Herbicides

Abstract

Herbicides represent about 60% of the pesticides used worldwide. Bioherbicides are a growing portion of the herbicides used, but the several hundred commercial synthetic herbicides represent most of the herbicide market. Since their introduction about 70 years ago, weed management has been dominated by synthetic herbicides because of their efficiency and economic benefits to farmers. These herbicides have only about 20 modes of action, and resistance has evolved to most of them. New modes of action are needed for resistance management, but only a single new herbicide mode of action has been introduced in the last 30 years. Crops made resistant to the nonselective herbicide glyphosate through transgene technology have helped to make glyphosate the most used herbicide worldwide, but evolution of glyphosate‐resistant weeds is reducing reliance on glyphosate. New technologies, such as precision agriculture, will reduce herbicide use in the future. Key Concepts Herbicides are the principal means of weed management worldwide. Most herbicides act by inhibiting the function of a single protein target (the mode of action). Weeds have evolved resistance to most herbicide classes. Crops made resistant to the herbicide glyphosate have played a dominant role in transgenic crops and in weed management. Herbicides with new modes of action are badly needed for herbicide resistance management.

Coexpression of I. variabilis-EPSPS* and WBceGO-B3S1 Genes Contributes to High Glyphosate Tolerance and Low Glyphosate Residues in Transgenic Rice

“…Glyphosate is a nonselective herbicide with high efficiency, low toxicity, and broad spectrum. It was applied industrially in the 1970s . With the emergence of glyphosate-resistant transgenic crops and changes in cultivation methods, the use of glyphosate has been increased by more than 100 times in recent years. , It has been reported that the extensive and continuous application of glyphosate has led to the emergence of 56 weeds that are resistant to glyphosate .…”

Action of the fungal compound citrinin, a bioherbicide candidate, on photosystem II

“…Bioherbicides are natural phytochemicals or living microorganisms that kill plants 5–7 . Because of their natural origin, bioherbicides are perceived as safer than synthetic herbicides.…”

C–P Natural Products as Next-Generation Herbicides: Chemistry and Biology of Glufosinate

“…2 A new MOA had been discovered and marked every 2−3 years from the 1950s to the 1980s, leading to the current use of a panel of commercial herbicides with approximately 20 known MOA. 3 Today, herbicides represent more than 50% of the pesticides (by volume) used worldwide, and modern agriculture, especially most large-scale and intensive crops, and farming systems rely almost exclusively on herbicides to control unwanted plants. 4 However, the intense selection pressure on the target weed created by the massive and repeated use of commercial herbicides with the same MOA over large farming areas has led to the slow-but-steady evolution of many herbicide-resistant weed biotypes, which has been heavily aggravated by the widespread use of glyphosate-resistant crops (GRCs) in the last 25 years.…”

“…Since the introduction of the first herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA), discovered by Dr. William Gladstone Templeman at Imperial Chemical Industries in 1941, herbicides have revolutionized the agrichemical industry and weed management . A new MOA had been discovered and marked every 2–3 years from the 1950s to the 1980s, leading to the current use of a panel of commercial herbicides with approximately 20 known MOA . Today, herbicides represent more than 50% of the pesticides (by volume) used worldwide, and modern agriculture, especially most large-scale and intensive crops, and farming systems rely almost exclusively on herbicides to control unwanted plants …”