Herbicides have been widely and intensively used for rice recently in Japan. This is ascribed to the continuous improvement of herbicides, stimulated by the demand for saving labor. Several successive stages which contributed to the improvement are as follows: the introduction of phenoxy-herbicides, the development of PCP granules, the improvement of selectivity, the extension of the herbicide application period and broadening of spectra to be controlled, and the
development of herbicides against perennial weeds. Weeding labor has steadily decreased for the past three decades, in relation to the expansion of herbicide use. Herbicide use in rice, however, seems to have virtually reached a limit, although new, more effective and safer herbicides may replace the current ones.