Management of glyphosate resistant and new, invading weeds in Ontario

Principal Investigator: Peter Sikkema

Scientific Summary:

Disclaimer: The information presented here does not constitute a recommendation by the researcher or Grain Farmers of Ontario. Always read and follow the pesticide label before use. Always ensure that you have the most current label.

One of the greatest challenges facing Ontario farmers is the control of glyphosate resistant (GR) and the control new, invasive weeds for which there is little or no efficacy data for registered herbicides. These new weeds are a result of: a) the widespread adoption of Roundup Ready crops and the associated dramatic increase in the use of glyphosate for weed control, b) the increased adoption of no-till production systems and therefore the increased use of glyphosate as a burndown, b) reduced use of herbicides with an alternate mode-of-action, and d) greater movement of farm machinery and produce which facilitates the rapid movement of weeds. There are five GR weed species in Canada: giant ragweed (Ambrosia trifida) [Ontario], Canada fleabane (Conyza canadensis) [Ontario], common ragweed (Ambrosia artemisiifolia) [Ontario], kochia (Kochia scoparia ) [Alberta and Saskatchewan], and waterhemp (Amaranthus tuberculatus) [Ontario]. In studies conducted on Ontario farms yield losses in soybean due to Canada fleabane, giant ragweed and common ragweed competition was as high as 99, 96 and 92%, respectively.

This research, and the corresponding knowledge transfer, has increased the awareness of glyphosate resistant and invading weeds problem for Ontario farmers. This research program strives to develop cost effective control strategies for producers who have these weed biotypes on their farms and help reduce the spread of glyphosate resistant and invading weeds in Ontario.

The results from this project on the effectiveness of herbicides and 2-pass programs to control glyphosate resistant weeds in corn, soybean and wheat have been added to the Pest Manager app and have been used to provided updated information to OMAFRA Publication 75, Guide to Weed Control.

Results of surveys on the distribution of glyphosate resistant weeds in Ontario

  • Glyphosate resistant (GR) common ragweed has been confirmed in Essex county.
  • GR waterhemp has been confirmed in Essex, Kent and Lambton Counties. Of great concern is that 3-way multiple resistance to Group 2, 5 and 9 has been found on Essex and Lambton counties.
  • GR giant ragweed has been confirmed in Essex, Kent, Lambton, Elgin, Middlesex and Huron counties
  • GR Canada fleabane has been confirmed in 28 counties in Ontario from Essex county in the southwest to Glengarry county on the Quebec border. Of great concern is that in 22 counties there is multiple 2-way resistance to Group 2 and 9.

Project Related Publications

Carolyn King. Top Crop Manager magazine. November 7, 2014. Glyphosate-resistant weeds. https://www.topcropmanager.com/glyphosate-resistant-weeds-16369/

Carolyn King. Top Crop Manager magazine. March 28, 2017. Managing glyphosate-resistant waterhemp. https://www.topcropmanager.com/managing-glyphosate-resistant-waterhemp-20022/

a) Common ragweed

 Van Wely, Annemarie, C., Nader Soltani, Darren E. Robinson, David C. Hooker. Mark B. Lawton and Peter H. Sikkema. 2015. Glyphosate and acetolactate synthase resistant common ragweed (Ambrosia artemisiifolia L.) in southwestern Ontario. Canadian J. of Plant Science. 95:335-338.

b) Giant ragweed

Vink, Joseph P., Nader Soltani, Francois J. Tardif, Darren E. Robinson, Mark B. Lawton and Peter H. Sikkema. 2012. Occurrence and distribution of glyphosate-resistant giant ragweed (Ambrosia trifida L.) in southwestern Ontario. Can J. Plant Sci. 92: 533-539.

Follings, Joanna, Nader Soltani, Darren E. Robinson, Francois J. Tardif, Mark B. Lawton and Peter H. Sikkema. 2013. Distribution of glyphosate and cloransulam -resistant giant ragweed (Ambroisa trifida L.) populations in southern Ontario. Agricultural Sciences. 4(10): 570-576. 

c) Canada fleabane

Budd, Christopher M, Nader Soltani, Darren E. Robinson, David C. Hooker, Robert T. Miller and Peter H. Sikkema. 2018. Distribution of glyphosate and cloransulam-methyl resistant Canada fleabane [Conyza canadensis (L.) Cronq.] in Ontario. Canadian Journal of Plant Science 98:492-497.

Byker, Holly, P., Nader Soltani, Darren E. Robinson, Francois J. Tardif, Mark B. Lawton and Peter H. Sikkema. 2013. Occurence of glyphosate and cloransulam resistant Canada fleabane (Conyza canadensis L.) in Ontario. Can. J. Plant Sci. 93: 851-855.

d) Waterhemp

Schryver, Mike, Nader Soltani, David C. Hooker, Darren E. Robinson, Patrick J. Tranel and Peter H. Sikkema. 2017. Glyphosate resistant waterhemp (Amaranthus tuberculatus var. rudis) in Ontario, Canada. Canadian Journal of Plant Science 97:1057-1067.