Herbicides, also commonly known as weed killers, are substances used to control undesired plants, also known as weeds. Selective herbicides control specific weed species while leaving the desired crop relatively unharmed, while non-selective herbicides kill plants indiscriminately. The combined effects of herbicides, nitrogen fertilizer, and improved cultivars has increased yields of major crops by three to six times from 1900 to 2000.
Weed control is a type of pest control, which attempts to stop or reduce growth of weeds, especially noxious weeds, with the aim of reducing their competition with desired flora and fauna including domesticated plants and livestock, and in natural settings preventing non native species competing with native species.
Glyphosate is a broad-spectrum systemic herbicide and crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSP). It is used to kill weeds, especially annual broadleaf weeds and grasses that compete with crops. Its herbicidal effectiveness was discovered by Monsanto chemist John E. Franz in 1970. Monsanto brought it to market for agricultural use in 1974 under the trade name Roundup. Monsanto's last commercially relevant United States patent expired in 2000.
Paraquat (trivial name; ), or N,N′-dimethyl-4,4′-bipyridinium dichloride (systematic name), also known as methyl viologen, is a toxic organic compound with the chemical formula [(C6H7N)2]Cl2. It is classified as a viologen, a family of redox-active heterocycles of similar structure. This salt is one of the most widely used herbicides worldwide. It is quick-acting and non-selective, killing green plant tissue on contact. It is also toxic (lethal) to human beings and animals. Its lethality is attributed to its enhancing production of superoxide anions. It has been linked to the development of Parkinson's disease.
Picloram is a systemic herbicide used for general woody plant control. It also controls a wide range of broad-leaved weeds, but most grasses are resistant. A chlorinated derivative of picolinic acid, picloram is in the pyridine family of herbicides.
Phenoxy herbicides are two families of chemicals that have been developed as commercially important herbicides, widely used in agriculture. They share the part structure of phenoxyacetic acid.
Glufosinate is a naturally occurring broad-spectrum herbicide produced by several species of Streptomyces soil bacteria. Glufosinate is a non-selective, contact herbicide, with some systemic action. Plants may also metabolize bialaphos and phosalacine, other naturally occurring herbicides, directly into glufosinate. The compound irreversibly inhibits glutamine synthetase, an enzyme necessary for the production of glutamine and for ammonia detoxification, giving it antibacterial, antifungal and herbicidal properties. Application of glufosinate to plants leads to reduced glutamine and elevated ammonia levels in tissues, halting photosynthesis and resulting in plant death.
Fenthion is an organothiophosphate insecticide, avicide, and acaricide. Like most other organophosphates, its mode of action is via cholinesterase inhibition. Due to its relatively low toxicity towards humans and mammals, fenthion is listed as moderately toxic compound in U.S. Environmental Protection Agency and World Health Organization toxicity class.
Pendimethalin is an herbicide of the dinitroaniline class used premergently and postemergently to control annual grasses and certain broadleaf weeds. It inhibits cell division and cell elongation. Pendimethalin is a K1-group according to the Herbicide Resistance Action Committee (HRAC) classification and is approved in Europe, North America, South America, Africa, Asia and Oceania for different crops including cereals, corn, soybeans, rice, potato, legumes, fruits, vegetables, and nuts, plus lawns and ornamental plants.
The environmental effects of pesticides describe the broad series of consequences of using pesticides. The unintended consequences of pesticides is one of the main drivers of the negative impact of modern industrial agriculture on the environment. Pesticides, because they are toxic chemicals meant to kill pest species, can affect non-target species, such as plants, animals and humans. Over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species, because they are sprayed or spread across entire agricultural fields. Other agrochemicals, such as fertilizers, can also have negative effects on the environment.
Bromoxynil is an organic compound with the formula HOBr2C6H2CN. It is classified as a nitrile herbicide, and as such sold under many trade names. It is a white solid. It works by inhibiting photosynthesis. It is moderately toxic to mammals.
Trifluralin is a common pre-emergent selective herbicide, a dinitroaniline. With about 14 million pounds (6,400 t) used in the United States in 2001, and 3–7 million pounds (1,400–3,200 t) in 2012, it is one of the most widely used herbicides. Trifluralin is also used in Australia, and New Zealand. Introduced in 1964, Trifluralin was the first organofluorine compound used as an agrochemical.
Monolinuron is a pesticide, more specifically a selective systemic herbicide and an algaecide. As an herbicide, it is used to control broad-leaved weeds and annual grasses in vegetable crops such as leeks, potatoes, and dwarf French beans. Monolinuron affects the photosynthesis in weeds. Following uptake of monolinuron through roots and leaves of weeds, monolinuron causes early symptoms of yellowing and die-back of the leaves, eventually resulting in weed death. In fishkeeping, it is used to control blanket weed and hair algae.
Lactofen is a complex ester of acifluorfen and is a nitrophenyl ether selective herbicide and fungicide. It is used in postemergence applications to certain crops which are resistant to its action. The name "Lactofen" is approved by the American National Standards Institute and the Weed Science Society of America, and is also approved in China (乳氟禾草灵).
2,4-Dichlorophenoxyacetic acid is an organic compound with the chemical formula Cl2C6H3OCH2CO2H. It is usually referred to by its ISO common name 2,4-D. It is a systemic herbicide that kills most broadleaf weeds by causing uncontrolled growth, but most grasses such as cereals, lawn turf, and grassland are relatively unaffected.
Bentazon is a chemical manufactured by BASF Chemicals for use in herbicides. It is categorized under the thiadiazine group of chemicals. Sodium bentazon is available commercially and appears slightly brown in colour.
Butafenacil is the ISO common name for an organic compound of the pyrimidinedione chemical class used as an herbicide. It acts by inhibiting the enzyme protoporphyrinogen oxidase to control broadleaf and some grass weeds in crops including cereals and canola.
Prosulfocarb is a pre-emergent herbicide used agriculturally in Australia, the EU, Japan, New Zealand,, Morocco and Iran, for control of annual ryegrass and toad rush in wheat and barley crops. It was introduced to the EU in 1988 and is rapidly growing in use, with sales increasing by over 500% in France since 2008.
Diflufenican is a herbicide used to control weeds including wild radish and wild turnip weeds or suppress capeweed, crassula, marshmallow or shepherd's purse, in clover pasture, lupins, lentils or field peas. It has seen use in Australia, Europe, and in Feb 2024 registered in North America by the PMRA, EPA registration pending, for use on soybean and corn.
Isoproturon (IPU) is a urea class selective herbicide, which has been used to control annual grasses and many broad leafed weeds in wheat, barley, rye and triticale.
