The insecticide methomyl ( S -methyl N -(methylcarbamoyloxy)thioacetimidate;
CAS 16752-77-5; Fig. 1 ) was fi rst introduced by E.I. du Pont de Nemours in 1968
(US EPA, 1998b ) . In 1978, the US Environmental Protection Agency classi fi ed
methomyl as a restricted-use pesticide (RUP; US EPA 1998a ) ; currently 15 registered
products are categorized as such (US EPA 1998b ) . Further restrictions were
implemented in 1995, limiting use to certain agricultural production areas, requiring
addition of an embittering agent during formulation and requiring the use of bait
stations (US EPA 1998a ) . Within the USA, approx. 262,000 kg of methomyl (a.i.)
was applied on agricultural crops annually from 1999 to 2004 (US EPA 2010 ) .
However, estimates for the period between 2001 and 2007 show annual average
usage of approx. 363,000 kg (a.i.); major crop uses included sweet corn, lettuce,
onions, and tomatoes (US EPA 2010 ) . In 2007, some 227,711 kg of active ingredient
was applied in California alone (CDPR 2007 ) .