Author Topic: Alternatives to the Use of Roundup Herbicide  (Read 3469 times)

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Alternatives to the Use of Roundup Herbicide
« Reply #1 on: August 31, 2011, 09:13:30 AM »
Alternatives to the Use of Roundup Herbicide

By Hector Valenzuela
Professor and Vegetable Crops Extension Specialist
Department of Plant Protection and Environmental Sciences
College of Tropical Agriculture and Human Resources
University of Hawaii at Manoa
hector@hawaii.edu

Roundup (active ingredient: Glyphosate) is among the most widely used herbicides in the world. The use of Roundup expanded over the past 15 years with the adoption of so-called Roundup-ready genetically modified (GM) crops. During the 2000s, in the U.S. the use of Roundup more than doubled, from 85-90 million pounds in 2001, to over 180 million pounds in 2007. Roundup is the most commonly used pesticide, and it is also widely used in homes, gardens, and urban settings. According to Monsanto, which produces Roundup, there are more approved uses for glyphosate (the active ingredient of Roundup), than for any other herbicide. Roundup, according to Monsanto, is used in 130 countries and on over100 different crops.
 
Herbicide tolerance represents the main trait used on genetically modified crops. In 2006, the herbicide tolerance trait represented 81% of the total acreage planted globally to genetically modified crops, representing over 200 million acres (Bonny, 2008). Today, Roundup-ready varieties represent 90% of the soybeans and 80% of the corn acreage in the U.S (Killman, 2010). Roundup Ready soybean is the most widely planted genetically modified crop, accounting for 60% of the entire global acreage planted to genetically modified crops (Bonny, 2008).
 
Recent reports have documented potential negative environmental, socioeconomic, and human health impacts from exposure to Roundup (Antoniou et al., 2011; Riley et al., 2011). Public concerns about the potential societal risks from exposure to Roundup has lead to calls for the adoption of alternative management production practices (Antoniou et al., 2011; Riley et al., 2011). Some of the proposed alternative production practices, are outlined below.
 
2.0. Development of weed resistance to Roundup herbicide
 
Conventional and GM or biotech crop farmers also need alternatives to the use of Roundup, because important weed species throughout the world are increasingly showing resistance to the use of this herbicide (Avila-Garcia and Mallory-Smith, 2011; Beckie et al., 2011; de Carvalho et al., 2011; Horstmeier, 2001; Light et al., 2011; Norsworthy et al., 2010; Owens and Powles, 2010; Rauch et al., 2010; Riar et al., 2011; Sosnoskie et al., 2011; Travlos and Chachalis, 2010). As a result of weed resistance to Roundup, farmers have to use higher rates, and conduct more frequent applications (Schutte et al., 2010). Weed resistance to Roundup may develop in as short as 3-5 years when Roundup Ready crops are grown continuously without rotations (Barbassa, 2005; Horstmeier, 2001; Van Gessel, 2001). Not only does weed resistance to Roundup reduces the efficiency of production, and increases production costs, but farmland with populations of resistant weeds may result in greater leasing or rental rates to farmers (Anon., 2004).
 



 3.0.  Alternatives to the use of Roundup are available.
 
Alternative cultural management practices are available to control weeds without the use of Roundup (Blackshaw et al., 2007). Monsanto itself recognizes that alternative management practices exist, to the use of Roundup. In the home-page of its weed management web site Monsanto acknowledges that other than Roundup, “thankfully, there are ways farmers can successfully manage tough-to-control or resistant weeds” (Monsanto, 2011). In Argentina, according to Monsanto “several agronomic practices” exist as alternatives to Roundup (Bennett, 2006).  In the U.S. according to Dale Ludwig, CEO of the Missouri Soybean Association, farmers have at their disposal "various strategies" as alternatives to the use of Roundup (Anon. 2005). Similarly, in July 2011 Weed Specialists from Iowa State University listed several alternative herbicides, and alternative management practices, that may be implemented by farmers in instances when Roundup is no longer providing effective weed control (Hartzler and Owen, 2011).
 
4.0. Alternative Herbicides to the use of Roundup
 
When weeds develop resistance to Roundup, Weed Specialists recommend alternative herbicide products to achieve effective weed control (Horstmeier, 2001; Barbassa, 2005). In fact, tank-mixes that include several herbicides, have become the norm for the past six (6) years in many crop production areas, as an alternative to the sole-reliance on Roundup (Scott, 2005; Wagoneer et al., 2011).
 
For instance, when Horseweed first showed resistance to Roundup in 2001, Specialists suggested alternatives such as crop rotations, alternative herbicides, and tillage (Horstmeier, 2001). Since then, several herbicides have been suggested as alternatives for Horseweed control (Davis et al. 2010; Kruger, 2010; Owen et al., 2011; Scott, 2005; Wagoneer et al., 2011). David Heering, the Roundup technical manager for Monsanto, also recommends the use of alternative herbicides for effective weed control (Barbassa, 2005). In comparisons of GM-cotton and non-GM/conventional systems the cost of the Roundup based herbicide program ran to about $83 per acre, while the cost for the conventional (non-Roundup) herbicide program ranged between $62 to $91 per acre (Hollis, 2009).
 
A range of alternative herbicides is available for weed control in cotton (Hollis, 2009), soybeans (Steward et al., 2010a), corn (Loux et al., 2011; Moran et al., 2011), alfalfa (Dillehay and Curran, 2010), GM beets (Wilson et al., 2011), and in roadsides (Gannon and Yelverton, 2011). Alternatives to the use of Roundup suggested by University of California Weed Specialists included soil cultivation with farm equipment, hand weeding, and the use of alternative herbicides that kill weed seeds prior to germination (Barbassa, 2005).
 
Again, Monsanto also recommends the use of alternative herbicides. For instance, Monsanto recommends the use of residual herbicides that provide “early season control.” The Monsanto weed management website explains that the use of residual herbicides  “has shown increased yields because of reduced weed pressure” (Monsanto, 2011).
 
In summary, as described above, research has shown that alternative herbicides exist to manage some of the most troublesome weeds, that have already developed resistance to Roundup (Whitaker et al., 2010).
 
5.0. Field or Cultural Management Practices as alternatives to the use of Roundup
 
Research has shown that by following an Integrated Pest or Weed Management program, ‘cultural’ practices can be adopted to effectively manage weeds on the farm (Blackshaw et al., 2007).
 
Field or cultural management practices recommended by Monsanto itself to manage weeds as alternatives to the use Roundup includes crop rotations of  “2 or more crops” and rotating to “a different crop each year” (Monsanto, 2011). Other strategies recommended by Monsanto include shifting “planting dates and fertility programs which help reduce certain difficult-to-control weeds from becoming established.” Monsanto also recommends adapting the tillage operation as well as using other herbicides with “additional modes of action which help prevent some weeds from becoming dominant in the system.”
 
The timing of weed control operations is important to minimize weed pressure late in the season. Monsanto thus recommends to “Control weeds in corn before they reach 4 inches tall and in soybeans before they reach 8 inches tall.”
 
Monsanto also highlights soil cultivation as an important alternative weed management strategy. The Monsanto website indicates that “Tillage serves as another way to control weeds and break certain weed patterns” and explains that “Tillage reduces complete reliance on herbicides. ” Furthermore, according to Monsanto “Periodic tillage can substitute for glyphosate-based burndown programs” (Monsanto, 2011).

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Below are examples of a range of alternative management practices cited in the weed science literature, to achieve effective weed control.
 
Prevention. A foremost goal of an integrated weed management program is to prevent aggressive weed species from becoming a problem in the first place. A number of strategies may be followed to prevent the introduction of weeds from outside the farm such as from machinery, farm workers, soil movement, work animals, manures and organic amendments, or the irrigation water (Christoffoleti et al., 2007). Once weeds have been introduced into the farm, preventive practices can also be taken to prevent weeds from going to seed, to reduce the population of seed-banks in the soil, and to destroy the vegetative propagules of perennial weeds (Christoffoleti et al., 2007).
 
Biofumigant cover crops for weed control, as described by Bangarwa et al. (2011b). In some instances biofumigant amendments may not be sufficient as a stand-alone strategy for weed suppression, but may be used as a component of an Integrated Weed Control program (Bangarwa et al., 2011c).
 
Biofumigant organic amendments, such as seed meal from mustard/Brassica and Sinapis cover crops, for selective weed control (Earlwine et al., 2010; Handiseni et al., 2011).
 
Biological control with arthropods and beneficial microbial organisms in crop fields, or in landscapes/turf or sods (Blossey, 2007; Boyette and Hoagland, 2010; Shabana et al., 2010; Weaver et al., 2007).
 
Cover Crops can be used as part of the rotation program to manage weed pressure, and increase cash crop competitiveness (Brainard et al., 2011; Mischler et al., 2010; Norsworthy et al., 2011; O’Reilly et al., 2011; Teasdale et al., 2007). Cover crops may help to increase the activity of weed seed predators (Ward et al., 2011). Mechanization, such as the use of roller-crimpers to terminate cover crops, and to create a thick mulch for use in no-till organic systems, facilitates the use of cover crops for weed suppression (Davis, 2010; Smith et al., 2011).
 
Cultivar or variety selection, based on growth habit, to increase competitiveness against weeds (Hutchinson et al., 2011; Spies et al., 2011; Toure et al., 2011), and for the selection of varieties that are better adapted in organic production systems (Mason et al., 2007).
 
Cultivation of fields, including precision guided mechanical cultivation systems (Fennimore et al., 2010). Cultivation plus hand-weeding in some instances may be as effective for weed suppression as the use of standard herbicide applications (Place et al., 2010).
 
Flaming with propane burners, as used in organic systems (Ulloa et al., 2010ab).
 
Increasing crop diversity, via crop rotations, or polycultures, to suppress specific weeds and increase competitiveness of the cash crop (Anderson, 2011).
 
Integrated Pest Management. The orchestrated and synergistic use of several control methods, such as those described here, rather than relying on a single component pesticide-based system (Chikowo et al., 2009; Place et al., 2010; Young et al., 2010).
 
Intercropping, polyculture, or diversified cropping systems to manage weed populations (Fernandez-Aparicio et al., 2010; Picasso et al., 2008; Saucke and Ackerman, 2006). Polycultures may include species with enhanced competitive abilities such as aromatic herbs (Dhima et al., 2010).
 
Livestock-crop systems. The adoption of integrated crop-livestock systems may help to reduce the reliance on herbicide-based systems for weed control (Tracy and Davis, 2009).
 
Living mulches, provide a protective living-barrier to suppress weed growth in high-value horticultural systems (Gibson et al., 2011).
 
Mulches, either plastic (Daugovish and Mochizuki, 2010) or biodegradable (Anzalone et al., 2010) provide a barrier to suppress weed growth.
 
Organic Weed Control strategies are increasingly being documented in the literature, as in the case of bean and sweet corn (Johnson et al., 2010).
 
Organic Amendments, may be used to manage weed populations, and to increase the competitiveness of the cash crop (Amisi and Doohan, 2010). Organic residues of allelopathic plants may also suppress weeds (Marles et al., 2010).
 
Organic herbicides such as vinegar and citric acid, used as part of an Integrated Weed Management program (Evans et al., 2011).
 
Organic mulches modify the microclimate,  provide shade, and a physical barrier to weed growth (Mischler et al., 2010; Smith et al., 2011).
 
Plant spacing and row arrangement. Increasing planting density or using narrow-rows may help to reduce weed competition (Amstrong and Sprague, 2010; Reddy and Boykin, 2010; Ryan et al., 2011; Stephenson and Brecke, 2010). The planting row-orientation may also be modified to improve weed suppression (Borger et al., 2010).
 
Polycultures. See under ‘Intercropping’.
 
Rotations. Enhancing crop diversity in the farm with rotations, is one of the most effective ways to break the life cycle of important weed species (Amuri et al., 2010; Horstmeier, 2001; Simard et al., 2011). Also see reference under ‘Increasing crop diversity.’
 
Timing of weeding operations, based on crop-growth stages, as observed with rice in Africa (Toure et al., 2011), with rice in Thailand (Sanusan et al., 2010) or with the timing of flaming treatments (Ulloa et al., 2010). Optimal weed control is obtained when weeding within the critical-weed free period that is specific for each crop species (Dillehay et al., 2011; Swanton et al., 2010).
 
Variety Selection, see under ‘Cultivar Selection.’

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6.0. References
 
Amuri, N., Kristofor R. Brye, Edward E. Gbur, Dick Oliver, and Jason Kelley. 2010. Weed Populations as Affected by Residue Management Practices in a Wheat–Soybean Double-Crop Production System. Weed Science. 58(3):234-243.
 
Anderson, R.L. 2011. Corn Tolerance to Weed Interference Varies with Preceding Crop. Weed Technology. 25(3):486-491.
 
Amisi, K.J. and Doug Doohan, 2010. Redroot Pigweed (Amaranthus retroflexus) Seedling Emergence and Growth in Soils Amended with Composted Dairy Cattle Manure and Fresh Dairy Cattle Manure under Greenhouse Conditions. Weed Technology. 24(1):71-75.
 
Anon. 2004. Survey finds increasing concern with glyphosate weed resistance. Grower Magazine. March 2004. pg. 20.
 
Anon. 2005. More Weeds Are Resistant to Monsanto's Roundup Herbicide. Chemweek’s Business Daily. October 13, 2005.
 
Antoniou, M., M.E.E. Mostafa. H.C. Vyvyan, HC. Jennings, C. Leifert Rubens, O. Nodari, C. Robinson, and J. Fagan. 2011. Roundup and birth defects: Is the public being kept in the dark?  Earth Open Source. June 2011. 52 pp.
 
Anzalone, A., A. Cirujeda, J. Aibar, G. Pardo, and C. Zaragoza. 2010. Effect of Biodegradable Mulch Materials on Weed Control in Processing Tomatoes. Weed Technology. 24(3):369-377.
 
Armstrong, J.Q., and Christy L. Sprague. 2010. Weed Management in Wide- and Narrow-Row Glyphosate-Resistant Sugarbeet. Weed Technology. 24(4):523-528.
 
Avila-Garcia, W.V. and Carol Mallory-Smith. 2011. Glyphosate-Resistant Italian Ryegrass (Lolium perenne) Populations also Exhibit Resistance to Glufosinate. Weed Science. 59(3):305-309.
 
Bangarwa, S.K., Jason K. Norsworthy, Edward E. Gbur, Jingying Zhang, and Tsehaye Habtom. 2011a. Allyl Isothiocyanate: A Methyl Bromide Replacement in Polyethylene-Mulched Bell Pepper. Weed Technology. 25(1):90-96.
 
Bangarwa, S.K., Jason K. Norsworthy, John D. Mattice, and Edward E. Gbur. 2011b. Yellow Nutsedge Interference in Polyethylene-Mulched Bell Pepper as Influenced
by Turnip Soil Amendment. Weed Technology. 25(3):466-472.
 
Bangarwa, S.K., Jason K. Norsworthy, John D. Mattice, and Edward E. Gbur. 2011. Glucosinolate and Isothiocyanate Production from Brassicaceae Cover Crops in a Plasticulture Production System. Weed Science. 59(2):247-254.
 
Barbassa, Juliana. Associated Press. 2005. Attack of the 12-foot horse weed: Herbicide-resistant strains plague California farmers. San Gabriel Valley Tribune. Aug. 10, 2005.
 
Beckie, H.J., K. Neil Harker, Linda M. Hall, Frederick A. Holm, and Robert H. Gulden. 2011. Risk Assessment of Glyphosate Resistance in Western Canada. Weed Technology. 25(1):159-164.
 
Bennett, D. 2006. Need for global stewardship: Resistant johnsongrass in Argentina. Delta Farm Press. pg. 9 ISSN: 0011-8036. September 15, 2006
 
Blackshaw, R.E, R.L. Anderson, and D. Lemerle. 2007. Cultural weed management. pp. 35-48. In: Upadhyaya, Mahesh K.; Blackshaw, Robert E (eds.) Non-Chemical Weed Management: Principles, Concepts, and Technology. CABI Publishing Wallingford, Oxon, GBR.
 
Blossey, B. 2007. Biological control of weeds using arthropods. pp. 77-92. In: Upadhyaya, Mahesh K.; Blackshaw, Robert E (eds.) Non-Chemical Weed Management: Principles, Concepts, and Technology. CABI Publishing Wallingford, Oxon, GBR.
 
Borger, C.P.D., Abul Hashem, and Shahab Pathan. 2010. Manipulating Crop Row Orientation to Suppress Weeds and Increase Crop Yield. Weed Science. 58(2):174-178.
 
Bott, S., Tsehaye Tesfamariam, Hande Candan, Ismail Cakmak, Volker Römheld and Gunter Neumann. 2008. Glyphosate-induced impairment of plant growth and micronutrient status in glyphosate-resistant soybean (Glycine max L.). Plant Soil. 312:185–194.
 
Boyette, D. and Robert E. Hoagland. 2010. Biological Control of Hemp sesbania (Sesbania exaltata) and Sicklepod (Senna obtusifolia) in Soybean with Anthracnose Pathogen Mixtures. Weed Technology. 24(4):551-556.
 
Brainard, D.C., Robin R. Bellinder, and Virender Kumar. 2011. Grass–Legume Mixtures and Soil Fertility Affect Cover Crop Performance and Weed Seed Production. Weed Technology. 25(3):473-479.
 
Chikowo, R., V. Faloya, S. Petit, and N.M. Munier-Jolain. 2009. Integrated Weed Management systems allow reduced reliance on herbicides and long-term weed control. Agriculture, Ecosystems and Environment. 132 :237–242
 
Christoffoleti, P.J., S.J.P. Carvalho, M. Nicolai, D. Doohan, and M. VanGessel. 2007. Prevention strategies in weed management. pp. 1-32. In: Upadhyaya, Mahesh K.; Blackshaw, Robert E (eds.) Non-Chemical Weed Management : Principles, Concepts, and Technology. CABI Publishing Wallingford, Oxon, GBR.
 
Daugovish, O., and Maren J. Mochizuki. 2010. Barriers Prevent Emergence of Yellow Nutsedge (Cyperus esculentus) in Annual Plasticulture Strawberry (Fragaria ananassa). Weed Technology. 24(4):478-482.
 
Davis, A.S. 2010.  Cover-Crop Roller–Crimper Contributes to Weed Management in No-Till Soybean. Weed Science. 58(3):300-309.
 
Davis, V.M., Greg R. Kruger, Bryan G. Young, and William G. Johnson. 2010. Fall and Spring Preplant Herbicide Applications Influence Spring Emergence of Glyphosate-Resistant Horseweed (Conyza canadensis). Weed Technology. 24(1):11-19.
 
de Carvalho, L.B., Hugo Cruz-Hipolito, Fidel González-Torralva, Pedro Luis da Costa Aguiar Alves, Pedro Jacob Christoffoleti, and Rafael De Prado. 2011. Detection of Sourgrass (Digitaria insularis) Biotypes Resistant to Glyphosate in Brazil. Weed Science. 59(2):171-176.
 
Dhima, K., Ioannis Vasilakoglou, Vassiliki Garane, Christos Ritzoulis, Vaia Lianopoulou, and Eleni Panou-Philotheou. 2010. Competitiveness and Essential Oil Phytotoxicity of Seven Annual Aromatic Plants. Weed Science. 58(4):457-465.
 
Dillehay, B.L. and William S. Curran. 2010. Comparison of Herbicide Programs for Weed Control in Glyphosate-Resistant Alfalfa. Weed Technology. 24:130–138
 
Dillehay, B.L., William S. Curran, and David A. Mortensen. 2011. Critical Period for Weed Control in Alfalfa. Weed Science. 59(1):68-75.
 
Earlywine, D.T., Reid J. Smeda, Travis C. Teuton, Carl E. Sams, and Xi Xiong. 2010. Evaluation of Oriental Mustard (Brassica juncea) Seed Meal for Weed Suppression
in Turf. Weed Technology. 24(4):440-445.
 
Evans, G.J., R. R. Bellinder, and R. R. Hahn. 2011. Integration of Vinegar for In-Row Weed Control in Transplanted Bell Pepper and Broccoli. Weed Technology. 25(3):459-465.
 
Fennimore, S.A., Laura Tourte, John S. Rachuy, Richard F. Smith, and Christina George. 2010. Evaluation and Economics of a Machine-Vision Guided Cultivation Program in Broccoli and Lettuce. Weed Technology. 24(1):33-38.
 
Fernández-Aparicio, M., A.A. Emeran , and D. Rubiales. 2010. Inter-cropping with berseem clover (Trifolium alexandrinum) reduces infection by Orobanche crenata in legumes. Crop Protection. 29:867-871.
 
Gannon, T.W. and Fred H. Yelverton. 2011. Application Placement Equipment for Bahiagrass (Paspalum notatum) Suppression along Roadsides. Weed Technology. 25(1):77-83.
 
Gibson, K.D., John McMillan, Stephen G. Hallett, Thomas Jordan, and Stephen C. Weller. 2011. Effect of a Living Mulch on Weed Seed Banks in Tomato. Weed Technology. 25(2):245-251.
 
Handiseni, M., Jack Brown, Robert Zemetra, and Mark Mazzola. 2011.  Herbicidal Activity of Brassicaceae Seed Meal on Wild Oat (Avena fatua), Italian Ryegrass (Lolium multiflorum), Redroot Pigweed (Amaranthus retroflexus), and Prickly Lettuce (Lactuca serriola). Weed Technology. 25(1):127-134.
 
Hartzler, R. and Micheal Owen. 2011. Managing Glyphosate Failures. Iowa State Univ. Coop. Extension Service. Accessed August 28, 2011 from: http://www.extension.iastate.edu/CropNews/2011/0715hartzler.htm
 
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Horstmeier, G.D. 2001. Roundup Resistance. Glyphosate-resistant marestail found in Delaware. Farm Journal. April 2001.
 
Hutchinson, P.J.S., Brent R. Beutler, and JaNan Farr. 2011. Hairy Nightshade (Solanum sarrachoides) Competition with Two Potato Varieties. Weed Science. 59(1):37-42.
 
Johal, G.S. and D.M. Huber. 2009. Glyphosate effects on diseases of plants. Europ. J. Agronomy 31:144–152
 
Johnson, H.J., Jed B. Colquhoun, Alvin J. Bussan, and Richard A. Rittmeyer. 2010. Feasibility of Organic Weed Management in Sweet Corn and Snap Bean for Processing. Weed Technology. 24(4):544-550.
 
Kilman, S. 2010. Superweeds Hit Farm Belt, Triggering New Arms Race. Wall Street Journal. (Eastern edition). New York, N.Y.: Jun 4, 2010. pg. A.1
 
Kruger, G.R., Vince M. Davis, Stephen C. Weller, and William G. Johnson. 2010. Control of Horseweed (Conyza canadensis) with Growth Regulator Herbicides. Weed Technology. 24(4):425-429.


Pasture/Range Management

 
Light, G.G., M. Y. Mohammed, P. A. Dotray, J. M. Chandler, and R. J. Wright. 2011. Glyphosate-Resistant Common Waterhemp (Amaranthus rudis) Confirmed in
Texas. Weed Technology. 25(3):480-485.
 
Loux, M.M., Anthony F. Dobbels, William G. Johnson, and Bryan G. Young. 2011. Effect of Residual Herbicide and Postemergence Application Timing on Weed Control and Yield in Glyphosate-Resistant Corn. Weed Technology. 25(1):19-24.
 
Marles, S.M., Thomas D. Warkentin, and Frederick A. Holm. 2010. Field Pea Seed Residue: a Potential Alternative Weed Control Agent. Weed Science 58(4):433-441.
 
Mason, H.E., Alireza Navabi, Brenda L. Frick, John T. O’Donovan, and Dean M. Spaner. 2007. The Weed-Competitive Ability of Canada Western Red Spring Wheat Cultivars Grown under Organic Management. Crop Sci. 47:1167–1176
 
Melcer, Rachel. 2005. Misuse of gene-altered crops can cause problem. St. Louis Post-Dispatch. Oct. 9, 2005.
 
Mischler, R.A., William S. Curran, Sjoerd W. Duiker, and Jeffrey A. Hyde. 2010. Use of a Rolled-rye Cover Crop for Weed Suppression in No-Till Soybeans. Weed Technology. 24(3):253-261.
 
Monsanto. 2011. Weed management. Accessed August 27, 2011. http://www.monsanto.com/weedmanagement/Pages/default.aspx
 
Moran, M., Peter H. Sikkema, and Clarence J. Swanton. 2011. Efficacy of Saflufenacil plus Dimethenamid-P for Weed Control in Corn. Weed Technology. 25(3):330-334.
 
Norsworthy, J.K. Prashant Jha, Lawrence E. Steckel, and Robert C. Scott. 2010. Confirmation and Control of Glyphosate-Resistant Giant Ragweed (Ambrosia
trifida) in Tennessee. Weed Technology. 24(1):64-70.
 
Norsworthy, J.K., Marilyn McClelland, Griff Griffith, Sanjeev K. Bangarwa, and Joshua Still. 2011. Evaluation of Cereal and Brassicaceae Cover Crops in Conservation-Tillage, Enhanced, Glyphosate-Resistant Cotton. Weed Technology. 25(1):6-13.
 
O'Reilly, K.A., Darren E. Robinson, Richard J. Vyn, and Laura L. Van Eerd. 2011.  Weed Populations, Sweet Corn Yield, and Economics Following Fall Cover Crops. Weed Technology. 25(3):374-384.
 
Owen, M.J. and Stephen B. Powles. 2010. Glyphosate-Resistant Rigid Ryegrass (Lolium rigidum) Populations in the Western Australian Grain Belt. Weed Technology. 24(1):44-49.
 
Owen, L.N., Thomas C. Mueller, Christopher L. Main, Jason Bond, and Lawrence E. Steckel . 2011. Evaluating Rates and Application Timings of Saflufenacil for Control of Glyphosate-Resistant Horseweed (Conyza canadenis) Prior to Planting No-Till Cotton. Weed Technology. 25(1):1-5.
 
Picasso, V.D., E. Charles Brummer, Matt Liebman, Philip M. Dixon, and Brian J. Wilsey. 2008. Crop Species Diversity Affects Productivity and Weed Suppression in Perennial Polycultures under Two Management Strategies. Crop Sci. 48:331–342
 
Place, G.T., S. C. Reberg-Horton, and D. L. Jordan. 2010. Interaction of Cultivar, Planting Pattern, and Weed Management Tactics in Peanut. Weed Science. 58(4):442-448.
 
Rauch, T.A., Donald C. Thill, Seth A. Gersdorf, and William J. Price. 2010. Widespread Occurrence of Herbicide-Resistant Italian Ryegrass (Lolium multiflorum) in Northern Idaho and Eastern Washington. Weed Technology. 24(3):281-288.
 
Riar, D.S., Jason K. Norsworthy, Dennis B. Johnson, Robert C. Scott, and Muthukumar Bagavathiannan. 2011. Glyphosate Resistance in a Johnsongrass (Sorghum halepense) Biotype from Arkansas. Weed Science. 59(3):299-304.
 
Riley, P., Dr. Janet Cotter, Marco Contiero, Dr Meriel Watts. 2011. Herbicide tolerance and GM crops: Why the world should be Ready to Round Up glyphosate. Greenpeace and Gmfreeze. Technical Note 03/2011GRL-TN 03/2011, Amsterdam. 44 pp.
 
Ryan, M.R., Steven B. Mirsky, David A. Mortensen, John R. Teasdale, and William S. Curran. 2011. Potential Synergistic Effects of Cereal Rye Biomass and Soybean Planting Density on Weed Suppression. Weed Science. 59(2):238-246.
 
Sanusan, S., Anan Polthanee, Alain Audebert, Surasak Seripong, and Jean-Claude Mouret. 2010. Suppressing weeds in direct-seeded lowland rainfed rice: Effect of cutting dates and timing of fertilizer application Crop Protection 29:927-935
 
Saucke, H & K. Ackermann. 2006. Weed suppression in mixed cropped grain peas and false flax (Camelina sativa). Weed Research. 46, 453–461.
 
Schutte, B.J., Aaron G. Hager, and Adam S. Davis. 2010. Respray Requests on Custom-Applied, Glyphosate-Resistant Soybeans in Illinois: How Many and Why Weed Technology. 24(4):590-598.
 
Shabana, Y.M., Carol M. Stiles, R. Charudattan, and Ayman H. Abou Tabl. 2010. Evaluation of Bioherbicidal Control of Tropical Signalgrass, Crabgrass, Smutgrass, and Torpedograss. Weed Technology. 24(2):165-172.
 
Simard, M.J., Sébastien Rouane, and Gilles D. Leroux. 2011. Herbicide Rate, Glyphosate/Glufosinate Sequence and Corn/Soybean Rotation Effects on Weed Seed Banks. Weed Science. 59(3):398-403.
 
Smith, A.N., S. Chris Reberg-Horton, George T. Place, Alan D. Meijer, Consuelo Arellano, and J. Paul Mueller. 2011. Rolled Rye Mulch for Weed Suppression in Organic No-Tillage Soybeans. Weed Science. 59(2):224-231.
 
Sosnoskie, L.M., Jeremy M. Kichler, Rebekah D. Wallace, and A. Stanley Culpepper. 2011. Multiple Resistance in Palmer Amaranth to Glyphosate and Pyrithiobac Confirmed in Georgia. Weed Science. 59(3):321-325.
 
Spies, J.M., T. D. Warkentin, and S. J. Shirtliffe. 2011. Variation in Field Pea (Pisum sativum) Cultivars for Basal Branching and Weed Competition. Weed Science. 59(2):218-223.
 
Stephenson IV, D.O. and Barry J. Brecke. 2010. Weed Management in Single- vs. Twin-Row Cotton (Gossypium hirsutum). Weed Technology. 24(3):275-280.
 
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