Dear Friends and colleagues,
RE: As Weed Resistance Grows, GM Herbicide-Tolerant Crops Fast Becoming Useless
Weeds in GM cotton fields in the US have developed resistance to the herbicide glyphosate to such an extent that this could threaten the sustainable use of glyphosate-resistant crop technology, according to a new study published in the Proceedings of the National Academy of Sciences journal. (Items 1 and 2)
This highlights the growing number of cases of GM crops developing resistance to the popular chemical used by numerous GM farmers around the world, most of whom grow Monsanto’s GM crops which are developed to resist the company’s Roundup herbicide.
In its new report (Item 3), GM Freeze said overuse of Monsanto’s best selling product on monocultures employing zero tillage has created the conditions for weeds to evolve resistance very rapidly. It cited three examples of Roundup resistant weeds, namely Johnsongrass in Argentina, Horseweed and Palmer amaranth in the USA, which have infest thousands of acres where GM soya is grown. Weeds have also developed multiple resistance to two or more different types of weed killers, thus farmers are fast running out of herbicides to kill them.
The race to develop more chemical-based herbicides needs to end and a non-chemical method of weed control is the only solution to long-term, sustainable farming, according to the report.
With best wishes,
Third World Network
131 Jalan Macalister,
10400 Penang ,
Website: www.biosafety-info.net and www.twnside.org.sg
GM cotton crops in US useless
By Will Ockenden
ABC, 12 January 2010
Genetically modified cotton crops in the United States are becoming
useless, as weeds evolve a resistance to the herbicide glyphosate.
In the southern cotton crops, mutant weeds are becoming so bad mechanical harvesters are being damaged, and weed control must be done by hand.
A scientific study has found that the herbicide resistant weed population could threaten GM crop technology.
The study was published in the Proceedings of the National Academy of Sciences journal.
In this report: Dr Todd Gains, study’s lead author, University of Western Australia
Gene amplification confers glyphosate resistance in Amaranthus palmeri Proc. Natl. Acad. Sci. USA 2010 107:955-956
1. Todd A. Gaines(a), (1)
2. Wenli Zhang(b),
3. Dafu Wang(c),
4. Bekir Bukun(a),
5. Stephen T. Chisholm(a),
6. Dale L. Shaner(d),
7. Scott J. Nissen(a),
8. William L. Patzoldt(e),
9. Patrick J. Tranel(e),
10. A. Stanley Culpepper(f),
11. Timothy L. Grey(f),
12. Theodore M. Webster(g),
13. William K. Vencill(h),
14. R. Douglas Sammons(c),
15. Jiming Jiang(b),
16. Christopher Preston(i),
17. Jan E. Leach(a) and
18. Philip Westra(a),
1. (a) Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins , CO 80523 2. (b) Department of Horticulture, University of Wisconsin , Madison , WI
3. (c) Monsanto Company, St. Louis , MO 63167
4. (d) Water Management Research Unit, US Department of Agriculture Agricultural Research Service (USDA-ARS), Fort Collins, CO 80526 5. (e)Department of Crop Sciences, University of Illinois , Urbana , IL
6. (f) Crop and Soil Science Department, University of Georgia , Tifton , GA 31794 7. (g) Crop Protection and Management Research Unit, USDA-ARS, Tifton , GA
8. (h) Crop and Soil Science Department, University of Georgia , Athens , GA 30602 9. (i) School of Agriculture , Food and Wine, University of Adelaide , Glen Osmond, SA 5064, Australia
(1) Present address: Western Australian Herbicide Resistance Initiative, School of Plant Biology , University of Western Australia , Crawley , WA 6009, Australia .
1. Edited by Charles J. Arntzen, Arizona State University , Tempe , AZ , and approved October 29, 2009 (received for review June 16, 2009 )
The herbicide glyphosate became widely used in the United States and other
parts of the world after the commercialization of glyphosate-resistant crops. These crops have constitutive overexpression of a glyphosate-insensitive form of the herbicide target site gene, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Increased use of glyphosate over multiple years imposes selective genetic pressure on weed populations. We investigated recently discovered glyphosate-resistant Amaranthus palmeri populations from Georgia , in comparison with normally sensitive populations. EPSPS enzyme activity from resistant and susceptible plants was equally inhibited by glyphosate, which led us to use quantitative PCR to measure relative copy numbers of the EPSPS gene. Genomes of resistant plants contained from 5-fold to more than 160-fold more copies of the EPSPS gene than did genomes of susceptible plants. Quantitative RT- PCR on cDNA revealed that EPSPS expression was positively correlated with genomic EPSPS relative copy number. Immunoblot analyses showed that increased EPSPS protein level also correlated with EPSPS genomic copy number. EPSPS gene amplification was heritable, correlated with resistance in pseudo-F2 populations, and is proposed to be the molecular basis of glyphosate resistance. FISH revealed that EPSPS genes were present on every chromosome and, therefore, gene amplification was likely not caused by unequal chromosome crossing over. This occurrence of gene amplification as an herbicide resistance mechanism in a naturally occurring weed population is particularly significant because it could threaten the sustainable use of glyphosate-resistant crop technology.
* (2) To whom correspondence should be addressed at: Department of
Bioagricultural Sciences and Pest Management, 1177 Campus Delivery,
Colorado State University, Fort Collins, CO 80523. E-mail:
* Author contributions: T.A.G., S.T.C., S.J.N., J.J., C.P., J.E.L., and P.W.
designed research; T.A.G., W.Z., D.W., and B.B. performed research; D.L.S., W.L.P., P.J.T., A.S.C., T.L.G., T.M.W., W.K.V., and R.D.S. contributed new reagents/analytic tools; T.A.G. analyzed data; and T.A.G. wrote the paper.
* The authors declare no conflict of interest. This article is a PNAS Direct Submission.
* This article contains supporting information online at www.pnas.org/cgi/content/full/0910081107/DCSupplemental
GM Herbicide Tolerant Crops Escalate the Herbicide Arms Race
GM Freeze, Immediate release: 19 January 2010
Farmers urged to take lead on herbicide resistant weeds and adopt non-chemical approach
A new report  on the spread of herbicide resistant weeds in the world calls upon farmers to take the lead in dealing with the problem if scientists and governments fail to do so. Without such action GM herbicide tolerant crops will cause an explosion of herbicide resistant weeds.
Promises from agri-biotech companies that GM herbicide tolerant crops would make weed control in crops such as soya, maize and cotton easier and cheaper now look hollow. This year the GM industry will again try to use the ISAAA report to paper over the cracks and paint GM as a success in world agriculture. This research shows exactly how much more costly HT crops are becoming over time as serious problems spread.
GM Freeze has reviewed the latest evidence on weeds resistant to one or more weed killers in the report published today. The rapid increase in weed resistance, and the key role played by GM herbicide tolerant (GMHT) crops that encourage farmers to depend on one herbicide (Monsanto’s Roundup), are highlighted. Overuse of Monsanto’s best selling product on monocultures employing zero tillage has created the conditions for weeds to evolve resistance very rapidly.
Three examples of Roundup resistant weeds highlighted in the report (Johnsongrass in Argentina , Horseweed and Palmer amaranth in the USA ) are now all resistant to Roundup and infest thousands of acres where GMHT soya is grown. Farmers are attempting to control them using cocktails of weed killers, which in Argentina includes spraying them from the air. This has serious implications for the local people and environment because spray drifts off target into villages and other crops.
The report also highlights the problem of weeds with multiple resistance to two or more different types of weed killers, including Roundup, in the US soya and maize belt. The options to rotate the use of different weed killers, to spray mixtures of weed killers or to use soil acting weed killers to kill off problem weeds as they germinate are limited by weeds that have already evolved resistance during decades of chemical weed control.
The complexity of planning weed control on all crops will increase as resistance grows. Weed control costs are rising steeply. There is no prospect for development in the next 5-10 years of an effective, new, safe chemical weed killer to substitute for Roundup or other products with resistance problems.
The report calls for greater use of agroecological methods of weed control, including cover crop planting (such clover), crop rotation, crop breaks, mulching with cover crops and other organic materials and mechanical methods. It concludes:
The weed control and monoculture systems adopted for GMHT crops ignore these good agricultural principles and practices despite the fact that “farmers who practice continuous cropping, or intensive cropping, run a much greater risk of developing resistance”.[2 ]
Pete Riley of GM Freeze said:
“We are fast running out of chemicals that kill weeds thanks to overuse and poor farming practices. GM herbicide tolerant crops are accelerating the problem, and before too long chemical weed control options could be very limited in some areas. It only requires one weed to develop Roundup resistance for chemical use to escalate. People in Argentina are already facing frequent bouts of aerial spraying with mixtures of weed killers. This is not good for people, the environment or farming.
“Farmers need to make certain that non-chemical weed control methods are being developed in research institutions. They cannot rely on agro-chemical companies and governments to solve a problem they helped create, as all they have to offer is yet more chemicals. We need a revolution in agricultural research and arable farming to make sure we put an end to the pesticides arms race and adopt sustainable approaches to weed control based on agroecology.”
Calls to Pete Riley 07903 341065 or 0845 217 8992
 To view the full report see
 Chaudhry O, 2008. Herbicide Resistance and Weed-Resistance Management.