Neonicotinoid insecticides were considered safe when they were introduced because their toxicity to mammals is far lower than it is to insects. These compounds act on the central nervous system of insects. Imidacloprid is not only the leading neonicotinoid, but it is the world’s most widely used insecticide. The US Environmental Protection Agency granted the first imidacloprid registration to Miles Laboratories (now Bayer CropScience) in 1994 for use on turfgrass and ornamentals.
In recent years, the declining population of honeybees and other beneficial insects in the United States and Europe has been attributed to the widespread use of imidacloprid. The EPA and other authorities have restricted the use of imidacloprid and other neonicotinoids in areas where bees are known to be active.
Imidacloprid may present another threat. A study by C. A. Hallmann and co-workers at Radboud University in the Netherlands found that neonicotinoids may be indirectly responsible for the decline in populations of insect-eating birds. The declines began when imidacloprid was introduced in the 1990s.
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