The development of chemicals to selectively control the growth of weeds has been a fascinating success story which has unfolded largely during the last four decades. The dramatic growth of herbicide research that followed the wartime discoveries of the auxin-type herbicides (phenoxyalkanoic acids) resulted in a whole range of compounds and mixtures which are used to eliminate broad-or narrow-leaved weeds from agricultural, horticul- tural, or forestry crops. Today, the safe use of this armament of compounds requires our understanding of their mode of action, metabolism, and environmental...