U.S. Grower Views on Problematic Weeds and Changes in Weed Pressure in Glyphosate-Resistant Corn, Cotton, and Soybean Cropping Systems

Kruger, Greg R.; Johnson, William G.; Weller, Stephen C.; Owen, Micheal D. K.; Shaw, David R.; Wilcut, John W.; Jordan, David L.; Wilson, R. G.; Bernards, Mark L.; Young, Bryan G.

doi:10.1614/wt-08-040.1

Cited by 76 publications

(82 citation statements)

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“…Weed shifts toward glyphosate-resistant and glyphosatetolerant weed species in a glyphosate-based management system has been widely documented (Kruger et al 2009;Norsworthy 2008;Norsworthy et al 2012). Evolution and spread of glyphosate-resistant Palmer amaranth (Norsworthy (Koger et al 2004), and Italian ryegrass (Nandula et al 2012) biotypes and inherent tolerance of morninglory, hemp sesbania, and prickly sida (Jordan et al 1997;Riar et al 2011a) to glyphosate is most likely the reason for the dominance of these weed species in glyphosate-based soybean systems in the midsouth.…”

Section: Resultsmentioning

confidence: 99%

Assessment of Weed Management Practices and Problem Weeds in the Midsouth United States—Soybean: A Consultant's Perspective

et al. 2013

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Th is report explores the impact of the adoption of genetically engineered (GE) corn, soybean, and cotton on pesticide use in the United States, drawing principally on data from the United States Department of Agriculture. Th e most striking fi nding is that GE crops have been responsible for an increase of 383 million pounds of herbicide use in the U.S. over the fi rst 13 years of commercial use of GE crops (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008).Th is dramatic increase in the volume of herbicides applied swamps the decrease in insecticide use attributable to GE corn and cotton, making the overall chemical footprint of today' s GE crops decidedly negative. Th e report identifi es, and discusses in detail, the primary cause of the increase --the emergence of herbicide-resistant weeds.Th e steep rise in the pounds of herbicides applied with respect to most GE crop acres is not news to farmers. Weed control is now widely acknowledged as a serious management problem within GE cropping systems. Farmers and weed scientists across the heartland and cotton belt are now struggling to devise aff ordable and eff ective strategies to deal with the resistant weeds emerging in the wake of herbicide-tolerant crops.But skyrocketing herbicide use is news to the public at large, which still harbors the illusion, fed by misleading industry claims and advertising, that biotechnology crops are reducing pesticide use. Such a claim was valid for the fi rst few years of commercial use of GE corn, soybeans, and cotton. But, as this report shows, it is no longer.An accurate assessment of the performance of GE crops on pesticide use is important for reasons other than correcting the excesses of industry advertising. It is also about the future direction of agriculture, research, and regulatory policy.Herbicides and insecticides are potent environmental toxins. Where GE crops cannot deliver meaningful reductions in reliance on pesticides, policy makers need to look elsewhere. In addition to toxic pollution, agriculture faces the twin challenges of climate change and burgeoning world populations. Th e biotechnology industry' s current advertising campaigns promise to solve those problems, just as the industry once promised to reduce the chemical footprint of agriculture. Before we embrace GE crops as solution to these new challenges, we need a sober, data-driven appraisal of its track record on earlier pledges.Th e government has the capability, and we would argue a responsibility, to conduct periodic surveys of suffi cient depth to track and accurately quantify the impacts of GE crops on major performance parameters, including pesticide use. While the USDA continued to collect farm-level data on pesticide applications during most of the 13 years covered in this report, the Department has been essentially silent on the impacts of GE crops on pesticide use for almost a decade. Th is is why the groups listed in the Acknowledgements commissioned this study by Dr. Benbrook, the third he has done on this t...

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Section: Resultsmentioning

confidence: 99%

Assessment of Weed Management Practices and Problem Weeds in the Midsouth United States—Soybean: A Consultant's Perspective

et al. 2013

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“…Weed community factors hypothesized to correlate with respray requests included the presence of weed species previously noted as problematic in direct-mail surveys and one-on-one interviews (Gibson et al 2005Kruger et al 2009), comparatively high weed densities across the entire field, an abundance of weeds visible from roadsides, patches characterized by high weed densities, and evidence of custom application failure. Once weed community factors associated with glyphosate respray requests were identified, a metaanalysis employing published studies on soybean yield reduction in response to increasing weed density was utilized to project impacts of respray-request-driving weed communities in both respray-requested and nonrequested fields.…”

mentioning

confidence: 99%

Respray Requests on Custom-Applied, Glyphosate-Resistant Soybeans in Illinois: How Many and Why

2010

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If an herbicide application fails to control a targeted weed community sufficiently, farmers may try to eliminate surviving weeds with a follow-up application (hereafter “respray”). Despite the implications of resprays on the spread of herbicide-resistant weeds, respray frequencies and causal factors are poorly understood. A two-part survey of glyphosate-resistant soybean fields and custom application services was conducted in Illinois during 2005 and 2006 to determine the relative frequency of respray requests for postemergence glyphosate, and to identify weed community factors associated with glyphosate respray requests. A meta-analysis was then utilized to project the impacts of weed community factors driving respray requests on crop yield. Glyphosate resprays were requested for 14% of surveyed fields in both 2005 (n= 43) and 2006 (n= 90). In 2005, respray requests were highly associated with both population densities of weed communities visible from roadsides and incidences of skips (i.e., rectangular areas of escaped weeds indicating custom application failure). A skip increased the odds of respray request by more than ninefold, and population densities of weed communities visible from roadsides were, on average, 2.5 times greater in respray-requested fields compared with nonrequested fields. In 2006, respray requests were associated with population densities of weed communities identified by walking through fields. Contrary to 2005, requests in 2006 were concentrated in those fields with low weed population densities. Prior to resprays, weed communities capable of causing substantial soybean yield loss were present in both respray-requested and nonrequested fields in 2005 but in only nonrequested fields in 2006. Although this investigation indicated that custom applicators can take actions to reduce respray requests (i.e., avoiding skips), farmers and custom applicators should be prepared to implement additional weed control after postemergence glyphosate applications because damaging weed communities may remain.

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“…The historic lack of integrated weed management (IWM) by growers has sped the frequency of the problems ). Importantly, the likelihood of growers adopting cultural and mechanical strategies is low (Green and Owen 2010;Kruger et al 2009). Furthermore, given the cross and multiple resistances that have evolved in important weeds, the numbers of herbicides that will provide effective control are limited.…”

Section: Implications Of Glyphosate Resistant Weedsmentioning

confidence: 99%

Weed resistance development and management in herbicide-tolerant crops: experiences from the USA

Owen

2011

J. Verbr. Lebensm.

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The evolution of weeds in USA agroecosystems predates herbicide tolerant (HT) crops by several decades. However, given the unprecedented adoption of genetically engineered (GE) HT crops, particularly in maize, cotton and soybean and the concomitant use of glyphosate, the evolution of glyphosate-resistant (GR) biotypes of agronomic important weeds now represents a significant threat to the sustainability of the GE HT trait and the herbicide. Notably, GR biotypes of horseweed (Conyza canadensis), common waterhemp (Amaranthus tuberculatus), Palmer pigweed (Amaranthus palmeri), giant ragweed (Ambrosia trifida) and johnsongrass (Sorghum halepense) have increased dramatically in frequency in conjunction with the adoption of crop production systems based on GE HT crops. Furthermore, other shifts in weed communities have been observed. It must be emphasized that the GE HT crops did not directly cause these weed shifts. The industry was responsible initially for these changes in weed communities given their initial positions that the glyphosate-resistant weed problems were unlikely to evolve and the recommendations to use glyphosate exclusively for weed management. However, decisions by growers to use glyphosate must be factored in as imparting selection pressure on the weed communities resulting in weed management problems, particularly when university recommendations strongly suggested not to use glyphosate in this manner. The key is now to provide growers with sufficient information to convince them to adopt integrated weed management programs and utilize best management practices. Given the presumed and real benefits of convenience and simplicity of the GE HT crop production systems; this will be a difficult task.

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U.S. Grower Views on Problematic Weeds and Changes in Weed Pressure in Glyphosate-Resistant Corn, Cotton, and Soybean Cropping Systems

Cited by 76 publications

References 20 publications

Assessment of Weed Management Practices and Problem Weeds in the Midsouth United States—Soybean: A Consultant's Perspective

Assessment of Weed Management Practices and Problem Weeds in the Midsouth United States—Soybean: A Consultant's Perspective

Respray Requests on Custom-Applied, Glyphosate-Resistant Soybeans in Illinois: How Many and Why

Weed resistance development and management in herbicide-tolerant crops: experiences from the USA

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