Field Scouting Will Help Prevent Glyphosate Resistance

A message from the Ontario Weed Committee

Quick Facts On Glyphosate Resistance:

Fact: There has been rapid adoption of glyphosate-tolerant technology in Ontario. This has led to an increase in the number of acres sprayed with glyphosate.

Fact: Repeated use of any one herbicide will eventually select for herbicide resistant weeds.

Crop Scouting is Essential!

Weed control with glyphosate tolerant crops has been marketed as simple and easy. Unfortunately, simplicity can often lead to complacency. Atrazine was extensively used in the 1970's because it was simple and no other herbicide matched its effectiveness. Crop scouting became a low priority because atrazine would control whatever was in the field. As weed shifts and resistance to atrazine developed, its effectiveness as a "control all" herbicide diminished.

Ontario growers are in a similar position today, glyphosate is effective on a number of weeds and can control them at various stages. It is because of those traits that crop scouting becomes more critical for ensuring economic success.

• Scouting maximizes the value of your post-emergent weed control costs: By identifying the weed spectrum within a field, a herbicide program can be tailored (with either a specific product or rate) to fit the given spectrum.
• Scouting minimizes yield losses from weeds: Determining when weeds have emerged with the crop and initiating control when weeds are most susceptible will ensure that yield loss is minimized.
• Scouting identifies subtle changes in weed populations before they become a huge problem: By making note of the weed spectrum, intensity and time of emergence from year to year, small changes in weed population dynamics can be addressed before they become an uncontrollable problem.

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If you see unusual weed escapes report them!

Be on the lookout for the following symptoms in your field:

• A weed species that should have been controlled but is healthy while other susceptible species have been controlled.
• Poor control of a susceptible weed when the herbicide was used according to the product label.

Stop a potential problem from getting worse. If you see any weed escapes whereby a good explanation for their lack of control does not exist, report them by calling:

1-877-424-1300

OMAFRA Agricultural Information Contact Centre

Take advantage of this toll-free number. The University of Guelph will test suspicious weed escapes for resistance free of charge. Any information obtained from this service is confidential and will allow weed researchers to develop control options for resistant weed populations.

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