Canada Confirms Firsf Cases Of Roundup Resistant Weed

From a press release

WINNIPEG, MANITOBA - University of Guelph weed scientists have completed evaluations of a giant ragweed (Ambrosia trifida) population in Ontario and can now confirm the first case of a glyphosate-resistant weed in Canada.

"We have been able to demonstrate that plants from this population of giant ragweed meet all five requirements necessary to confirm resistance, including surviving increased rates of glyphosate and the ability to pass resistance along to the next generation," said Dr. François Tardif of the department of plant agriculture at the University of Guelph.

The population in question underwent both greenhouse and field testing by university researchers, working in conjunction with Monsanto Canada, in order to confirm resistance. While over 30 other species of weeds in Canada have developed resistance to herbicides, this is the first confirmation of a glyphosate-resistant weed in Canada. In other countries around the world, 17 weed species – including giant ragweed – have been confirmed as resistant to glyphosate. Ten of those species are in the United States. All of these glyphosate-resistant weed biotypes have been managed with other herbicides and cultural practices.

"Growers frequently use glyphosate as an important weed control tool so the appearance of a glyphosate-resistant population is an important reminder for growers to consider diversity in their weed management strategies and crop management practices," added Dr. Sikkema, a plant agriculture professor at the University of Guelph's Ridgetown Campus. "Fortunately, we have already been able to identify some options for this producer that will provide effective control in corn and wheat."

This finding is the result of research that began late in 2008 when the population was first brought to the attention of the University of Guelph researchers and Monsanto. The glyphosate-resistant population is limited to giant ragweed from a single field site. Dr. Sikkema is working directly with the affected grower on alternative strategies to manage this giant ragweed population.

As part of an ongoing collaborative research effort between the University of Guelph and Monsanto, other giant ragweed populations in southwestern Ontario are also being tested for their susceptibility to glyphosate. Results from these tests will help determine the scope of the issue and any need to adjust weed management strategies and recommendations. Dr. Sikkema advises growers to include diversity in their cropping systems. This includes a diverse crop rotation with multiple herbicide modes of action over time. Growers are advised to use appropriate rates and other herbicides in their program where possible, including existing residual herbicides, to reduce the likelihood of glyphosate resistance developing in their fields.

"There are definitely crop management practices that can increase the risk of resistant weeds developing. That is why we strongly recommend farmers scout their fields, follow sound crop rotation practices and use additional modes of action that complement the Roundup Ready system to control problem weeds and reduce the likelihood of developing resistance," said Dr. Mark Lawton, Monsanto's technology development lead for Eastern Canada.

Monsanto's current best management practices include:

• Start with a clean field by either utilizing a burn down herbicide or tillage to control weeds early.
• Use Roundup Ready technology as the foundation of a total weed management program.
• Add other herbicides or cultural practices where appropriate as part of the Roundup Ready cropping system.
• Use the right herbicide rate at the right time.
• Control weeds throughout the season and reduce the weed seed bank.
• Rotation to other Roundup Ready crops will add opportunities for introduction of other modes of action.

Understanding The Difference Between Glufosinate And Glyphosate

University of Illlinois Extension Weed Specialist Aaron Hager cautions farmers to know the differences between glufosinate and glyphosate.

When glyphosate-resistant soybean came on the market a few years ago, many believed it was unlikely that another herbicide or herbicide-resistant crop would be needed again, Hager said. However, over time, farmers saw more and more glyphosate-resistant weed species popping up but no new herbicide active ingredients coming into the marketplace to control them.

"Resistance evolves in weeds through repeated applications of the same type of herbicide," Hager said. "The once-perceived invincibility of glyphosate has been tempered by the realities imposed by the diversity of our Illinois cropping systems. New weed management practices are needed to manage the consequences of long-term weed control."

One new herbicide-resistant variety, glufosinate-resistant soybean, became commercially available in 2009. Glufosinate, another non-selective herbicide, is sold under the trade name Ignite.

And while glyphosate and glufosinate may sound alike and share certain similarities as they provide broad-spectrum weed control, lack soil-residual activity, and require herbicide-resistant crops for in-crop applications, they should not be used interchangeably.

"Significant differences exist between these two popular herbicides that require deeper understanding of how each one works," Hager said. "For example, in 2010 you would not want to spray glyphosate on glufosinate-resistant soybean, or glufosinate on glyphosate-resistant soybean."

Glufosinate inhibits a plant enzyme involved in the early steps of nitrogen assimilation. Its target site is completely different than glyphosate's. Because of this, glufosinate can control glyphosate-resistant weed populations such as waterhemp and marestail.

While their spectrum of control is comparable for several weed species, glufosinate tends to be more effective on annual broadleaf weeds than annual grasses, while glyphosate is more effective on grasses.

Glufosinate is a "contact" herbicide, in contrast to glyphosate being extensively translocated within the plant. Hager encourages farmers to utilize application parameters that provide for the best coverage of target weeds and consider environmental conditions that optimize glufosinate's performance.

For example, glufosinate performs better in bright sunshine and warm air temperatures. Due to its limited translocation, glufosinate should be applied when annual weeds are 6 inches tall or less.

"We can control large weeds with glyphosate," Hager said. "But we have to manage weeds with glufosinate. We need to think differently about how we apply it. Farmers may want to include soil-residual herbicides or spray glufosinate twice — early when the weeds are smaller because it needs contact with the whole plant and a second time due to waterhemp's late emergence."

Bayer Announces Ignite Herbicide Price Cuts - More LibertyLink Acreage For 2010?

In a move that could well encourage more growers to plant LibertyLink crops, Bayer today announced that it is cutting the price of Ignite, the broad spectrum herbicide applied on those varieties. Here's part of a press release from Bayer:

Bayer CropScience announced today a price cut on Ignite herbicide in time for the 2010 season. The company is reducing its price for the herbicide in the range of 20 percent — effective immediately.

“The use of Ignite herbicide and the LibertyLink trait is fundamental in preserving the utility of glyphosate and glyphosate-tolerant crops as a viable crop production tool,” said Andy Hurst, Bayer CropScience product manager for Ignite herbicide and LibertyLink.

“Growers want to avoid weed resistance yet maintain simple and efficient weed management,” Hurst explained. “The launch of LibertyLink in soybeans and new FiberMax® cotton varieties with the LibertyLink trait enable effective weed management combined with high yields.”

In corn, growers can take advantage of their Herculex®, SmartStax, and Agrisure hybrids with corn borer protection by choosing the cost-effective option of Ignite on those acres this year.

Additionally, Ignite is an effective burndown tool prior to emergence of glyphosate-tolerant crops. Ignite can be applied as a burndown treatment prior to planting or emergence of cotton, soybean, canola, corn or sugarbeet.

Bayer CropScience is fully committed to supplying Ignite herbicide to meet the demand as crop acres with the LibertyLink trait ramp up, said Hurst.

“The company has invested more than $150 million in expansion of Ignite manufacturing capacity to accommodate expected demand,” Hurst said. “In addition to seed and crop protection portfolios, Bayer CropScience will lead in the development and commercialization of next-generation herbicide-tolerant traits and other traits of value in soybeans, cotton, corn, canola and other crops.”