allowed the analogue with X=CH3 (i.e. what became tefluthrin) to be identified after field trials as the optimum for development under the ICI code number PP993. It was first marketed in 1987 using the trademark Force. In 2000, the agrochemical business of ICI merged with that of Novartis to form Syngenta, which still manufactures and supplies tefluthrin. The US patent covering the parent compound expired in November 2002. Tefluthrin was registered for sale in the European Union until December 5, 2008, when it was added to a group of pesticides whose authorization was withdrawn and it could no longer be sold. However, on January 1, 2012, it was re-approved for use. Mechanism of action Pyrethroid insecticides, including tefluthrin, disrupt the functioning of the nervous system in an organism. They are fast-acting axonic excitotoxins, which affect the voltage-gated sodium channels. The sodium channels are heteromultimeric complexes consisting of one large 𝛼-subunit and two smaller 𝛽-subunits. The binding site of tefluthrin is on the 𝛼-subunit, which also forms the pore of the channel. It alters the functioning of the channel by blocking the inactivation and slowing the deactivation. This results in persistent and prolonged activation of sodium channels and inflow of sodium, which is lethal to the insect. There are many different forms of sodium channels: in mammals, nine different sodium channel 𝛼-subunits have been identified (named Nav1.1-Nav1.9). The channel isoforms differ in affinity for tefluthrin; for example the Nav1.6 is at least 15-fold more sensitive than the Nav1.2 isoform. Formulations Tefluthrin is made available to end-users only in formulated products. Its main use is for the control of soil-dwelling insects in maize when formulated as granules. It can also be incorporated in seed treatments. Usage All pesticides are required to seek registration from appropriate authorities in the country in which they will be used. In the United States, the Environmental Protection Agency (EPA) is responsible for regulating pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Food Quality Protection Act (FQPA). A pesticide can only be used legally according to the directions on the label that is included at the time of the sale of the pesticide. The purpose of the label is "to provide clear directions for effective product performance while minimizing risks to human health and the environment". A label is a legally binding document that mandates how the pesticide can and must be used and