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Published online by Cambridge University Press: 12 June 2017
Producers of food have always been troubled with weeds. Hand labor was the primary source of weed control for centuries, and selective weed control was not achieved until copper sulphate was used to control mustard (Brassica spp.) in wheat (Triticum aestivum L.) in 1896 (4, 42). Adequate crop selectivity was usually difficult to obtain with herbicides during the first 40 yr of the 20th century and the cost of the early herbicides was high.