January 25, 2013

Glyphosate Resistant Weeds – Intensifying

by Kent Fraser

Not only are glyphosate resistant weeds spreading geographically, the problem is also intensifying with multiple species now resistant on an increasing number of farms.

US farmers told us that 61.2 million acres of cropland are infested with glyphosate resistant weeds, almost doubling since 2010.

Stratus has asked thousands of US farmers about resistance, with surveys across 31 states over three years.  The trends are dramatic:

• Nearly half (49%) of all US farmers we surveyed said they have glyphosate resistant weeds on their farm in 2012, up from 34% of farmers in 2011.
• Resistance is still worst in the south.  For example, 92% of growers in Georgia said they have glyphosate resistant weeds.
• But the mid-south and mid-west states are catching up.  From 2011 to 2012 the acres with resistance almost doubled in Nebraska, Iowa and Indiana.
• It’s spreading at a faster pace each year:  total resistant acres increased by 25% in 2011 and 51% in 2012.
• And the problem is getting more complicated.  More and more farms have at least two resistant species on their farm.   In 2010 that was just 12% of farms, but two short years later 27% had more than one.
• Marestail (horseweed) was the weed most often reported with glyphosate resistance, followed by Palmer amaranth (pigweed).  Another half dozen species were tracked in the study.

The explosion of resistance has certainly heightened concern, but American farmers always respond to agronomic challenges!  Stratus is conducting a Resistance Management study to see just how U.S. farmers are adjusting their practices to deal with the problem.
Of course, weeds don’t pay attention to borders, so Stratus is also tracking resistance in Canada.
Contact us for more information on the U.S. Resistance Tracking Study, Canada Resistance Tracking Study and the upcoming Resistance Management Study.  stratus@StratusResearch.com  403-257-8906

www.stratusresearch.com/products.

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Our thanks go to those growers who participate in Stratus surveys.  Their input helps to shape agribusiness.  If you are a grower and you would like to contribute your opinions, you can sign up for on-line surveys at www.stratusag.com

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