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Weed Wisdom – October 22, 2018


Herbicide-resistant weed diagnostic testing – collect samples now

By Dr. Charles Geddes

The incidence of herbicide-resistant weed biotypes in western Canada is on the rise. Recent surveys indicate that about 57% of fields in Saskatchewan, and 68% of fields in Manitoba, contain a herbicide-resistant weed biotype. These numbers are up compared with Saskatchewan and Manitoba reports of 31% and 48% of fields in 2008/2009 and 10% and 32% of fields in 2002/2003. Recent results for Alberta have yet to be published, but the incidence of herbicide-resistance has undoubtedly increased here as well.

There is no question that the rise in herbicide-resistant weeds is due to repeated use of herbicides with the same site-of-action, and also a lack of diversity in many weed management programs. However, even farmers with a diligent weed management program are susceptible to encroachment from neighboring farms. Here lies the problem with “the tragedy of the commons” (a concept introduced in 1833, but resurrected in 1968 by ecologist and philosopher Garret Hardin). However, we all have a social responsibility to be good stewards of the land, and a collective approach to management of herbicide-resistance is warranted to slow the spread of these wicked pests. I digress…

As with any health condition, early diagnosis is best; it just so happens that herbicide-resistant weeds are a health condition of the land. To help growers identify which herbicide-resistant weeds are present in their fields, the Weed Ecology and Cropping System research program based out of AAFC-Lethbridge is offering to assist with screening weed biotypes for unique herbicide-resistance traits. This service is currently free-of-charge, and it is recommended that farmers take advantage of this program. In 2018, we are offering testing for:

  • Glyphosate (group 9)-resistant kochia
  • Auxinic herbicide (group 4)-resistant kochia
  • Other weeds with suspected cases of unique resistance (by province) not identified on page 50 of the 2018 Saskatchewan Guide to Crop Protection 

If you are interested in taking advantage of this service, please contact Dr. Charles Geddes (Phone: 403-359-6967; E-mail:; Twitter: @charlesmgeddes) at AAFC-Lethbridge. Click here for further information and for the sample submission form. Samples can also be submitted via the Saskatchewan Crop Protection Lab 


Current testing procedures require mature, viable weeds seeds. Now is the time to collect seed from weeds with suspected herbicide-resistance traits and get those populations tested.