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Journal ArticleDOI

The current status and environmental impacts of glyphosate-resistant crops: a review.

01 Sep 2006-Journal of Environmental Quality (John Wiley & Sons, Ltd)-Vol. 35, Iss: 5, pp 1633-1658
TL;DR: Glyphosate-resistant crops have promoted the adoption of reduced- or no-tillage agriculture in the USA and Argentina, providing a substantial environmental benefit and the development and use of failsafe introgression barriers in crops with such linked genes is needed.
Abstract: Glyphosate [N-(phosphonomethyl) glycine]-resistant crops (GRCs), canola (Brassica napus L.), cotton (Gossypium hirsutum L.), maize (Zea mays L.), and soybean [Glycine max (L.) Merr.] have been commercialized and grown extensively in the Western Hemisphere and, to a lesser extent, elsewhere. Glyphosate-resistant cotton and soybean have become dominant in those countries where their planting is permitted. Effects of glyphosate on contamination of soil, water, and air are minimal, compared to some of the herbicides that they replace. No risks have been found with food or feed safety or nutritional value in products from currently available GRCs. Glyphosate-resistant crops have promoted the adoption of reduced- or no-tillage agriculture in the USA and Argentina, providing a substantial environmental benefit. Weed species in GRC fields have shifted to those that can more successfully withstand glyphosate and to those that avoid the time of its application. Three weed species have evolved resistance to glyphosate in GRCs. Glyphosate-resistant crops have greater potential to become problems as volunteer crops than do conventional crops. Glyphosate resistance transgenes have been found in fields of canola that are supposed to be non-transgenic. Under some circumstances, the largest risk of GRCs may be transgene flow (introgression) from GRCs to related species that might become problems in natural ecosystems. Glyphosate resistance transgenes themselves are highly unlikely to be a risk in wild plant populations, but when linked to transgenes that may impart fitness benefits outside of agriculture (e.g., insect resistance), natural ecosystems could be affected. The development and use of failsafe introgression barriers in crops with such linked genes is needed.

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Citations
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Journal ArticleDOI
TL;DR: The use of this virtually ideal herbicide is now being threatened by the evolution of glyphosate-resistant weeds, and adoption of resistance management practices will be required to maintain the benefits of glyphosate technologies for future generations.
Abstract: Since its commercial introduction in 1974, glyphosate [N-(phosphonomethyl)glycine] has become the dominant herbicide worldwide. There are several reasons for its success. Glyphosate is a highly effective broad-spectrum herbicide, yet it is very toxicologically and environmentally safe. Glyphosate translocates well, and its action is slow enough to take advantage of this. Glyphosate is the only herbicide that targets 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS), so there are no competing herbicide analogs or classes. Since glyphosate became a generic compound, its cost has dropped dramatically. Perhaps the most important aspect of the success of glyphosate has been the introduction of transgenic, glyphosate-resistant crops in 1996. Almost 90% of all transgenic crops grown worldwide are glyphosate resistant, and the adoption of these crops is increasing at a steady pace. Glyphosate/glyphosate-resistant crop weed management offers significant environmental and other benefits over the technologies that it replaces. The use of this virtually ideal herbicide is now being threatened by the evolution of glyphosate-resistant weeds. Adoption of resistance management practices will be required to maintain the benefits of glyphosate technologies for future generations. Copyright © 2008 Society of Chemical Industry

1,331 citations

Journal ArticleDOI
TL;DR: Glyphosate-resistant weeds are a major risk for the continued success of glyphosate and transgenic glyphosate-resistant crops, however, lessons can be learnt and actions taken to achieve glyphosate sustainability.
Abstract: Glyphosate is the world's most important herbicide, with many uses that deliver effective and sustained control of a wide spectrum of unwanted (weedy) plant species. Until recently there were relatively few reports of weedy plant species evolving resistance to glyphosate. Since 1996, the advent and subsequent high adoption of transgenic glyphosate-resistant crops in the Americas has meant unprecedented and often exclusive use of glyphosate forweedcontroloververylarge areas.Consequently, in regionsoftheUSA wheretransgenic glyphosate- resistant crops dominate, there are now evolved glyphosate-resistant populations of the economically damaging weed species Ambrosia artemissifolia L., Ambrosia trifida L., Amaranthus palmeri SW atson,Amaranthus rudis JD Sauer, Amaranthus tuberculatus (Moq) JD Sauer and various Conyza and Lolium spp. Likewise, in areas of transgenic glyphosate-resistant crops in Argentina and Brazil, there are now evolved glyphosate-resistant populations ofSorghum halepense (L.) Pers andEuphorbia heterophylla L. respectively. As transgenic glyphosate- resistant crops will remain very popular with producers, it is anticipated that glyphosate-resistant biotypes of other prominent weed species will evolve over the next few years. Therefore, evolved glyphosate-resistant weeds are a major risk for the continued success of glyphosate and transgenic glyphosate-resistant crops. However, glyphosate-resistant weeds are not yet a problem in many parts of the world, and lessons can be learnt and actions taken to achieve glyphosate sustainability. A major lesson is that maintenance of diversity in weed management systems is crucial for glyphosate to be sustainable. Glyphosate is essential for present and future world food production, and action to secure its sustainability for future gene rations is ag lobal imperative.  2008 Society of Chemical Industry

490 citations

Journal ArticleDOI
TL;DR: The economic stimulus to the herbicide industry caused by the evolution of herbicide-resistant weeds, especially GR weeds, may result in one or more new modes of action becoming available in the not too distant future.
Abstract: Herbicides with new modes of action are badly needed to manage the evolution of resistance of weeds to existing herbicides. Yet no major new mode of action has been introduced to the market place for about 20 years. There are probably several reasons for this. New potential products may have remained dormant owing to concerns that glyphosate-resistant (GR) crops have reduced the market for a new herbicide. The capture of a large fraction of the herbicide market by glyphosate with GR crops led to significantly diminished herbicide discovery efforts. Some of the reduced herbicide discovery research was also due to company consolidations and the availability of more generic herbicides. Another problem might be that the best herbicide molecular target sites may have already been discovered. However, target sites that are not utilized, for which there are inhibitors that are highly effective at killing plants, suggests that this is not true. Results of modern methods of target site discovery (e.g. gene knockout methods) are mostly not public, but there is no evidence of good herbicides with new target sites coming from these approaches. In summary, there are several reasons for a long dry period for new herbicide target sites; however, the relative magnitude of each is unclear. The economic stimulus to the herbicide industry caused by the evolution of herbicide-resistant weeds, especially GR weeds, may result in one or more new modes of action becoming available in the not too distant future. Copyright © 2011 Society of Chemical Industry

446 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive assessment of the environmental occurrence of glyphosate and aminomethylphosphonic acid (AMPA) in the United States conducted to date, summarizing the results of 3,732 water and sediment and 1,018 quality assurance samples collected between 2001 and 2010 from 38 states.
Abstract: Glyphosate use in the United States increased from less than 5,000 to more than 80,000 metric tons/yr between 1987 and 2007. Glyphosate is popular due to its ease of use on soybean, cotton, and corn crops that are genetically modified to tolerate it, utility in no-till farming practices, utility in urban areas, and the perception that it has low toxicity and little mobility in the environment. This compilation is the largest and most comprehensive assessment of the environmental occurrence of glyphosate and aminomethylphosphonic acid (AMPA) in the United States conducted to date, summarizing the results of 3,732 water and sediment and 1,018 quality assurance samples collected between 2001 and 2010 from 38 states. Results indicate that glyphosate and AMPA are usually detected together, mobile, and occur widely in the environment. Glyphosate was detected without AMPA in only 2.3% of samples, whereas AMPA was detected without glyphosate in 17.9% of samples. Glyphosate and AMPA were detected frequently in soils and sediment, ditches and drains, precipitation, rivers, and streams; and less frequently in lakes, ponds, and wetlands; soil water; and groundwater. Concentrations of glyphosate were below the levels of concern for humans or wildlife; however, pesticides are often detected in mixtures. Ecosystem effects of chronic low-level exposures to pesticide mixtures are uncertain. The environmental health risk of low-level detections of glyphosate, AMPA, and associated adjuvants and mixtures remain to be determined.

388 citations


Cites background from "The current status and environmenta..."

  • ...…“unlikely to leach into groundwater” due to their strong adsorptive characteristics (U.S. Environmental Protection Agency, 1993; Giesy et al., 2000; Cerdeira and Duke, 2006; Borggaard and Gimsing, 2008), at least one (Vereecken, 2005) suggested some potential for movement after heavy rainfall in…...

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  • ...DOI: 10.1111/jawr.12159...

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  • ...The majority of this increase is the result of glyphosate use on soybean, cotton, canola, and corn crops that have been genetically modified to tolerate this glyphosate (e.g., Roundup Ready crops) (Cerdeira and Duke, 2006; Young, 2006)....

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Journal ArticleDOI
TL;DR: This review is designed to update previous reviews of glyphosate‐based herbicide toxicity, with a focus on recent studies of the aquatic toxicity of this class of chemicals.
Abstract: Glyphosate [N-(phosphonomethyl) glycine] is a broad spectrum, post emergent herbicide and is among the most widely used agricultural chemicals globally. Initially developed to control the growth of weed species in agriculture, this herbicide also plays an important role in both modern silviculture and domestic weed control. The creation of glyphosate tolerant crop species has significantly increased the demand and use of this herbicide and has also increased the risk of exposure to non-target species. Commercially available glyphosate-based herbicides are comprised of multiple, often proprietary, constituents, each with a unique level of toxicity. Surfactants used to increase herbicide efficacy have been identified in some studies as the chemicals responsible for toxicity of glyphosate-based herbicides to non-target species, yet they are often difficult to chemically identify. Most glyphosate-based herbicides are not approved for use in the aquatic environment; however, measurable quantities of the active ingredient and surfactants are detected in surface waters, giving them the potential to alter the physiology of aquatic organisms. Acute toxicity is highly species dependant across all taxa, with toxicity depending on the timing, magnitude, and route of exposure. The toxicity of glyphosate to amphibians has been a major focus of recent research, which has suggested increased sensitivity compared with other vertebrates due to their life history traits and reliance on both the aquatic and terrestrial environments. This review is designed to update previous reviews of glyphosate-based herbicide toxicity, with a focus on recent studies of the aquatic toxicity of this class of chemicals.

359 citations

References
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01 Jan 1997

3,230 citations


"The current status and environmenta..." refers background in this paper

  • ...However, since this publication, several weed species have evolved resistance to glyphosate (Heap et al., 2005; Nandula et al., 2005) (Table 5), apparently through several different mechanisms....

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  • ...Although there are hundreds of cases of evolved resistance of weeds in fields of non-transgenic crops (Heap et al., 2005), there are no proven cases of introgression of herbicide resistance gene(s) from a naturally-resistant crop to an associated weed....

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  • ...Weed species that have evolved resistance to glyphosate (Heap et al., 2005)....

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  • ...An excellent web site exists that catalogs all verified cases of evolved resistance to herbicides (Heap et al., 2005)....

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Journal ArticleDOI
TL;DR: Under conservation tillage, a richer soil biota develops that can improve nutrient recycling and this may also help combat crop pests and diseases, and the greater availability of crop residues and weed seeds improves food supplies for insects, birds and small mammals.

965 citations


"The current status and environmenta..." refers background in this paper

  • ...A positive impact of the use of GRCs is that they facilitate reduced- or zero-tillage systems, which contribute to reductions in soil erosion from water and wind, fossil fuel use, air pollution from dust, loss of soil moisture, and soil compaction (Holland, 2004)....

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Book ChapterDOI
TL;DR: This work has compiled the most complete collection of these properties available, using others' compilations but verifying values from the primary literature in many cases, and suggests a "Selected Value" which it believes to be the best available.
Abstract: A principal goal of pesticide science is to be able to predict the environmental impact of a pesticide before it is released into the environment. To save expense and time, we would like to be able to make such a prediction for each pesticide with as few laboratory experiments on the pesticide as possible, and even fewer field experiments. Environmental processes, however, are enormously complex and sometimes (apparently) random. The sites of most interest—agricultural fields, forests, lakes, streams, etc.—are subtle living ecosystems which are incompletely understood and subject to great variability in space and time. The very diversity and intricacy which are indicators of the health of such ecosystems makes even the definition of what constitutes a significant impact on such systems a difficult task.

960 citations


"The current status and environmenta..." refers background in this paper

  • ...Glyphosate has a moderate half-life in soils with an avg value of approximately 47 d, but reaching 174 d in some soils under some conditions (Vencill, 2002; Wauchope et al., 1992)....

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Journal ArticleDOI
TL;DR: It was concluded that the use of Roundup herbicide does not result in adverse effects on development, reproduction, or endocrine systems in humans and other mammals, and glyphosate is noncarcinogenic.

742 citations

Journal ArticleDOI
TL;DR: This study represents one of the most extensive experimental inves- tigations of pesticide effects on aquatic communities and offers a comprehensive perspective on the impacts of pesticides when nontarget organisms are examined under ecologically relevant conditions.
Abstract: Pesticides constitute a major anthropogenic addition to natural communities. In aquatic communities, a great majority of pesticide impacts are determined from single- species experiments conducted under laboratory conditions. Although this is an essential protocol to rapidly identify the direct impacts of pesticides on organisms, it prevents an assessment of direct and indirect pesticide effects on organisms embedded in their natural ecological contexts. In this study, I examined the impact of four globally common pesticides (two insecticides, carbaryl (Sevin) and malathion; two herbicides, glyphosate (Roundup) and 2,4-D) on the biodiversity of aquatic communities containing algae and 25 species of animals. Species richness was reduced by 15% with Sevin, 30% with malathion, and 22% with Roundup, whereas 2,4-D had no effect. Both insecticides reduced zooplankton diversity by eliminating cladocerans but not copepods (the latter increased in abundance). The in- secticides also reduced the diversity and biomass of predatory insects and had an apparent indirect positive effect on several species of tadpoles, but had no effect on snails. The two herbicides had no effects on zooplankton, insect predators, or snails. Moreover, the herbicide 2,4-D had no effect on tadpoles. However, Roundup completely eliminated two species of tadpoles and nearly exterminated a third species, resulting in a 70% decline in the species richness of tadpoles. This study represents one of the most extensive experimental inves- tigations of pesticide effects on aquatic communities and offers a comprehensive perspective on the impacts of pesticides when nontarget organisms are examined under ecologically relevant conditions.

693 citations


"The current status and environmenta..." refers background in this paper

  • ...We discussed earlier that glyphosate formulations can be toxic to some amphibians when sprayed directly on them (Relyea, 2005)....

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  • ...Relyea (2005) reported that a commercial formulation of glyphosate sprayed directly into aquatic mesocosms (in 1200-...

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