Misplaced Pages

#973026

62-544: Lolium temulentum , typically known as darnel , poison darnel , darnel ryegrass or cockle , is an annual plant of the genus Lolium within the family Poaceae . The plant stem can grow up to one meter tall, with inflorescence in the ears and purple grain. It has a cosmopolitan distribution . Darnel usually grows in the same production zones as wheat and was a serious weed of cultivation until modern sorting machinery enabled darnel seeds to be separated efficiently from seed wheat. The similarity between these two plants

124-552: A 1995 panel of 13 scientists reviewing studies on the carcinogenicity of 2,4-D had divided opinions on the likelihood 2,4-D causes cancer in humans. As of 1992 , studies on phenoxy herbicides were too few to accurately assess the risk of many types of cancer from these herbicides, even although evidence was stronger that exposure to these herbicides is associated with increased risk of soft tissue sarcoma and non-Hodgkin lymphoma . Herbicides have widely variable toxicity in addition to acute toxicity arising from ingestion of

186-411: A dynamic system, rather than an inert substance, he was able to apply techniques such as perfusion . Quastel was able to quantify the influence of various plant hormones , inhibitors, and other chemicals on the activity of microorganisms in the soil and assess their direct impact on plant growth . While the full work of the unit remained secret, certain discoveries were developed for commercial use after

248-415: A few weeks) after being applied to soils of above-neutral pH . Under alkaline soil conditions, atrazine may be carried into the soil profile as far as the water table by soil water following rainfall causing the aforementioned contamination. Atrazine is thus said to have "carryover", a generally undesirable property for herbicides. Glyphosate had been first prepared in the 1950s but its herbicidal activity

310-568: A likely relationship to increased risk of breast cancer , although a causal relationship remains unclear. Herbicide manufacturers have at times made false or misleading claims about the safety of their products. Chemical manufacturer Monsanto Company agreed to change its advertising after pressure from New York attorney general Dennis Vacco ; Vacco complained about misleading claims that its spray-on glyphosate-based herbicides, including Roundup, were safer than table salt and "practically non-toxic" to mammals, birds, and fish (though proof that this

372-604: A molecular mode of action for which there is no resistance. Because most herbicides could not kill all weeds, farmers rotate crops and herbicides to stop the development of resistant weeds. A 2008–2009 survey of 144 populations of waterhemp in 41 Missouri counties revealed glyphosate resistance in 69%. Weeds from some 500 sites throughout Iowa in 2011 and 2012 revealed glyphosate resistance in approximately 64% of waterhemp samples. As of 2023, 58 weed species have developed glyphosate resistance. Weeds resistant to multiple herbicides with completely different biological action modes are on

434-483: A short period after application. Herbicides can be classified/grouped in various ways; for example, according to their activity, the timing of application, method of application, mechanism of their action, and their chemical structures. Chemical structure of the herbicide is of primary affecting efficacy. 2,4-D, mecoprop , and dicamba control many broadleaf weeds but remain ineffective against turf grasses. Chemical additives influence selectivity. Surfactants alter

496-442: A significant quantity rapidly, and chronic toxicity arising from environmental and occupational exposure over long periods. Much public suspicion of herbicides revolves around a confusion between valid statements of acute toxicity as opposed to equally valid statements of lack of chronic toxicity at the recommended levels of usage. For instance, while glyphosate formulations with tallowamine adjuvants are acutely toxic, their use

558-399: A single plant. In 2015, Monsanto released crop seed varieties resistant to both dicamba and glyphosate, allowing for use of a greater variety of herbicides on fields without harming the crops. By 2020, five years after the release of dicamba-resistant seed, the first example of dicamba-resistant Palmer amaranth was found in one location. When mutations occur in the genes responsible for

620-420: A wick wetted with herbicide is suspended from a boom and dragged or rolled across the tops of the taller weed plants. This allows treatment of taller grassland weeds by direct contact without affecting related but desirable shorter plants in the grassland sward beneath. The method has the benefit of avoiding spray drift. In Wales , a scheme offering free weed-wiper hire was launched in 2015 in an effort to reduce

682-613: A wide range of chemicals to achieve the same effect at lower cost and better efficacy, including 2,4-D. In the same year, R. Pokorny in the US achieved this as well. Independently, a team under Juda Hirsch Quastel , working at the Rothamsted Experimental Station made the same discovery. Quastel was tasked by the Agricultural Research Council (ARC) to discover methods for improving crop yield. By analyzing soil as

SECTION 10

#1732869368974

744-459: Is black. Darnel can be infected by an endophytic fungus of the genus Neotyphodium and the endophyte-produced, insecticidal loline alkaloids were first isolated from this plant. The French word for darnel is ivraie (from Latin ebriacus , intoxicated), which expresses the drunken nausea from eating the infected plant, which can be fatal. The French name echoes the scientific name, Latin temulentus "drunk." Let both grow together until

806-479: Is called allelopathy . The applicability of these agents is unclear. Herbicide resistance became a critical problem in Australian agriculture after many Australian sheep farmers began to exclusively grow wheat in their pastures in the 1970s. Introduced varieties of ryegrass , while good for grazing sheep, compete intensely with wheat. Ryegrasses produce so many seeds that, if left unchecked, they can completely choke

868-418: Is described as having low residual activity if it is neutralized within a short time of application (within a few weeks or months) – typically this is due to rainfall, or reactions in the soil. A herbicide described as having high residual activity will remain potent for the long term in the soil. For some compounds, the residual activity can leave the ground almost permanently barren. Herbicides interfere with

930-529: Is meant to provide end-users with guidance on managing pesticide resistance. An example of a fully executed label compliant with the USEPA resistance management labeling guidance can be seen on the specimen label for the herbicide, cloransulam-methyl, updated in 2022. Optimising herbicide input to the economic threshold level should avoid the unnecessary use of herbicides and reduce selection pressure. Herbicides should be used to their greatest potential by ensuring that

992-506: Is native to Europe , Asia and northern Africa , as well as being cultivated and naturalized in Australia , the Americas , and various oceanic islands. Ryegrasses are naturally diploid , with 2n=14, and are closely related to the fescues ( Festuca ). Ryegrass should not be confused with rye , which is a grain crop. As of February 2024 the species of Lolium listed by Plants of

1054-575: Is often attributed to overuse as well as the strong evolutionary pressure on the affected weeds. Three agricultural practices account for the evolutionary pressure upon weeds to evolve resistance: monoculture , neglecting non-herbicide weed control practices, and reliance on one herbicide for weed control. To minimize resistance, rotational programs of herbicide application, where herbicides with multiple modes of action are used, have been widely promoted. In particular, glyphosate resistance evolved rapidly in part because when glyphosate use first began, it

1116-426: Is so great that in some regions, darnel is referred to as " false wheat ". It bears a close resemblance to wheat until the ear appears. The spikes of L. temulentum are more slender than those of wheat. The spikelets are oriented edgeways to the rachis and have only a single glume , while those of wheat are oriented with the flat side to the rachis and have two glumes. Wheat will appear brown when ripe, whereas darnel

1178-569: Is the principal grazing grass in New Zealand where some 10 million kilograms of certified seed are produced every year. There is a large range of cultivars . The primary species found worldwide and used both for lawns and as a forage crop is perennial ryegrass ( Lolium perenne ). Like many cool-season grasses of the Poaceae, it harbors a symbiotic fungal endophyte , either Epichloë or its close relative Neotyphodium , both of which are members of

1240-574: The All England Lawn Tennis and Croquet Club , the venue for Wimbledon , are planted with ryegrass. Glyphosate -resistant Lolium has been reported from Mississippi in 2006. Herbicide resistance In the United States in 2012, about 91% of all herbicide usage, determined by weight applied, was in agriculture. In 2012, world pesticide expenditures totaled nearly $ 24.7 billion; herbicides were about 44% of those sales and constituted

1302-498: The Viet Nam Red Cross Society estimates that up to one million people were disabled or have health problems as a result of exposure to Agent Orange. The United States government has described these figures as unreliable. In general, many questions exist about the health and environmental effects of many herbicides because of the large number of herbicides and the myriad potential targets, mostly unintended. For example,

SECTION 20

#1732869368974

1364-606: The Vietnam War has left tangible, long-term impacts upon the Vietnamese people and U.S soldiers that handled the chemicals. More than 20% of South Vietnam's forests and 3.2% of its cultivated land were sprayed at least once between during the war. The government of Vietnam says that up to four million people in Vietnam were exposed to the defoliant, and as many as three million people have suffered illness because of Agent Orange, while

1426-480: The UK has been linked to a decline in seed-eating bird species which rely on the weeds killed by the herbicides. Heavy use of herbicides in neotropical agricultural areas has been one of many factors implicated in limiting the usefulness of such agricultural land for wintering migratory birds. One major complication to the use of herbicides for weed control is the ability of plants to evolve herbicide resistance , rendering

1488-642: The United Kingdom and the United States into the potential use of herbicides in war . The compound 2,4-D was first synthesized by W. G. Templeman at Imperial Chemical Industries . In 1940, his work with indoleacetic acid and naphthaleneacetic acid indicated that "growth substances applied appropriately would kill certain broad-leaved weeds in cereals without harming the crops," though these substances were too expensive and too short-lived in soil due to degradation by microorganisms to be of practical agricultural use; by 1941, his team succeeded in synthesizing

1550-1354: The Weed Science Society of America (WSSA) and herbicide Resistance and World Grains (HRAC) systems, herbicides are classified by mode of action. Eventually the Herbicide Resistance Action Committee (HRAC) and the Weed Science Society of America (WSSA) developed a classification system. Groups in the WSSA and the HRAC systems are designated by numbers and letters, inform users awareness of herbicide mode of action and provide more accurate recommendations for resistance management. Most herbicides are applied as water-based sprays using ground equipment. Ground equipment varies in design, but large areas can be sprayed using self-propelled sprayers equipped with long booms, of 60 to 120 feet (18 to 37 m) with spray nozzles spaced every 20–30 inches (510–760 mm) apart. Towed, handheld, and even horse-drawn sprayers are also used. On large areas, herbicides may also at times be applied aerially using helicopters or airplanes, or through irrigation systems (known as chemigation ). Weed-wiping may also be used, where

1612-501: The World Online include: Several former Lolium species now regarded as part of other genera: Castellia , Enteropogon , × Festulolium , Hainardia , Lepturus , Melica , and Vulpia . Lolium contains some species which are important grasses for lawns , and as pasture and for grazing and hay for livestock , being a highly nutritious stock feed. Ryegrasses are also used in soil erosion control programs. It

1674-545: The active ingredient, picloram , in studies on rats. Herbicide use generally has negative impacts on many aspects of the environment. Insects, non-targeted plants, animals, and aquatic systems subject to serious damage from herbicides. Impacts are highly variable. Atrazine has often been blamed for affecting reproductive behavior of aquatic life, but the data do not support this assertion. Bird populations are one of many indicators of herbicide damage.Most observed effects are due not to toxicity, but to habitat changes and

1736-456: The badly infested areas of fields, is another means of reducing total herbicide use. When resistance is first suspected or confirmed, the efficacy of alternatives is likely to be the first consideration. If there is resistance to a single group of herbicides, then the use of herbicides from other groups may provide a simple and effective solution, at least in the short term. For example, many triazine-resistant weeds have been readily controlled by

1798-512: The biggest portion, followed by insecticides , fungicides , and fumigants . Herbicide is also used in forestry, where certain formulations have been found to suppress hardwood varieties in favor of conifers after clearcutting , as well as pasture systems. Prior to the widespread use of herbicides, cultural controls , such as altering soil pH , salinity, or fertility levels, were used to control weeds. Mechanical control including tillage and flooding were also used to control weeds. In

1860-409: The biochemical machinery that supports plant growth. Herbicides often mimic natural plant hormones , enzyme substrates, and cofactors . They interfere with the metabolism in the target plants. Herbicides are often classified according to their site of action because as a general rule, herbicides within the same site of action class produce similar symptoms on susceptible plants. Classification based on

1922-470: The biological mechanisms that herbicides interfere with, these mutations may cause the herbicide mode of action to work less effectively. This is called target-site resistance. Specific mutations that have the most helpful effect for the plant have been shown to occur in separate instances and dominate throughout resistant weed populations. This is an example of convergent evolution . Some mutations conferring herbicide resistance may have fitness costs, reducing

Lolium temulentum - Misplaced Pages Continue

1984-402: The decreases in abundance of species on which birds rely for food or shelter. Herbicide use in silviculture , used to favor certain types of growth following clearcutting , can cause significant drops in bird populations. Even when herbicides which have low toxicity to birds are used, they decrease the abundance of many types of vegetation on which the birds rely. Herbicide use in agriculture in

2046-586: The effectiveness of combining herbicides is also questioned, particularly in light of the rise of non-target site resistance. Plants developed resistance to atrazine and to ALS-inhibitors relatively early, but more recently, glyphosate resistance has dramatically risen. Marestail is one weed that has developed glyphosate resistance. Glyphosate-resistant weeds are present in the vast majority of soybean, cotton and corn farms in some U.S. states. Weeds that can resist multiple other herbicides are spreading. Few new herbicides are near commercialization, and none with

2108-472: The first application. If these are resistant, then the second herbicide in the sequence may increase selection for resistant individuals by killing the susceptible plants which were damaged but not killed by the first application, but allowing the larger, less affected, resistant plants to survive. This has been cited as one reason why ALS-resistant Stellaria media has evolved in Scotland recently (2000), despite

2170-677: The following biochemical mechanisms: The following terms are also used to describe cases where plants are resistant to multiple herbicides at once: Due to herbicide resistance – a major concern in agriculture – a number of products combine herbicides with different means of action. Integrated pest management may use herbicides alongside other pest control methods. Integrated weed management (IWM) approach utilizes several tactics to combat weeds and forestall resistance. This approach relies less on herbicides and so selection pressure should be reduced. By relying on diverse weed control methods, including non-herbicide methods of weed control,

2232-456: The following commercial products cycloxydim , clethodim , tralkoxydim , butroxydim , sethoxydim , profoxydim , and mesotrione . Knowing about herbicide chemical family grouping serves as a short-term strategy for managing resistance to site of action. The phenoxyacetic acid mimic the natural auxin indoleacetic acid (IAA). This family includes MCPA , 2,4-D , and 2,4,5-T , picloram , dicamba , clopyralid , and triclopyr . Using

2294-442: The fungal family Clavicipitaceae . Some species, particularly L. temulentum , are weeds which can have a severe impact on the production of wheat and other crops. Annual ryegrass ( L. rigidum ) is one of the most serious and costly weeds of cropping systems in southern Australia, and herbicide resistance is a frequent problem. Ryegrass pollen is also one of the major causes of hay fever . Tennis courts , including those at

2356-446: The harvest: and in the time of harvest I will say to the reapers, Gather ye together first the tares , and bind them in bundles to burn them: but gather the wheat into my barn. Lolium Lolium is a genus of tufted grasses in the bluegrass subfamily (Pooideae). It is often called ryegrass, but this term is sometimes used to refer to grasses in other genera. They are characterized by bunch-like growth habits. Lolium

2418-497: The herbicide coming into direct contact with people or wildlife, inhalation of aerial sprays, or food consumption prior to the labelled preharvest interval. Under some conditions, certain herbicides can be transported via leaching or surface runoff to contaminate groundwater or distant surface water sources. Generally, the conditions that promote herbicide transport include intense storm events (particularly shortly after application) and soils with limited capacity to adsorb or retain

2480-460: The herbicides ineffective against target plants. Out of 31 known herbicide modes of action, weeds have evolved resistance to 21. 268 plant species are known to have evolved herbicide resistance at least once. Herbicide resistance was first observed in 1957, and since has evolved repeatedly in weed species from 30 families across the globe. Weed resistance to herbicides has become a major concern in crop production worldwide. Resistance to herbicides

2542-428: The herbicides. Herbicide properties that increase likelihood of transport include persistence (resistance to degradation) and high water solubility. Cases have been reported where Phenoxy herbicides are contaminated with dioxins such as TCDD ; research has suggested such contamination results in a small rise in cancer risk after occupational exposure to these herbicides. Triazine exposure has been implicated in

Lolium temulentum - Misplaced Pages Continue

2604-457: The jungle. Deployment of herbicides and defoliants served the dual purpose of thinning jungle trails to prevent ambushes and destroying crop fields in regions where the MNLA was active to deprive them of potential sources of food. As part of this process, herbicides and defoliants were also sprayed from Royal Air Force aircraft. The use of herbicides as a chemical weapon by the U.S. military during

2666-466: The late 19th and early 20th centuries, inorganic chemicals such as sulfuric acid , arsenic, copper salts, kerosene and sodium chlorate were used to control weeds, but these chemicals were either toxic, flammable or corrosive and were expensive and ineffective at controlling weeds. The major breakthroughs occurred during the Second World War as the result of research conducted independently in

2728-823: The leaf more readily at high humidity by lengthening the drying time of the spray droplet and increasing cuticle hydration. Light of high intensity may break down some herbicides and cause the leaf cuticle to thicken, which can interfere with absorption. Precipitation may wash away or remove some foliage-applied herbicides, but it will increase root absorption of soil-applied herbicides. Drought-stressed plants are less likely to translocate herbicides. As temperature increases, herbicides' performance may decrease. Absorption and translocation may be reduced in very cold weather. Non-selective herbicides, generally known as defoliants , are used to clear industrial sites, waste grounds, railways, and railway embankments. Paraquat , glufosinate , and glyphosate are non-selective herbicides. An herbicide

2790-560: The levels of MCPA in water courses. There is little difference in forestry in the early growth stages, when the height similarities between growing trees and growing annual crops yields a similar problem with weed competition. Unlike with annuals however, application is mostly unnecessary thereafter and is thus mostly used to decrease the delay between productive economic cycles of lumber crops. Herbicide volatilisation or spray drift may result in herbicide affecting neighboring fields or plants, particularly in windy conditions. Sometimes,

2852-410: The longer term. One practical advantage of sequences of two herbicides compared with mixtures is that a better appraisal of the efficacy of each herbicide component is possible, provided that sufficient time elapses between each application. A disadvantage with sequences is that two separate applications have to be made and it is possible that the later application will be less effective on weeds surviving

2914-456: The most commonly used herbicides in the world. Like other acid herbicides, current formulations use either an amine salt (often trimethylamine ) or one of many esters of the parent compound. The triazine family of herbicides, which includes atrazine , was introduced in the 1950s; they have the current distinction of being the herbicide family of greatest concern regarding groundwater contamination . Atrazine does not break down readily (within

2976-469: The physical properties of the spray solution and the overall phytotoxicity of the herbicide, increasing translocation. Herbicide safeners enhance the selectivity by boosting herbicide resistance by the crop but allowing the herbicide to damage the weed. Selectivity is determined by the circumstances and technique of application. Climatic factors affect absorption including humidity , light, precipitation, and temperature. Foliage-applied herbicides will enter

3038-580: The plant's ability to survive in other ways, but over time, the least costly mutations tend to dominate in weed populations. Recently, incidences of non-target site resistance have increasingly emerged, such as examples where plants are capable of producing enzymes that neutralize herbicides before they can enter the plant's cells – metabolic resistance . This form of resistance is particularly challenging, since plants can develop non-target-site resistance to herbicides their ancestors were never directly exposed to. Resistance to herbicides can be based on one of

3100-447: The regular use of a sequence incorporating mecoprop , a herbicide with a different mode of action. The term organic herbicide has come to mean herbicides intended for organic farming . Few natural herbicides rival the effectiveness of synthetics. Some plants also produce their own herbicides, such as the genus Juglans ( walnuts ), or the tree of heaven ; such actions of natural herbicides, and other related chemical interactions,

3162-424: The rise. In Missouri, 43% of waterhemp samples were resistant to two different herbicides; 6% resisted three; and 0.5% resisted four. In Iowa 89% of waterhemp samples resist two or more herbicides, 25% resist three, and 10% resist five. As of 2023, Palmer amaranth with resistance to six different herbicide modes of action has emerged. Annual bluegrass collected from a golf course in the U.S. state of Tennessee

SECTION 50

#1732869368974

3224-433: The selection pressure on weeds to evolve resistance can be lowered. Researchers warn that if herbicide resistance is combatted only with more herbicides, "evolution will most likely win." In 2017, the USEPA issued a revised Pesticide Registration Notice (PRN 2017-1), which provides guidance to pesticide registrants on required pesticide resistance management labeling. This requirement applies to all conventional pesticides and

3286-661: The site of action of the herbicide is preferable as herbicide resistance management can be handled more effectively. Classification by mechanism of action (MOA) indicates the first enzyme, protein, or biochemical step affected in the plant following application: Complementary to mechanism-based classifications, herbicides are often classified according to their chemical structures or motifs. Similar structural types work in similar ways. For example, aryloxphenoxypropionates herbicides ( diclofop chlorazifop , fluazifop ) appear to all act as ACCase inhibitors. The so-called cyclohexanedione herbicides, which are used against grasses, include

3348-416: The timing, dose, application method, soil and climatic conditions are optimal for good activity. In the UK, partially resistant grass weeds such as Alopecurus myosuroides (blackgrass) and Avena genus (wild oat) can often be controlled adequately when herbicides are applied at the 2-3 leaf stage, whereas later applications at the 2-3 tiller stage can fail badly. Patch spraying, or applying herbicide to only

3410-414: The use of alternative herbicides such as dicamba or glyphosate. The use of two or more herbicides which have differing modes of action can reduce the selection for resistant genotypes. Ideally, each component in a mixture should: No mixture is likely to have all these attributes, but the first two listed are the most important. There is a risk that mixtures will select for resistance to both components in

3472-471: The war, including the 2,4-D compound. When 2,4-D was commercially released in 1946, it became the first successful selective herbicide, triggering a worldwide revolution in agricultural output. 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). The low cost of 2,4-D has led to continued usage today, and it remains one of

3534-615: The wrong field or plants may be sprayed due to error. Although herbicidal warfare uses chemical substances , its main purpose is to disrupt agricultural food production or to destroy plants which provide cover or concealment to the enemy. During the Malayan Emergency , British Commonwealth forces deployed herbicides and defoliants in the Malaysian countryside in order to deprive Malayan National Liberation Army (MNLA) insurgents of cover, potential sources of food and to flush them out of

3596-399: Was continuously and heavily relied upon for weed control. This caused incredibly strong selective pressure upon weeds, encouraging mutations conferring glyphosate resistance to persist and spread. However, in 2015, an expansive study showed an increase in herbicide resistance as a result of rotation, and instead recommended mixing multiple herbicides for simultaneous application. As of 2023,

3658-517: Was ever said is hard to find). Roundup is toxic and has resulted in death after being ingested in quantities ranging from 85 to 200 ml, although it has also been ingested in quantities as large as 500 ml with only mild or moderate symptoms. 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

3720-454: Was found in 2020 to be resistant to seven herbicides at once. Rigid ryegrass and annual bluegrass share the distinction of the species with confirmed resistance to the largest number of herbicide modes of action, both with confirmed resistance to 12 different modes of action; however, this number references how many forms of herbicide resistance are known to have emerged in the species at some point, not how many have been found simultaneously in

3782-483: Was found to be uncorrelated with any health issues like cancer in a massive US Department of Health study on 90,000 members of farmer families for over a period of 23 years. That is, the study shows lack of chronic toxicity, but cannot question the herbicide's acute toxicity. Some herbicides cause a range of health effects ranging from skin rashes to death. The pathway of attack can arise from intentional or unintentional direct consumption, improper application resulting in

SECTION 60

#1732869368974

3844-448: Was only recognized in the 1960s. It was marketed as Roundup in 1971. The development of glyphosate-resistant crop plants, it is now used very extensively for selective weed control in growing crops. The pairing of the herbicide with the resistant seed contributed to the consolidation of the seed and chemistry industry in the late 1990s. Many modern herbicides used in agriculture and gardening are specifically formulated to degrade within

#973026