Milestones in the Development of Herbicide Safeners*

The concept o f using chemical safeners to improve herbicide selectivity became widely known in 1969 with the introduction o f naphthalic anhydride (N A ) to improve the tolerance o f maize to thiocarbamate herbicides. Soon thereafter dichlormid was also developed as a safener for thiocarbamates in maize. At present there are at least eight different chemical safeners that have been developed commercially. Many o f these safeners have been most effec­ tive for chloroacetamide or thiocarbamate herbicides in m onocotyledonous crops such as maize or sorghum. Some are like dichlormid and have been developed as physiologically selec­ tive safeners that can be combined in the formulation with the herbicides. Others, like N A , are either less selective or less active in the soil and must be used as dressings on the crop seed. Most o f the presently used safeners are for soil active herbicides. The challenge for the future will be to develop safeners that are effective for the newer postemergence herbicides in dicoty­ ledonous as well as monocotyledonous crops.