formula C8H10ClN5O3S
Molar mass 291.71 g mol−1
Density 1.57 g/cm3
Melting point 139.1 °C (282.4 °F; 412.2 K)
Solubility in water 4.1 g/L
R-phrases R22
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Thiamethoxam is an insecticide in the class of neonicotinoids. It has a broad spectrum of activity against many types of insects.


Thiamethoxam was developed by Syngenta but a patent dispute arose with Bayer which already had patents covering other neonicotinoids including imidacloprid. In 2002 the dispute was settled, with Syngenta paying Bayer $120 million in exchange for worldwide rights to thiamethoxam.[3][4]


Thiamethoxam is a systemic insecticide that is absorbed quickly by plants and transported to all parts of the plant, where it acts as a deterrent to insect feeding. It is active in the stomach of the insects, and also through direct contact. The compound interferes with information transfer between nerve cells, making the insects become paralyzed.

Thiamethoxam is effective against aphids, thrips, beetles, centipedes, millipedes, sawflies, leaf miners, stem borers and termites.

Syngenta asserts that thiamethoxam triggers various physiological reactions, which induce the expression of specific functional proteins involved in various stress defense mechanisms of the plant allowing it to better cope under tough growing conditions.[5]

Thiamethoxam is a moderately toxic substance. In normal use, there are no unacceptable risks involved. The substance is toxic to bees and harmful to aquatic and soil organisms, although the level of toxicity to bees is not yet clear. A metabolite of thiamethoxam in soil is clothianidin.

Banned by European Union in 2013[edit]

In 2012, several peer reviewed independent studies were published showing that several neonicotinoids had previously undetected routes of exposure affecting bees including through dust, pollen, and nectar; that sub-nanogram toxicity resulted in failure to return to the hive without immediate lethality, the primary symptom of colony collapse disorder; and showing environmental persistence in agricultural irrigation channels and soil. However, not all studies have found significant effects, and the studies carried out to date have not reached a clear conclusion on the impacts of neonicotinoids.[6] These reports prompted a formal peer review by the European Food Safety Authority, which stated in January 2013 that neonicotinoids pose an unacceptably high risk to bees, and that the industry-sponsored science upon which regulatory agencies' claims of safety have relied on may be flawed and contain several data gaps not previously considered.[7] In April 2013, the European Union voted for a two-year restriction on neonicotinoid insecticides. The ban will restrict the use of imidacloprid, clothianidin, and thiamethoxam for use on crops that are attractive to bees.[8]