GLYPHOSATE RESISTANCE.... THINKING AHEAD
by Mike Cowbrough, OMAF

Canada fleabane

In the United States, glyphosate resistant Canada Fleabane has infested literally hundreds of thousands of acres across 10 different states. If an Ontario grower were to encounter this resistant weed tomorrow, there would be cost effective solutions available for them to use (see Table 1). However, this type of information is only possible if growers follow Step #6 in the responsible glyphosate use guidelines (see sidebar), as this allows our great team of weed scientists to explore practical solutions. Bottom Line: First Rate, Amitrol 240, Classic and Broadstrike Dual II Magnum all provided acceptable levels of Canada Fleabane control, and would be suitable options in soybean as a tank-mix partner with glyphosate (where registered) or as an alternative to glyphosate.

RESPONSIBLE GLYPHOSATE USE IN FIELD CROPS

Glyphosate and Roundup Ready crops are valuable weed management tools, however:

  • The risk of glyphosate resistant weeds will increase if glyphosate is managed improperly.
  • In the United States, there are populations of Common Ragweed and Canada Fleabane resistant to glyphosate.
  • No new herbicides are currently being developed to replace glyphosate.

There is a tremendous opportunity for Ontario growers to become leaders in the stewardship of glyphosate.The Ontario Weed Committee has devised the following guidelines for responsible glyphosate use that is intended to minimize the risk of glyphosate resistant weeds.

1) Know What You Have

Scout fields for weed species and density. If this is beyond your area of interest or expertise, then hire a certified crop adviser to do so for you.

2) Develop A Plan

Once your field has been scouted and you know what weed species you have, sit down with your certified crop adviser and develop a long-term management plan to address your weed spectrum.

Your Plan Should Consider:
"THE SEVEN STEPS OF RESPONSIBLE GLYPHOSATE USE"

Step I: Use "Roundup Ready" technology in fields where it will have the greatest economic benefit.
Step 2: Rotate "Roundup Ready" crops with conventional or other herbicide tolerant crops as well as rotate herbicides with different modes of action.
Step 3: Always use the full labeled rate of glyphosate.
Step 4: Tank-mix glyphosate with residual herbicides where appropriate.
Step 5: Use cultivation where appropriate.
Step 6: Scout for and report any suspected glyphosate-resistant weeds to 1-877-424-1300.
Step 7: Control and prevent the spread of weed escapes.
For more information on herbicide resistance visit: www.plant.uoguelph.ca/resistant-weeds