Pesticides used to kill or control the growth of weeds are called herbicides. The beginnings of chemical weed control in fields can be traced back to the late 19th century, in the control of European grape downy mildew, Bordeaux liquor was occasionally found to harm some cruciferous weeds but not cereal crops. France, Germany, the United States at the same time found sulfuric acid and copper sulfate weed action, and used in wheat and other places weed. The organic chemical herbicide period began with the discovery of the selective herbicide dinitrophenol in 1932. The emergence of 2, 4-drops in the 1940s greatly promoted the rapid development of the organic herbicide industry. Glyphosate synthesized in 1971 is a major breakthrough in organophosphorus herbicides, which has the characteristics of wide insecticidal spectrum and no pollution to the environment. In addition, the emergence of a variety of new dosage forms and new technology has greatly improved the effect of weeding. In 1980, herbicides accounted for 41% of the total sales of pesticides in the world, surpassing pesticides and ranking first. After that, the development of herbicides in the world gradually stabilized, the main development of efficient, low-toxicity, broad-spectrum, low-dosage varieties, and disposable treatment agents with little environmental pollution gradually became the mainstream.

Herbicides can be classified according to the mode of action, application site, compound source and so on. Sodium chlorate, borax, arsenic, trichloroacetic acid have a dieback effect on any kind of plant, but because of their residual effects, they can not be used in the field. Selective herbicides, especially nitrophenol, chlorophenol and carbamic acid derivatives, most of which are effective, including O-isopropy-N-phe-nylcarbamate, abbreviated IPC:C6H5NHCOOCH-(CH3)2], O-isopropy-N-phenylcarbamic acid, IPC: C6H5NHCOOch -(CH3)2. dinitro-O-cresylate (sodium dinitro-o-Cresylate). The most famous herbicide with auxin action is 2, 4-D, which is thought to disrupt the hormonal balance in plants and cause physiological disorders, but it is a very effective herbicide for plants other than grasses. It is generally believed that this selectivity is determined by the intensity of the detoxification of 2, 4-D by the plant species, or because the concentration of 2, 4-D varies by plant species.