One result of modern agriculture and its reliance upon herbicides is the emergence of weed populations that are resistant to herbicides. All natural weed populations, regardless of the application of any herbicide, probably contain individual plants (biotypes) that are resistant to herbicides. Repeated use of any herbicide will expose weed populations to selection pressure that may lead to an increase in the number of surviving, resistant individuals in the population. Consequently, the resistant weed population may increase to the degree that adequate weed control cannot be achieved via the application of that herbicide. Through their effective use in combination with other weed control practices, herbicides are today, and will remain, an integral part of food production.