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Interesting Facts:

-       Herbicides are the most widely used class of pesticides in the world accounting for 44% of all sales in 1988 (Conko, 2002).

-        Weeds are estimated to cause more than $40 billion in annual global agricultural losses (Conko, 2002).

            Herbicides and pest control have been around for hundreds of years. The first documented uses of herbicides occurred about 200 years ago, but even before that natural processes of genetic selection by farmers provided some resistant to weeds. The 1^st commercial selective broadleaf weed herbicides  (2.4-D and MCPA) came onto the market in 1945 and 1946 respectively. Reasoning behind the emergence of the herbicides at that time included wartime resource allocation (Liebman, 1993). During the war, resources were concentrated on supplies needed directly for the armed services and agriculture lost a great deal of support. Therefore, new ways of producing the same yield had to be established.

            Herbicides have experienced a great industrial growth up through the 1970’s. In the 1970’s herbicides experienced a growth of 6.3%, in the 80’s 2.2%, and in the 90’s 0.1%. The slow decline of production of new herbicides was due in part to the identification of new active agents in the chemical make-up of the herbicides (Tilman, 2002).

SDS occurring in Soybeans

Permissiong pending from http://www/agronomyday.cropsci.uiuc.edu/ 2001/tours/roundup-ready/

Classifying Herbicides

            Numerous systems have emerged to classify both herbicides and pesticides. Many classifications divide each substance by its biological means of attacking the desired weed or insect responsible for the deterioration of the chosen organism (Gunsolus, 1999). The overall route in which herbicides affect the cellular biology of a plant is called the Mode-of-Action. In a summery written by Merill A. Ross, professor of Weed Science, and Daniel K. Childs, an Extension Weed Specialist, in the Department of botany and Plant Pathology at Purdue University organize herbicides into two different groups by the manner in which they are applied to the plant. An herbicide can either be applied to the foliage or directly to the surrounding soil (Herbicide Handbook, 1994).

            Examples of foliage-applied herbicides include: Auxin Growth Regulators, Amino Acid Inhibitors, and Chlorophyll/ Carotenoid Inhibitors. Examples of soil-applied herbicides include: Root Inhibitors and Shoot Inhibitors (Ross, 2001). To see all the classifications of herbicides and their chemical and common names go to The Department of Botany at Purdue University website.