scholarly journals Seedbank and Field Emergence of Weeds in Glyphosate-Resistant Cropping Systems in the United States

Weed Science ◽  
2015 ◽  
Vol 63 (2) ◽  
pp. 425-439 ◽  
Author(s):  
Lauren M. Schwartz ◽  
David J. Gibson ◽  
Karla L. Gage ◽  
Joseph L. Matthews ◽  
David L. Jordan ◽  
...  
Keyword(s):  
United States ◽  
Species Richness ◽  
Population Density ◽  
Crop Rotation ◽  
Cropping Systems ◽  
Cropping System ◽  
The United States ◽  
Weed Population ◽  
Weed Flora ◽  
History Of

A segment of the debate surrounding the commercialization and use of glyphosate-resistant (GR) crops focuses on the theory that the implementation of these traits is an extension of the intensification of agriculture that will further erode the biodiversity of agricultural landscapes. A large field-scale study was initiated in 2006 in the United States on 156 different field sites with a minimum 3-yr history of GR-corn, -cotton or -soybean in the cropping system. The impact of cropping system, crop rotation, frequency of using the GR crop trait, and several categorical variables on seedbank weed population density and diversity was analyzed. The parameters of total weed population density of all species in the seedbank, species richness, Shannon's H′ and evenness were not affected by any management treatment. The similarity between the seedbank and aboveground weed community was more strongly related to location than management; previous year's crops and cropping systems were also important while GR trait rotation was not. The composition of the weed flora was more strongly related to location (geography) than any other parameter. The diversity of weed flora in agricultural sites with a history of GR crop production can be influenced by several factors relating to the specific method in which the GR trait is integrated (cropping system, crop rotation, GR trait rotation), the specific weed species, and the geographical location. Continuous GR crop, compared to fields with other cropping systems, only had greater species diversity (species richness) of some life forms, i.e., biennials, winter annuals, and prostrate weeds. Overall diversity was related to geography and not cropping system. These results justify further research to clarify the complexities of crops grown with herbicide-resistance traits to provide a more complete characterization of their culture and local adaptation to the weed seedbank.

Agricultural Weeds in Glyphosate-Resistant Cropping Systems in the United States

Weed Science ◽  
2013 ◽  
Vol 61 (1) ◽  
pp. 85-97 ◽  
Author(s):  
Bryan G. Young ◽  
David J. Gibson ◽  
Karla L. Gage ◽  
Joseph L. Matthews ◽  
David L. Jordan ◽  
...  
Keyword(s):  
United States ◽  
Crop Rotation ◽  
Cropping System ◽  
The United States ◽  
Agricultural Landscapes ◽  
Large Field ◽  
Categorical Variables ◽  
Weed Flora ◽  
Weed Diversity ◽  
History Of

A segment of the debate surrounding the commercialization of genetically engineered (GE) crops, such as glyphosate-resistant (GR) crops, focuses on the theory that implementation of these traits is an extension of the intensification of agriculture that will further erode the biodiversity of agricultural landscapes. A large field-scale study was conducted in 2006 in the United States on 156 different field sites with a minimum 3-yr history of GR corn, cotton, or soybean in the cropping system. The impact of cropping system, crop rotation, frequency of using the GR crop trait, and several categorical variables on emerged weed density and diversity was analyzed. Species richness, evenness, Shannon's H′, proportion of forbs, erect growth habit, and C3species diversity were all greater in agricultural sites that lacked crop rotation or were in a continuous GR crop system. Rotating between two GR crops (e.g., corn and soybean) or rotating to a non-GR crop resulted in less weed diversity than a continuous GR crop. The composition of the weed flora was more strongly related to location (geography) than any other parameter. The diversity of weed flora in agricultural sites with a history of GR crop production can be influenced by several factors relating to the specific method in which the GR trait is integrated (cropping system, crop rotation, GR trait rotation), the specific weed species, and the geographical location. The finding that fields with continuous GR crops demonstrated greater weed diversity is contrary to arguments opposing the use of GE crops. These results justify further research to clarify the complexities of crops grown with herbicide-resistance traits, or more broadly, GE crops, to provide a more complete characterization of their culture and local adaptation.

Integrating crop management and crop rotation effects into models of weed population dynamics: a review

Weed Science ◽  
1998 ◽  
Vol 46 (6) ◽  
pp. 717-728 ◽  
Author(s):  
Nathalie Colbach ◽  
Philippe Debaeke
Keyword(s):  
Population Dynamics ◽  
Life Cycle ◽  
Crop Rotation ◽  
Cultural Practices ◽  
Cropping Systems ◽  
Phenotypic Variability ◽  
Cropping System ◽  
Weed Population ◽  
Weed Population Dynamics ◽  
Weed Dynamics

Current weed demography models were reviewed to evaluate how the effects of cultural practices on weed dynamics were integrated into the models and to suggest possible ways to improve the simulation of cropping system effects. Several models were chosen to illustrate the interactions between cropping systems and weed dynamics. The first one described the structure of the weed life cycle. The second model integrated the effects of a wide set of cultural practices; the comparison of this example with other models suggested how the integration of cropping system effects could be improved. The last two models introduced the interactions of cultural practices with intraplot weed variability, either spatial variability of weed densities or genetic and phenotypic variability within weed populations. This review indicates some ways to make weed population models more comprehensive, robust, and accurate in order to improve their contribution to the evaluation and management of cropping systems.

Review of A brief history of the United States.

1919 ◽  
Vol 10 (8) ◽  
pp. 414-414
Author(s):  
No authorship indicated
Keyword(s):  
United States ◽  
The United States ◽  
History Of

An American Language

2018 ◽  
Author(s):  
Rosina Lozano
Keyword(s):  
United States ◽  
National Policy ◽  
The United States ◽  
Spanish Language ◽  
Spanish Speakers ◽  
Language Recognition ◽  
Political Language ◽  
Political Issue ◽  
History Of ◽  
The U.S

An American Language is a political history of the Spanish language in the United States. The nation has always been multilingual and the Spanish language in particular has remained as an important political issue into the present. After the U.S.-Mexican War, the Spanish language became a language of politics as Spanish speakers in the U.S. Southwest used it to build territorial and state governments. In the twentieth century, Spanish became a political language where speakers and those opposed to its use clashed over what Spanish's presence in the United States meant. This book recovers this story by using evidence that includes Spanish language newspapers, letters, state and territorial session laws, and federal archives to profile the struggle and resilience of Spanish speakers who advocated for their language rights as U.S. citizens. Comparing Spanish as a language of politics and as a political language across the Southwest and noncontiguous territories provides an opportunity to measure shifts in allegiance to the nation and exposes differing forms of nationalism. Language concessions and continued use of Spanish is a measure of power. Official language recognition by federal or state officials validates Spanish speakers' claims to US citizenship. The long history of policies relating to language in the United States provides a way to measure how U.S. visions of itself have shifted due to continuous migration from Latin America. Spanish-speaking U.S. citizens are crucial arbiters of Spanish language politics and their successes have broader implications on national policy and our understanding of Americans.

Clinical Characteristics of Patients Diagnosed with Strongyloidiasis in a United States Urban Outpatient Dermatology Department: A Case Series

2017 ◽  
Vol 1 (3) ◽  
pp. 156-160
Author(s):  
Jacqueline Watchmaker ◽  
Sean Legler ◽  
Dianne De Leon ◽  
Vanessa Pascoe ◽  
Robert Stavert
Keyword(s):  
United States ◽  
Case Series ◽  
The United States ◽  
Screening Tools ◽  
Dermatology Department ◽  
Cutaneous Manifestations ◽  
Serologic Testing ◽  
Patient Reported ◽  
History Of ◽  
Endemic Areas

Background: Although considered a tropical disease, strongyloidiasis may be encountered in non-endemic regions, primarily amongst immigrants and travelers from endemic areas.  Chronic strongyloides infection may be under-detected owing to its non-specific cutaneous presentation and the low sensitivity of commonly used screening tools. Methods: 18 consecutive patients with serologic evidence of strongyloides infestation who presented to a single urban, academic dermatology clinic between September 2013 and October 2016 were retrospectively included.  Patient age, sex, country of origin, strongyloides serology titer, absolute eosinophil count, presenting cutaneous manifestations, and patient reported subjective outcome of pruritus after treatment were obtained via chart review.  Results: Of the 18 patients, all had non-specific pruritic dermatoses, 36% had documented eosinophila and none were originally from the United States. A majority reported subjective improvement in their symptoms after treatment. Conclusion:  Strongyloides infection and serologic testing should be considered in patients living in non-endemic regions presenting with pruritic dermatoses and with a history of exposure to an endemic area.Key Points:Chronic strongyloidiasis can be encountered in non-endemic areas and clinical manifestations are variableEosinophilia was not a reliable indicator of chronic infection in this case series Dermatologists should consider serologic testing for strongyloidiasis in patients with a history of exposure and unexplained pruritus

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