History and Early Investigation of Mode of Action of Peroxidizing Herbicides

Abstract

In this chapter, the history of diphenyl ether (DPE) herbicides, which became the starting structures of present peroxidizing herbicides, and the early investigations of this herbicide group in Japan will be reviewed. First, chemical weeding in rice cultivation in the 1960s in Japan will be discussed, when pentachlorophenol (PCP) followed by phenoxy herbicides was commonly used. However, after severe fish damage by PCP, nitrofen and chloronitrofen were selected as low fish-toxicity herbicides. This was the beginning of the practical usage of DPE herbicides. There are two types of DPE herbicides. The special herbicidal activities of ortho-substituted DPE herbicides, especially the light requirement for the activity, will be explained in detail. Although the chemical structures are quite different from diphenyl ethers, oxadiazon, phenopylate and cyclic imides, they exhibit the same mode of action, which led to many kinds of peroxidizing herbicides. As an appendix, the larvicidal activity of DPEs on mosquitoes which seemed to contribute the control of Japanese sleeping sickness (Japanese encephalitis) mediated by mosquitoes in Japan will be discussed.