Herbicide

herbicidesherbicidalweed killerweedkillersystemic herbicideweedkillerschemicalChemical controlchemical controlsflame weeding
Herbicides, also commonly known as weedkillers, are chemical substances used to control unwanted plants.wikipedia
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Pesticide resistance

insecticide resistanceresistanceherbicide resistance
Due to herbicide resistance - a major concern in agriculture - a number of products combine herbicides with different means of action.
As of 2014, few new weed killers are near commercialization, and none with a novel, resistance-free mode of action.

Atrazine

Altrazine
The triazine family of herbicides, which includes atrazine, were introduced in the 1950s; they have the current distinction of being the herbicide family of greatest concern regarding groundwater contamination.
Atrazine is a herbicide of the triazine class.

Glyphosate

Roundupglycosphateglyphosates
Glyphosate (Roundup) was introduced in 1974 for nonselective weed control. EPSPS inhibitors: Enolpyruvylshikimate 3-phosphate synthase enzyme (EPSPS) is used in the synthesis of the amino acids tryptophan, phenylalanine and tyrosine. They affect grasses and dicots alike. Glyphosate (Roundup) is a systemic EPSPS inhibitor inactivated by soil contact.
Glyphosate (IUPAC name: N-(phosphonomethyl)glycine) is a broad-spectrum systemic herbicide and crop desiccant.

Defoliant

defoliationdefoliantsdefoliate
Defoliant, similar to herbicides, but designed to remove foliage (leaves) rather than kill the plant.
A defoliant is any herbicidal chemical sprayed or dusted on plants to cause their leaves to fall off.

Imazaquin

imidazolinone
ALS inhibitors: the acetolactate synthase (ALS) enzyme (also known as acetohydroxyacid synthase, or AHAS) is the first step in the synthesis of the branched-chain amino acids (valine, leucine, and isoleucine). These herbicides slowly starve affected plants of these amino acids, which eventually leads to inhibition of DNA synthesis. They affect grasses and dicots alike. The ALS inhibitor family includes various sulfonylureas (SUs) (such as Flazasulfuron and Metsulfuron-methyl), imidazolinones (IMIs), s (TPs), pyrimidinyl oxybenzoates (POBs), and sulfonylamino carbonyl triazolinones (SCTs). The ALS biological pathway exists only in plants and not animals, thus making the ALS-inhibitors among the safest herbicides.
Imazaquin is an imidazolinone herbicide that effectively controls a broad spectrum of weed species.

Herbicidal warfare

anticrop agentused in warfare and conflict
Herbicides have also been used in warfare and conflict.
During the Malayan Emergency, Britain was the first nation to employ herbicides and defoliants in order to deprive the communist insurgents of cover and targeting food crops as part of the starvation campaign in the early 1950s.

Sulfonylurea

sulfonylureassulphonylureasulphonylureas
ALS inhibitors: the acetolactate synthase (ALS) enzyme (also known as acetohydroxyacid synthase, or AHAS) is the first step in the synthesis of the branched-chain amino acids (valine, leucine, and isoleucine). These herbicides slowly starve affected plants of these amino acids, which eventually leads to inhibition of DNA synthesis. They affect grasses and dicots alike. The ALS inhibitor family includes various sulfonylureas (SUs) (such as Flazasulfuron and Metsulfuron-methyl), imidazolinones (IMIs), s (TPs), pyrimidinyl oxybenzoates (POBs), and sulfonylamino carbonyl triazolinones (SCTs). The ALS biological pathway exists only in plants and not animals, thus making the ALS-inhibitors among the safest herbicides.
A number of sulfonylureas are also used as herbicides ("weedkiller"), because they can interfere with plant biosynthesis of certain amino acids.

Imperial Chemical Industries

ICIICI PharmaceuticalsImperial Chemical Industries (ICI)
The first modern herbicide, 2,4-D, was first discovered and synthesized by W. G. Templeman at Imperial Chemical Industries.
Early pesticide development included Gramoxone (1962, a herbicide), the insecticides pirimiphos-methyl in 1967 and pirimicarb in 1970, brodifacoum (a rodenticide) was developed in 1974; in the late 1970s, ICI was involved in the early development of synthetic pyrethroid insecticides such as lambda-cyhalothrin.

4-hydroxyphenylpyruvate dioxygenase inhibitor

HPPD inhibitors
HPPD inhibitors inhibit 4-Hydroxyphenylpyruvate dioxygenase, which are involved in tyrosine breakdown. Tyrosine breakdown products are used by plants to make carotenoids, which protect chlorophyll in plants from being destroyed by sunlight. If this happens, the plants turn white due to complete loss of chlorophyll, and the plants die. Mesotrione and sulcotrione are herbicides in this class; a drug, nitisinone, was discovered in the course of developing this class of herbicides.
4-Hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors (HPPD inhbitors) are a class of herbicides that prevent plants by blocking 4-Hydroxyphenylpyruvate dioxygenase, an enzyme in plants that breaks down the amino acid tyrosine into molecules that are then used by plants to create other molecules that plants need.

Diquat

diquat dibromideReglone
Photosystem I inhibitors steal electrons from the normal pathway through FeS to Fdx to NADP + leading to direct discharge of electrons on oxygen. As a result, reactive oxygen species are produced and oxidation reactions in excess of those normally tolerated by the cell occur, leading to plant death. Bipyridinium herbicides (such as diquat and paraquat) inhibit the FeS to Fdx step of that chain, while diphenyl ether herbicides (such as nitrofen, nitrofluorfen, and acifluorfen) inhibit the Fdx to NADP + step.
Diquat is a contact herbicide that produces desiccation and defoliation most often available as the dibromide, diquat dibromide.

Paraquat

methyl viologenparaquat dichlorideparaquat intoxication
Photosystem I inhibitors steal electrons from the normal pathway through FeS to Fdx to NADP + leading to direct discharge of electrons on oxygen. As a result, reactive oxygen species are produced and oxidation reactions in excess of those normally tolerated by the cell occur, leading to plant death. Bipyridinium herbicides (such as diquat and paraquat) inhibit the FeS to Fdx step of that chain, while diphenyl ether herbicides (such as nitrofen, nitrofluorfen, and acifluorfen) inhibit the Fdx to NADP + step.
This salt is one of the most widely used herbicides.

Auxin

auxinsrooting hormonerooting hormones
Synthetic auxins inaugurated the era of organic herbicides. They were discovered in the 1940s after a long study of the plant growth regulator auxin. Synthetic auxins mimic this plant hormone. They have several points of action on the cell membrane, and are effective in the control of dicot plants. 2,4-D is a synthetic auxin herbicide.
Some synthetic auxins, such as 2,4-D and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), are used also as herbicides.

Allelopathy

allelopathicallelochemicalsallelochemical
Some plants also produce their own natural herbicides, such as the genus Juglans (walnuts), or the tree of heaven; such action of natural herbicides, and other related chemical interactions, is called allelopathy.
This research furthers the possibility of using allelochemicals as growth regulators and natural herbicides, to promote sustainable agriculture.

Mesotrione

HPPD inhibitors inhibit 4-Hydroxyphenylpyruvate dioxygenase, which are involved in tyrosine breakdown. Tyrosine breakdown products are used by plants to make carotenoids, which protect chlorophyll in plants from being destroyed by sunlight. If this happens, the plants turn white due to complete loss of chlorophyll, and the plants die. Mesotrione and sulcotrione are herbicides in this class; a drug, nitisinone, was discovered in the course of developing this class of herbicides.
Mesotrione is an herbicide sold under the brand names Callisto and Tenacity that was brought to market by Syngenta in 2001.

Maize

corncorn (maize)Zea mays
It allowed for greatly enhanced weed control in wheat, maize (corn), rice, and similar cereal grass crops, because it kills dicots (broadleaf plants), but not most monocots (grasses).
Weeds are controlled through the use of herbicides, and no cultivation tillage is done during the growing season.

Agent Orange

defoliantAgent Orange § U.S. veterans class action lawsuit against manufacturersdefoliants
For instance, it led to 3 million Vietnamese people suffering health problems, one million birth defects caused directly by exposure to Agent Orange, and 24% of the area of Vietnam being defoliated.
Agent Orange is an herbicide and defoliant chemical, one of the "tactical use" Rainbow Herbicides.

Ailanthus altissima

tree of heavenailanthustree-of-heaven
Some plants also produce their own natural herbicides, such as the genus Juglans (walnuts), or the tree of heaven; such action of natural herbicides, and other related chemical interactions, is called allelopathy.
It involves the application of foliar or basal herbicides in order to kill existing trees, while either hand pulling or mowing seedlings in order to prevent new growth.

EPSP synthase

5-enolpyruvylshikimate-3-phosphate synthase3-phosphoshikimate 1-carboxyvinyltransferase5-enolpyruvylshikimate-3-phosphate
EPSPS inhibitors: Enolpyruvylshikimate 3-phosphate synthase enzyme (EPSPS) is used in the synthesis of the amino acids tryptophan, phenylalanine and tyrosine. They affect grasses and dicots alike. Glyphosate (Roundup) is a systemic EPSPS inhibitor inactivated by soil contact.
It is the biological target of the herbicide glyphosate, and a glyphosate-resistant version of this gene has been used in genetically modified crops.

Carotenoid

carotenoidscarotinoidketo-carotenoid
HPPD inhibitors inhibit 4-Hydroxyphenylpyruvate dioxygenase, which are involved in tyrosine breakdown. Tyrosine breakdown products are used by plants to make carotenoids, which protect chlorophyll in plants from being destroyed by sunlight. If this happens, the plants turn white due to complete loss of chlorophyll, and the plants die. Mesotrione and sulcotrione are herbicides in this class; a drug, nitisinone, was discovered in the course of developing this class of herbicides.
Ketoclomazone is derived from herbicides applied to soil and binds to DXP synthase.

Juda Hirsch Quastel

Juda Quastel
Independently, a team under Juda Hirsch Quastel, working at the Rothamsted Experimental Station made the same discovery.
Best known is the compound commonly labeled as 2,4-D, one of the first systemic or hormone herbicides, a class of chemicals responsible for triggering a worldwide revolution in agricultural output and still the most widely used weed-killer in the world.

Fertigation

chemigationdrip fertigation
On large areas, herbicides may also at times be applied aerially using helicopters or airplanes, or through irrigation systems (known as chemigation).
Chemigation often involves insecticides herbicides, and fungicides, some of which pose health threat to humans, animals, and the environment.

Organic farming

organicorganic agricultureorganic farm
The term organic herbicide has come to mean herbicides intended for organic farming.
Soil-bound organisms often benefit because of increased bacteria populations due to natural fertilizer such as manure, while experiencing reduced intake of herbicides and pesticides.

Perennial plant

perennialperennialsherbaceous perennial
This can successfully treat annual plants but not perennials.
Perennial plants often have deep, extensive root systems which can hold soil to prevent erosion, capture dissolved nitrogen before it can contaminate ground and surface water, and out-compete weeds (reducing the need for herbicides).

Agent White

The manufacturer of Tordon 101 (Dow AgroSciences, owned by the Dow Chemical Company) has claimed Tordon 101 has no effects on animals and insects, in spite of evidence of strong carcinogenic activity of the active ingredient Picloram in studies on rats.
Agent White is the code name for a herbicide used by the U.S. military in its herbicidal warfare program during the Vietnam War.

Sprayer

crop sprayerSprayhigh-pressure sprayers
Ground equipment varies in design, but large areas can be sprayed using self-propelled sprayers equipped with long booms, of 60 to 120 ft with spray nozzles spaced every 20-30 in apart.
In agriculture, a sprayer is a piece of equipment that is used to apply herbicides, pesticides, and fertilizers on agricultural crops.