Plant Biochemistry, Environmental Properties, and Global Impact of the Sulfonylurea Herbicides

The sulfonylurea herbicides are highly active, with use rates ranging from 2 - 75 g a. i./ha. They act by inhibition of acetolactate synthase (E. C. 4.1.3.18), and selectivity, based on rapid metabolic inactivation, has been discovered in wheat, barley, corn, soybeans, rice, oil rapeseed, and other crops. These herbicides are non-toxic to animals, do not accumulate in non-target organisms, are non-volatile, and degrade in soil by chemical and biological processes with half-lives of 1 - 8 weeks. To date, 15 sulfonylurea herbicides for use in diverse crops have been (or soon will be) commercialized, and their favorable agronomic and environmental properties have led to rapid acceptance in the marketplace. This chapter reviews the mode of action, crop selectivity mechanisms, and soil and environmental properties of these compounds, and outlines some aspects of their impact on global agriculture.