ABSTRACT
The use of chemicals by man to control unwanted vegetation dates back several centuries, but modern chemical weed management essentially began with the discovery of the hormonelike herbicides in the 1940s. The first hormonelike herbicides developed were the substituted phenoxyacetic acids. The phenoxyacetic acid herbicides were discovered quite by accident as a result of research being conducted concurrently in the United States and England to develop synthetic organic compounds that mimicked the biological activity of auxins (Kirby, 1980). Development and use of 2,4-D, MCPA, and related hormonelike herbicides to control broadleaf weeds in cereal grains ushered in a new era of chemical weed management after World War II. It was during the 1950s and 1960s that the modern practice of using relatively low rates of synthetic herbicides for selective weed control in field crops was widely adopted in developed countries of the world.
