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Bibliography Tag: resistant weeds

Liebman et al., 2016

Matt Liebman, Bàrbara Baraibar, Yvonne Buckley, Dylan Childs, Svend Christensen, Roger Cousens, Hanan Eizenberg, Sanne Heijting, Donato Loddo, Aldo Merotto Jr, Michael Renton, Marleen Riemens, “Ecologically sustainable weed management: How do we get from proof-of-concept to adoption?,” Ecological Applications, 26:5, 2016, DOI: 10.1002/15-0995


Weed management is a critically important activity on both agricultural and non‐agricultural lands, but it is faced with a daunting set of challenges: environmental damage caused by control practices, weed resistance to herbicides, accelerated rates of weed dispersal through global trade, and greater weed impacts due to changes in climate and land use. Broad‐scale use of new approaches is needed if weed management is to be successful in the coming era. We examine three approaches likely to prove useful for addressing current and future challenges from weeds: diversifying weed management strategies with multiple complementary tactics, developing crop genotypes for enhanced weed suppression, and tailoring management strategies to better accommodate variability in weed spatial distributions. In all three cases, proof‐of‐concept has long been demonstrated and considerable scientific innovations have been made, but uptake by farmers and land managers has been extremely limited. Impediments to employing these and other ecologically based approaches include inadequate or inappropriate government policy instruments, a lack of market mechanisms, and a paucity of social infrastructure with which to influence learning, decision‐making, and actions by farmers and land managers. We offer examples of how these impediments are being addressed in different parts of the world, but note that there is no clear formula for determining which sets of policies, market mechanisms, and educational activities will be effective in various locations. Implementing new approaches for weed management will require multidisciplinary teams comprised of scientists, engineers, economists, sociologists, educators, farmers, land managers, industry personnel, policy makers, and others willing to focus on weeds within whole farming systems and land management units. FULL TEXT

Liebman and Davis, 2009

Matt Liebman and Adam Davis, “Managing Weeds in Organic Farming Systems: An Ecological Approach,” In Organic Farming: The Ecological System, Ed: Charles Francis, 2009.


In this chapter, we describe major components of the weed management tool kit for organic farming, highlighting areas in which important advances have been made in the last decade. We then argue that instead of approaching the development of multitactic weed management strategies as a purely empirical, trial-and-error activity, the choice and deployment of weed management tactics should instead be informed by insights from ecological theory… Finally, we emphasize the need for ongoing dialog between empiricists and theoreticians and between scientists and farmers, so as to better direct scarce research resources and management time to where they are likely to be most beneficial. Multitactic weed management strategies informed by theory should be useful not just to organic farmers but also to conventional farmers who seek to reduce their reliance on herbicides due to concerns over herbicide resistance in weeds, rising production costs, and environmental and human health risks associated with herbicide exposure. FULL TEXT

Duke, 2015

Stephen O Duke, “Perspectives on transgenic, herbicide‐resistant crops in the United States almost 20 years after introduction,” Pest Management Science, 2015, 71:5, DOI: 10.1002/ps.3863.


Herbicide-resistant crops have had profound impacts on weed management. Most of the impact has been by glyphosate-resistant maize, cotton, soybean, and canola. Significant economic savings, yield increases, and more efficacious and simplified weed management resulted in widespread adoption of the technology. Initially, glyphosate-resistant crops enabled significantly reduced tillage and reduced the environmental impact of weed management. Continuous use of glyphosate with glyphosate-resistant crops over broad areas facilitated the evolution of glyphosate-resistant weeds, which have resulted in increases in the use of tillage and other herbicides with glyphosate, reducing some of the initial environmental benefits of glyphosate-resistant crops. Transgenic crops with resistance to auxinic herbicides, as well as to herbicides that inhibit acetolactate synthase, acetyl-CoA carboxylase, and hydroxyphenylpyruvate dioxygenase, stacked with glyphosate and/or glufosinate resistance, will become available in the next few years. These technologies will provide additional weed management options for farmers, but will not have all of the positive impacts (reduced cost, simplified weed management, lowered environmental impact, and reduced tillage) that glyphosate-resistant crops had initially. In the more distant future, other herbicide-resistant crops (including non-transgenic ones), herbicides with new modes of action, and technologies that are currently in their infancy (e.g., bioherbicides, sprayable herbicidal RNAi, and/or robotic weeding) may impact the role of transgenic, herbicide-resistant crops in weed management.

Schütte et al., 2017

Gesine Schütte, Michael Eckerstorfer, Valentina Rastelli, Wolfram Reichenbecher, Sara Restrepo‑Vassalli, Marja Ruohonen‑Lehto, Anne‑Gabrielle Wuest Saucy, and Martha Mertens, “Herbicide resistance and biodiversity: agronomic and environmental aspects of genetically modified herbicide-resistant plants,” Environmental Sciences Europe, 2017, 29:5, DOI: 10.1186/s12302-016-0100-y.


Farmland biodiversity is an important characteristic when assessing sustainability of agricultural practices and is of major international concern. Scientific data indicate that agricultural intensification and pesticide use are among the main drivers of biodiversity loss. The analysed data and experiences do not support statements that herbicide-resistant crops provide consistently better yields than conventional crops or reduce herbicide amounts. They rather show that the adoption of herbicide-resistant crops impacts agronomy, agricultural practice, and weed management and contributes to biodiversity loss in several ways: (i) many studies show that glyphosate-based herbicides, which were commonly regarded as less harmful, are toxic to a range of aquatic organisms and adversely affect the soil and intestinal microflora and plant disease resistance; the increased use of 2,4-D or dicamba, linked to new herbicide-resistant crops, causes special concerns. (ii) The adoption of herbicide-resistant crops has reduced crop rotation and favoured weed management that is solely based on the use of herbicides. (iii) Continuous herbicide resistance cropping and the intensive use of glyphosate over the last 20 years have led to the appearance of at least 34 glyphosate-resistant weed species worldwide. Although recommended for many years, farmers did not counter resistance development in weeds by integrated weed management, but continued to rely on herbicides as sole measure. Despite occurrence of widespread resistance in weeds to other herbicides, industry rather develops transgenic crops with additional herbicide resistance genes. (iv) Agricultural management based on broad-spectrum herbicides as in herbicide-resistant crops further decreases diversity and abundance of wild plants and impacts arthropod fauna and other farmland animals. Taken together, adverse impacts of herbicide-resistant crops on biodiversity, when widely adopted, should be expected and are indeed very hard to avoid. For that reason, and in order to comply with international agreements to protect and enhance biodiversity, agriculture needs to focus on practices that are more environmentally friendly, including an overall reduction in pesticide use. (Pesticides are used for agricultural as well non-agricultural purposes. Most commonly they are used as plant protection products and regarded as a synonym for it and so also in this text.) FULL TEXT

Londo et al., 2014

Jason Paul Londo, John McKinney, Matthew Schwartz, Mike Bollman, Cynthia Sagers, and Lidia Watrud, “Sub-lethal glyphosate exposure alters flowering phenology and causes transient male-sterility in Brassica spp,” BMC Plant Biology, 2014, 14:70.


BACKGROUND: Herbicide resistance in weedy plant populations can develop through different mechanisms such as gene flow of herbicide resistance transgenes from crop species into compatible weedy species or by natural evolution of herbicide resistance or tolerance following selection pressure. Results from our previous studies suggest that sub-lethal levels of the herbicide glyphosate can alter the pattern of gene flow between glyphosate resistant Canola®, Brassica napus, and glyphosate sensitive varieties of B. napus and B. rapa. The objectives of this study were to examine the phenological and developmental changes that occur in Brassica crop and weed species following sub-lethal doses of the herbicides glyphosate and glufosinate. We examined several vegetative and reproductive traits of potted plants under greenhouse conditions, treated with sub-lethal herbicide sprays.

RESULTS: Our results indicate that exposure of Brassica spp. to a sub-lethal dose of glyphosate results in altering flowering phenology and reproductive function. Flowering of all sensitive species was significantly delayed and reproductive function, specifically male fertility, was suppressed. Higher dosage levels typically contributed to an increase in the magnitude of phenotypic changes.

CONCLUSIONS: These results demonstrate that Brassica spp. plants that are exposed to sub-lethal doses of glyphosate could be subject to very different pollination patterns and an altered pattern of gene flow that would result from changes in the overlap of flowering phenology between species. Implications include the potential for increased glyphosate resistance evolution and spread in weedy communities exposed to sub-lethal glyphosate.  FULL TEXT

Johnson et. al, 2009

William G. Johnson, Vince M. Davis, Greg R. Kruger, Stephen C. Weller, “Influence of glyphosate-resistant cropping systems on weed species shifts and glyphosate-resistant weed populations,” European Journal of Agonomy, 2009, 31, 162-172, DOI: 10.1016/j.eja.2009.03.008.


Glyphosate-resistant (GR) crops have facilitated increases in conservation tillage production practices and simplified weed control in GR corn, soybean, canola and cotton. Increased reliance on glyphosate, many times as the only active ingredient used, has resulted in weed species shifts and the evolution of weed populations resistant to glyphosate. However, weed shifts and the evolution of herbicide resistance are not new in regard to glyphosate use. Similar effects have been documented to many other historically important weed control advancements for agricultural crop production. GR crop technology was developed to utilize glyphosate for postemergence weed control and industry scientists suggested that there was little fear of weed shifts and resistance evolution due to the broad spectrum of weeds controlled by glyphosate. However, over the last decade, the most problematic weeds in agronomic cropping systems have shifted away from perennial grass and perennial broadleaf weeds to primarily annual broadleaf weeds. The evolution of several GR annual broadleaf weeds in GR cropping systems has been documented, and glyphosate resistance mechanisms in weeds are currently poorly understood.  FULL TEXT

Kremer, 2014

Robert J. Kremer, “Environmental Implications of Herbicide Resistance: Soil Biology and Ecology,” Weed Science, 2014, 62.


Soil microbial community structure and activity are linked to plant communities. Weeds may alter their soil environment, selecting for specific rhizosphere microbial communities. Rhizosphere modification occurs for many crop and horticultural plants. However, impacts of weeds in agroecosystems on soil biology and ecology have received less attention because effective weed management practices were developed to minimize their impacts on crop production. The recent development of herbicide resistance (HR) in several economically important weeds leading to widespread infestations in crop fields treated with a single herbicide has prompted a re-evaluation of the effects of weed growth on soil biology and ecology. The objective of this article is to review the potential impacts of herbicide-resistant weeds on soil biological and ecological properties based on reports for crops, weeds, and invasive plants. Persistent weed infestations likely establish extensive root systems and release various plant metabolites through root exudation. Many exudates are selective for specific soil microbial groups mediating biochemical and nutrient acquisition processes. Exudates may stimulate development of microbial groups beneficial to weed but detrimental to crop growth or beneficial to both. Changes in symbiotic and associative microbial interactions occur, especially for arbuscular mycorrhizal fungi (AMF) that are important in plant uptake of nutrients and water, and protecting from phytopathogens. Mechanisms used by weeds to disrupt symbioses in crops are not clearly described. Many herbicide-resistant weeds including Amaranthus and Chenopodium do not support AMF symbioses, potentially reducing AMF propagule density and establishment with crop plants. Herbicides applied to control HR weeds may compound effects of weeds on soil microorganisms. Systemic herbicides released through weed roots may select microbial groups that mediate detrimental processes such as nutrient immobilization or serve as opportunistic pathogens. Understanding complex interactions of weeds with soil microorganisms under extensive infestations is important in developing effective management of herbicide-resistant weeds. FULL TEXT

Behrens et al., 2007

Mark Behrens, Nedim Mutlu, Sarbani Chakraborty, Razvan Dumitru, Wen Zhi Jiang, “Dicamba Resistance: Enlarging and Preserving Biotechnology-Based Weed Management Strategies,” Science, 316, 2007, DOI: 10.1126/science.1141596.


Abstract: The advent of biotechnology-derived, herbicide-resistant crops has revolutionized farming practices in many countries. Facile, highly effective, environmentally sound, and profitable weed control methods have been rapidly adopted by crop producers who value the benefits associated with biotechnology-derived weed management traits. But a rapid rise in the populations of several troublesome weeds that are tolerant or resistant to herbicides currently used in conjunction with herbicide-resistant crops may signify that the useful lifetime of these economically important weed management traits will be cut short. We describe the development of soybean and other broadleaf plant species resistant to dicamba, a widely used, inexpensive, and environmentally safe herbicide. The dicamba resistance technology will augment current herbicide resistance technologies and extend their effective lifetime. Attributes of both nuclear- and chloroplast-encoded dicamba resistance genes that affect the potency and expected durability of the herbicide resistance trait are  examined.  FULL TEXT

van Bruggen et al., 2018

Ariena H.C. van Bruggen, Max Teplitski, Volker Mai, Kwang Cheol Jeong, Joan D. Flocks, Maria R. Finckh, and J. Glenn Morris, Jr., “Environmental and health effects of the herbicide glyphosate,” 2018,  Science of the Total Environment, 2018, 616-617,  DOI: 10.1016/j.scitotenv.2017.10.309.


BACKGROUND: The WHO reclassified the herbicide glyphosate as probably carcinogenic to humans, and concerns about potential side effects of the large-scale use of glyphosate have increased. We are interested in potential indirect effects of glyphosate on animal, human and plant health due to shifts in microbial community composition and antibiotic resistance in soil, plant surfaces and intestinal tracts.

OBJECTIVES: We review the scientific literature on glyphosate use, its toxicity to macro- and microorganisms, effects on microbial compositions, and potential indirect effects on plant, animal and human health. We hypothesize that glyphosate use has increased antibiotic resistance and propose study designs for testing this hypothesis.

DISCUSSION: Although the acute toxic effects of glyphosate on mammals are low, the chronic effects on human and animal health could be considerable due to accumulation in the environment. Intensive glyphosate use has led to the selection of glyphosate-resistant weeds and microorganisms. Shifts in microbial compositions due to selective pressure by glyphosate may have contributed to the proliferation of pathogens. Research on a link between glyphosate and antibiotic resistance is scarce. We hypothesize that the selection pressure for glyphosate resistance in bacteria could lead to shifts in microbiome composition and increases in antibiotic resistance.

CONCLUSION: We recommend interdisciplinary research on the associations between glyphosate use, distortions in microbial communities, expansion of antibiotic resistance and the emergence of animal, human and plant diseases. Independent research is needed to revisit the tolerance thresholds for glyphosate residues in food and animal feed taking all possible health risks into account.  FULL TEXT

Purdue Extension, 2013

Purdue Extension, “Corn and Soybean Herbicide Chart,” 2013.


This chart groups herbicides by their modes of action to assist you in selecting herbicides 1) to maintain greater diversity in herbicide use and 2) to rotate among herbicides with different sites of action to delay the development of herbicide resistance.  FULL TEXT

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