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.
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.
Alachlor is an herbicide from the chloroacetanilide family. It is an odorless, white solid. The greatest use of alachlor is for control of annual grasses and broadleaf weeds in crops. Use of alachlor is illegal in the European Union and no products containing alachlor are currently registered in the United States.
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.
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.
Sulfentrazone is the ISO common name for an organic compound used as a broad-spectrum herbicide. It acts by inhibiting the enzyme protoporphyrinogen oxidase. It was first marketed in the US in 1997 by FMC Corporation with the brand name Authority.
MCPB, 2,4-MCPB, 4-(4-chloro-o-tolyloxy)butyric acid (IUPAC), or 4-(4-chloro-2-methylphenoxy)butanoic acid (CAS) is a phenoxybutyric herbicide. In the United States it is registered for use on pea crops before flowering, for post-emergence control of broadleaf annual and perennial weeds including Canadian thistle, buttercup, mustard, purslane, ragweed, common lambsquarters, pigweed, smartweed, sowthistle, and morning glory. It has low to moderate acute toxicity, with kidney and liver effects as the main hazard concerns. It is not volatile, persistent, or likely to bioconcentrate.
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, previously in the EU. Introduced in 1964, Trifluralin was the first organofluorine compound used as an agrochemical.
Acifluorfen is the ISO common name for an organic compound used as an herbicide. It acts by inhibiting the enzyme protoporphyrinogen oxidase which is necessary for chlorophyll synthesis. Soybeans naturally have a high tolerance to acifluorfen and its salts, via metabolic disposal by glutathione S-transferase. It is effective against broadleaf weeds and grasses and is used agriculturally on fields growing soybeans, peanuts, peas, and rice.
Cyanazine is a herbicide that belongs to the group of triazines. Cyanazine inhibits photosynthesis and is therefore used as a herbicide.
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.
Nitralin is a selective pre-emergent dinitroaniline herbicide that is closely related to trifluralin, and released two years later in 1966. Today it is largely obsolete. It was used in the USA, France and Australia to control annual grasses and broad-leaved weeds, and was applied on vines, crops and turf.
Profluralin is a dinitroaniline herbicide used preëmergently to control annual grasses and broadleaf weeds, in cotton, soybeans, peanuts, sunflower, cabbage, cauliflower, tomato and others. Profluralin has largely fallen out of use. It rose out of the related, still in common use, trifluralin.
Ethalfluralin is a herbicide. It is a preëmergent dinitroaniline developed from trifluralin, used to control annual grasses and broad-leaved weeds. It was synthesised in 1971, first sold in Turkey in 1975, the United States in 1983. It is used on soybeans, peanuts, potatoes, and as of 2023, is the first conventional herbicide the EPA permits on hemp, as ethalfluralin leaves no residue in the plant. Ethalfluralin is not used domestically.
Isopropalin is a herbicide. Introduced in 1969, it is a preëmergent selective dinitroaniline to control annual grasses and broadleaf weeds. Brought by DowElanco in 1972 to the US and Australia, it is now considered obsolete. In 1974, American farmers used 250,000 pounds (110,000 kg) of isopropalin.
Chlornidine is a preemergent herbicide. It is a dinitroaniline used in China and India on soybeans, corn, cotton, sorghum, and peanuts.
Dipropalin is a preëmergent dinitroaniline herbicide. It is currenctly not commercially used in western countries, but may be available in China and used in India. It has low acute toxicity. It is used on turf. Tests in the 1960s in the USA evaluated its performance as a trifluralin analog, where it scored the highest pre-emergent effectiveness amongst methyl-group analogs, though losing to several trifluoromethyls, such as trifluralin itself. Dipropalin's methyl group does see increased post-emergent activity, but no trifluralin analog was effective in this regard.
Zytron, also known as DMPA, is a chlorophenoxy herbicide. It controls crabgrass and other weeds in turf preëmergently, and ants, chinch bugs and grubs. It is used on baseball pitches in Australia.
Dinitramine is a preëmergent dinitroaniline herbicide incorporated into soil to control weeds for months after. It is no longer approved in the U.S.A., and is not in the European Union, though in Iran it has been used to control annual grasses and broadleaf weeds in cotton and soybeans, as it was in the U.S. as of 1975, where it was also used on sunflower.
