Bibliography Tag: weed management systems

Bibliography Index

Westerman et al., 2005

Paula R. Westerman, Matt Liebman, Fabián D. Menalled, Andrew H. Heggenstaller, Robert G. Hartzler, Philip M. Dixon, “Are many little hammers effective? Velvetleaf (Abutilon theophrasti) population dynamics in two- and four-year crop rotation systems,” Weed Science, 53, 2005.

ABSTRACT:

To improve understanding of relationships between crop diversity, weed management practices, and weed population dynamics, we used data from a field experiment and matrix models to examine how contrasting crop rotations affect velvetleaf. We compared a 2-yr rotation system (corn-soybean) managed with conventional rates of herbicides with a 4-yr rotation (corn-soybean-triticale + alfalfa-alfalfa) that received 82% less herbicide. In November 2002, a pulse of velvetleaf seeds (500 seeds m⁻²) was added to 7- by 7-m areas within replicate plots of each crop phase-rotation system combination. Velvetleaf seed, seedling, and reproductive adult population densities, seed production, and seed losses to predators were measured during the next year. Velvetleaf seed production was greater in the 4-yr rotation than in the 2-yr rotation (460 vs. 16 seeds m⁻²). Averaged over 12 sampling periods from late May to mid-November 2003, loss of velvetleaf seeds to predators also was greater in the 4-yr rotation than in the 2-yr rotation (32 vs. 17% per 2 d). Modeling analyses indicated that velvetleaf density in the 4-yr rotation should decline if cumulative losses of seeds produced in the soybean phase exceeded 40%. Achieving such a level of predation appears possible, given the observed rates of velvetleaf seed predation. In addition, no tillage occurs in the 4-yr rotation for 26 mo after soybean harvest, thus favoring seed exposure on the soil surface to predators. Models that included estimates of seed predation indicated that to prevent increases in velvetleaf density, weed control efficacy in soybean must be ≥ 93% in the 2-yr rotation, but could drop to 86% in the 4-yr rotation. These results support the hypothesis that diverse rotations that exploit multiple stress and mortality factors, including weed seed predation, can contribute to effective weed suppression with less reliance on herbicides. FULL TEXT

Liebman, 2017

Matt Liebman, “Cultural techniques to manage weeds,” in Integrated weed management for sustainable agriculture, Ed: Robert Zimdahl, 2017, Burleigh Dodds Science Publishing.

SUMMARY:

The focus of this chapter is on cultural techniques that can also contribute to effective weed management strategies, including choice of crop density, crop arrangement, and crop genotype, and manipulation of initial crop size, soil fertility, and soil moisture conditions. Weed management strategies that make use of cultural factors seek to reduce weed density, resource consumption, biomass production and competition with crops. They also seek to prevent colonization of fields by weed species not previously present. Additionally, by altering the availability of light, water and nutrients in space and time, and by challenging weeds with allelochemicals, cultural tactics are intended to improve crop performance. FULL TEXT

Liebman and Gallandt, 1997

Matt Liebman and Eric Gallandt, “Many Little Hammers: Ecological Management of Crop-Weed Interactions,” In Ecology and Agriculture,” Ed: L.E. Jackson, 1997, Academic Press.

SUMMARY:

This is the first introduction of the phrase “many little hammers” to describe what is now known as integrated weed management, or IWM.  IWM relies on using a diverse assortment of weed control methods, possibly along with some herbicide use, along with changes in crop density and rotation to achieve weed control.  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.

SUMMARY:

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

Steckel, 2012

Larry Steckel, “Glyphosate-Resistant Weeds: Lessons Learned in Tennessee,” Presentation to the Iowa Soybean Association, On-Farm Network Conference, Ames, IA, February 16, 2012

SUMMARY:

Describes aggressive spread of glyphosate reisistant weeds and the importance of proactive management, including prevention and early detection and recommends herbicide protocols to control weeds. FULL TEXT

Mesnage et al., 2016

Robin Mesnage, Sarah Z. Agapito-Tenfen, Vinicius Vilperte, George Renney, Malcolm Ward, Gilles-Eric Séralini, Rubens O. Nodari & Michael N. Antoniou, “An integrated multi-omics analysis of the NK603 Roundup-tolerant GM maize reveals metabolism  disturbances caused by the transformation process,” Nature: Scientific Reports, 2016, 6:37855, DOI: 10.1038/srep37855

ABSTRACT:

Glyphosate tolerant genetically modified (GM) maize NK603 was assessed as ‘substantially equivalent’ to its isogenic counterpart by a nutrient composition analysis in order to be granted market approval. We have applied contemporary in depth molecular profiling methods of NK603 maize kernels (sprayed or unsprayed with Roundup) and the isogenic corn to reassess its substantial equivalence status. Proteome profiles of the maize kernels revealed alterations in the levels of enzymes of glycolysis and TCA cycle pathways, which were reflective of an imbalance in energy metabolism. Changes in proteins and metabolites of glutathione metabolism were indicative of increased oxidative stress. The most pronounced metabolome differences between NK603 and its isogenic counterpart consisted of an increase in polyamines including N-acetyl-cadaverine (2.9-fold), N-acetylputrescine (1.8-fold), putrescine (2.7-fold) and cadaverine (28-fold), which depending on context can be either protective or a cause of toxicity. Our molecular profiling results show that NK603 and its isogenic control are not substantially equivalent. 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.

ABSTRACT:

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.

ABSTRACT:

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

Biesecker, 2017

Michael Biesecker, “EPA, herbicide makers agree to new limits for use of dicamba,” Associated Press, October 13, 2017.

SUMMARY:

The EPA announced its deal with Monsanto, BASF and DuPont to allow dicamba use in 2018 with “tangible changes” that will be implemented in the upcoming growing season.  Dicamba will be labeled “restricted use” and applicators will be required to get additional training and certifications, and new rules will be implemented related to time of day of application and no spraying when wings are over 10 mph. The EPA worked closely with the three companies and Monsanto praised the new label restrictions, saying they are “confident the required training and record keeping can address the main causes of off-target movement.”  The EPA praises the “cooperative federalism” that brought about this agreement.  FULL TEXT

Horstmeier, 2017

Greg Horstmeier, ” Dicamba: Arkansas Plant Board Unanimously Sets Mid-April Limit,” AgFax, September 22, 2017.

SUMMARY:

The Arkansas State Plant Board reached a unanimous decision to ban dicamba use in the state from August 16 – October 31, 2018 in an attempt to mitigate damage from drift.  This would allow spring and fall burndown and pre-emergence application, but not the over the top spraying on growing crops that the new formulation and dicamba resistant seeds are engineered for.  Plus, the board passed a resolution commending the Arkansas weed scientists whose scientific integrity was questioned by Monsanto in their bid to persuade the board to reject the proposed ban.  The story includes key new information about volatility research that was presented to the board as part of the hearing process.  Herbicide industry reps continued to downplay volatility and point fingers at operator error, while independent weed scientists reported  that their findings showed that while volatility was lower immediately after spraying, volatilization continued 36 to 72 hours after application, meaning that “over time the amount of volatility between old and new formulations was not statistically different.”  The board also rejected Monsanto’s argument that drift damage appears to not have caused yield loss, and is therefore not important to address.  Board members felt this is “beyond the point when you are talking about pesticide stewardship” and bristled at Monsanto’s characterization of the proposed ban as “arbitrary and capricious.”  FULL TEXT

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