Weed resistance escalating in Iowa and Argentina
2.Weed Resistance To Herbicide Increasing in Iowa
NOTE: GM herbicide resistant crops were pushed to farmers as the simple and convenient way to achieve effective weed management, but now...
EXTRACTS: "Anything that is suggested to be simple and convenient (herbicide, crop trait, whatever) will inevitably fail and cost you yield potential." - item 2
...no preventive strategies are deployed against the invasion of [glyphosate resistant] johnsongrass. Instead, the reactive measures are based on "gene-stacking" that allows the use of still more glyphosate or new combinations of herbicides, thus combining the pesticide treadmill with a novel "transgenic treadmill". - item 1
1.Weed resistance to glyphosate in genetically modified (GM) soybean cultivation in Argentina
Universitat Autonoma de Barcelona, 27 May 2009
The rapid expansion of industrial agriculture and the globalization of the food system have favoured the decline and deterioration of agro-ecosystems thus increasing biodiversity loss. An article recently published in GEOFORUM analyzes the consequences of the emergence of glyphosate resistance in johnsongrass, a weed that is affecting GM soybeans fields in northern Argentina.
The article written by Rosa Binimelis, Walter Pengue and Iliana Monterroso, is the product of collaborative work among the Autonomous University of Barcelona, University of Buenos Aires and the Latin American Faculty of Social Sciences in Guatemala. The article describes the geographical advance of the invasion beyond the Pampas, it reviews the environmental history of the invasion process to discuss the major drivers and pressures in the context of the changes of the agriculture of Argentina in the last twenty years. It discusses how the process of agricultural modernization in Argentina has resulted in the intensification of crops via sophisticated technological packages including an increase use of inputs and the adoption of GMOs.
In 2007, the historical records for soybean yield and price in Argentina were reached, to some extent due to the sharply escalating biofuels demand. Nevertheless, if more genetic-resistant weeds appear, the benefits derived from the model could be lost. Results highlight the socio-economic impacts and responses associated with invasive species affecting agro-biodiversity. They indicate that no preventive strategies are deployed against the invasion of johnsongrass. Instead, the reactive measures are based on "gene-stacking" that allows the use of still more glyphosate or new combinations of herbicides, thus combining the pesticide treadmill with a novel "transgenic treadmill".
The article also evidences the need to further analyze how policies in other regions affect the management of a biodiversity issue, for instance the EU Directive 2003/30/EC (8 May 2003) on the promotion of the use of biofuels for transport. Therefore, this study has policy relevance also for the European Union. The EU is a large importer of soybeans from Argentina. European awareness of the local impacts of imported soybeans (as feedstuffs and/or agro-fuels) should not focus only on deforestation. It should take the findings of this study into account.
This article was written as part of the research conducted at ICTA-UAB and FLACSO-Guatemala for the European project ALARM (2004-2009), on risks to biodiversity.
* Full bibliographic informationArticle published in GEOFORUM, available on line since April 28, 2009; http://dx.doi.org/10.1016/j.geoforum.2009.03.009
2.Weed Resistance To Herbicide Increasing
Wallaces Farmer, 12 April 2011
Despite the almost universal adoption of genetically engineered crops, specifically those resistant to glyphosate herbicide, weed problems in Iowa continue to be important and actually, they are getting worse.
That's the observation and latest thinking of Iowa State University Extension weed scientist Mike Owen. He made those comments at the end of the day, as he summed up presentations that were made by weed researchers from the University of Illinois and Iowa State University at a March 31, 2011 conference on weed resistance held at Davenport, Iowa.
Researchers from herbicide companies and seed companies also voiced their opinions and gave their recommendations, regarding the causes of and possible solutions to this increasing problem.
Weeds are continuing to evolve and develop resistance
He says resistant populations of weeds are continuing to evolve and develop resistance to more herbicides. Weed resistance to glyphosate is a growing problem. And other herbicides are being added to the resistance list. For example, resistance to HPPD inhibitor herbicides was documented in seed corn fields. "I suspect resistance to this herbicide group is more widely distributed than most farmers realize," says Owen.
He says it's crucial for farmers, chemical dealers, crop consultants and everyone involved in weed mangement to take steps to help prevent further spread or development of herbicide resistant weeds. "In Iowa we now have resistance in waterhemp to triazine herbicides, ALS inhibitors, PPO inhibitors, glyphosate and HPPD inhibitor herbicides," he adds.
Weeds are most important pest Iowa farmers face each year
Proper weed management will make farmers more money every year than managing any other pest. Diversity of tactics is the key. "Weeds represent the most important and economically damaging pest that Iowa soybean and corn farmers face every year," Owen says.
Evolved resistance to herbicides continues to escalate in Iowa. Glyphosate-resistant populations of waterhemp are widespread and increasing. Similarly, glyphosate-resistance in giant ragweed and marestail are becoming increasingly important. Last year, resistance to HPPD inhibitor herbicides (products such as Laudis, Callisto and Impact) was documented in seed corn production fields.
"I suspect that resistance to this herbicide group is more widely distributed than most growers realize. Thus in Iowa, we have resistance in waterhemp to the triazine herbicides (atrazine), ALS inhibitors (Pursuit), PPO inhibitors (Phoenix), glyphosate and now the HPPD inhibitor herbicides," he notes.
If you aren't getting control of waterhemp, presume it's resistant
Furthermore, many populations of waterhemp have multiple herbicide resistances, he adds. As the number of herbicides to which waterhemp is resistant increases, the difficulty in managing this important weed decreases. "If you are not sure if waterhemp in your fields is herbicide resistant, you are better erring on the side of being conservative," says Owen. "You should presume resistance exists and manage accordingly."
Several representatives from herbicide companies and seed companies also gave presentations and shared their thoughts at the Davenport meeting. Owen offered the following observations and recommendations to farmers and those who advise farmers regarding weed management practices and products.
Steps to help control spread of herbicide resistance in weeds
* DO NOT use only one management tactic or herbicide to control weeds.
* DO use tank-mixes of herbicides with different mechanisms of action (MOAs) that will control the weeds of concern. Tank mixes are better than rotation of MOAs. Refer to the herbicide group number (voluntarily included on many herbicide labels) to determine if the herbicides have different MOAs.
* DO scout early in the spring and continue to scout throughout the season. While you may not think weeds exist in the untilled fields, look closer because they are there and they will cost you money if you do not manage them prior to or IMMEDIATELY after planting.
* DO use a soil-applied residual herbicide on all acres regardless of crop or trait. Whether your plan to till the fields or not, it would be worthwhile to include a residual herbicide that controls the weeds that will germinate first, are most populous, and are of greatest concern.
* DO know what herbicides you are planning to use, what they control (and do not control), what replant restrictions exist and if there is significant potential for crop injury.
Correct management of weeds will make you more money every year
"Correct management of weeds will make you more money every year than managing any other pest complex," Owen emphasizes. "Weeds are universal and exist in economic populations on most, if not all fields in Iowa. Herbicide-resistant weed populations are increasing at an increasing rate in Iowa; these weed shifts are the result of the management decisions you make.
"Anything that is suggested to be simple and convenient (herbicide, crop trait, whatever) will inevitably fail and cost you yield potential," he adds. "No single tactic will protect the potential crop yield nor deter the evolution of herbicide-resistant weed populations. Be proactive and manage herbicide resistance before it becomes a major problem. Diversity of tactics is the key to consistent weed management and high crop yields."