Rsearchers continue field surveys to track spread of glyphosate-resistant weeds

Weed scientists at the University of Guelph, working in conjunction with Monsanto Canada, continue to monitor the spread of two glyphosate-resistant weed species in Ontario and offer recommendations to farmers to help manage these hard to control weeds.

New information collected from field surveys, conducted by Dr. Peter Sikkema and Dr. Francois Tardif from the Department of Plant Agriculture at the University of Guelph over the last several months, indicates the total number of sites with glyphosate-resistant Canada fleabane now stands at 77. The glyphosate resistance was found in four different counties - Essex, Lambton, Kent, and Elgin. Glyphosate-resistant Canada fleabane was initially confirmed at just eight sites in Essex County from seed collections made in 2010.

Glyphosate-resistant giant ragweed has been confirmed at 48 locations in Ontario - 46 of the locations are in Essex County with a single confirmed site in Kent and Lambton counties. Glyphosate-resistant giant ragweed was first confirmed in the region in 2008.

"It is important to document the geographic distribution of glyphosate-resistant weed species in the region because it helps to understand the scope of the problem and that is critical information for farmers," said Dr. Sikkema. "We also want to get the word out to farmers so they can take steps immediately to limit the spread and lessen the likelihood of resistance developing or spreading to additional regions."

Sikkema said he was not surprised by the presence of the glyphosate-resistant Canada fleabane in Ontario because it is prevalent in 20 U.S. states and has been moving north for the past decade. He was surprised, however, by how quickly Canada fleabane has moved and the level of density of the weeds that is showing up in some fields.
Canada fleabane produces a large number of small seeds that can move easily under field conditions.

One of the key strategies for managing glyphosate-resistant weeds is education, information and communication. There are weed management solutions in place to control glyphosate-resistant weeds and Monsanto Canada has elevated its communication to ensure farmers are aware and prepared to responsibly and sustainably deal with control of glyphosate-resistant Canada fleabane and glyphosate-resistant giant ragweed.

"We have a concerted communications program across the region to ensure farmers first understand these weeds are present in their communities and second, and probably more important, ensure they understand the steps they can take to limit the spread and the options available to them for control," said Dr. Mark Lawton, technology development lead with Monsanto in Eastern Canada.

Lawton says several effective solutions are available to those farmers who have been impacted. For glyphosate-resistant giant ragweed, products registered for use in pre-plant/pre-emergent burndown such as FirstRate in soybeans and Marksman or Banvel II in corn are good options. As well, there are registered options for in-crop control in both corn (Banvel II) and soybeans (FirstRate). For glyphosate resistant Canada fleabane, Eragon or Amitrol are registered for use pre-plant/pre-emergent in soybeans, and Eragon or Banvel II are registered for corn. Where in crop applications are required, FirstRate is registered for use in soybeans and Banvel II in corn.

"I think the awareness and understanding of glyphosate-resistant weeds in Ontario has definitely improved among farmers and our key message to them is that these weed species are controllable with good agronomic practices such as using tank mixes and/or other cultural weed control methods," said Dr. Lawton. "And in all cases, we continue to recommend that farmers use the right rate of glyphosate for the right sized weed at the right time, as well as any additional weed control tools that may be necessary for the weed spectrum on their farm."

One of the new tools Monsanto has made available to farmers looking to assess the likelihood of glyphosate resistance developing on their farm is a new online web-based resource at www.weedtool.com. Introduced in 2010, the site offers farmers a list of best practices for weed management; an extensive amount of solid, effective agronomic advice for control of glyphosate-resistant weeds; and a short 10-question survey that generates a report for the farmer about where their farm sits in terms of reducing the likelihood of glyphosate-resistant weeds developing.

"It is pretty critical that farmers get past a glyphosate-only strategy for their weed management in Roundup Ready crops and that is something we have been very proactive about communicating and explaining to farmers," said Dr. Lawton. "We have been successful in controlling these weeds in other regions of the world such as Brazil and the U.S. so with continued research and collaboration with academics and testing of alternative approaches we think we can be successful here in Canada. The key is to tackle the issue before it becomes a problem."

Sikkema and his colleagues at the University of Guelph have also been active with respect to testing a number of new options for managing both weed species in soybeans and says managing them early prior to planting is the most effective method of control.

"Pre-plant application of Eragon, Amitrol, Sencor, FirstRate or Broadstrike RC has worked well on glyphosate-resistant Canada fleabane in soybean. Eragon, Amitrol, Lorox and 2,4-D have been effective on giant ragweed prior to planting soybeans," says Dr. Sikkema. "We have also tested the new dicamba tolerant soybeans system for a couple of years and the application of dicamba prior to planting soybeans, or applying in-crop has been very effective on both giant ragweed and Canada fleabane populations resistant to glyphosate."

Although further testing and regulatory submission and approvals will take time, Monsanto Canada is hopeful that a commercial product will be available to Ontario soybean growers for the 2014 growing season.

"Our existing recommendations around sustainable weed management solutions in soybeans support the use of multiple modes of action as part of an integrated weed management strategy so the future commercial introduction of dicamba-tolerant soybeans definitely supports this strategy," explains Dr. Lawton.

The collaborative research effort on distribution and management of these two glyphosate-resistant weeds continues with Monsanto and the University of Guelph.

"We have learned a lot in a short period of time through this research and have worked hard to communicate our findings and results as we analyzed the research data," says Dr. Lawton. "We remain committed to continue the research studies to ensure farmers have the weed management tools in place to be successful for many years to come."

Monsanto Canada is headquartered in Winnipeg, Manitoba. Monsanto Company is an agricultural company and a leading global provider of technology focused on enabling small-holder and large-scale farmers produce more from their land, while conserving more of the world's natural resources such as water and energy.