Chemfallow best management practices

Blair McClinton, P.Ag.
May 10, 2017
By Blair McClinton, P.Ag.
With the confirmation of glyphosate-resistant (Group 9) kochia across the Prairies, a renewed focus on best chemfallow management practices is needed.


  1. Scout fields and apply herbicides at the optimum timing for the best weed control. Weed control is generally best when weeds are small and actively growing.
  2. Apply glyphosate with a tank-mix partner that is effective on all weeds and herbicide-resistant biotypes. For example, all kochia on the Prairies is considered to be resistant to Group 2 herbicides. Tank-mixing glyphosate with a Group 2 herbicide will not control kochia that is also resistant to glyphosate.
  3. Group 2 + 4-resistant kochia has been confirmed on the Prairies. Use “effective” tank mix-partners with multiple modes of action to delay the development of herbicide resistance. Use herbicides with multiple modes of action from different groups; each mode of action should be effective on the target weed.
  4. Diversify your chemfallow tank-mixes (groups) throughout the growing season.
  5. Use full rates of herbicides. Reduced rates may help select for herbicide resistance.
  6. Note re-cropping restrictions that may prevent planned crop rotations in the following year.
  7. Consider using tillage that conserves crop residues in combination with herbicides. Wide-blade cultivators that leave the majority of the stubble standing are a good choice because they help preserve moisture and protect the soil from erosion.
  8. Scout after application to assess weed control and possible herbicide resistance. Control weed escapes before they go to seed. Consider physical destruction utilizing tillage of patches, mowing, or hand trimming. Re-application of the same group of herbicides on weed escapes will put further selection pressure on weed escapes and could speed the development of herbicide resistance.
  9. Plan ahead for pre-seed burndown so you aren’t using the same modes of action or compromising cropping restrictions.
  10. Change things up. What worked well yesterday and today may not work tomorrow. Change up your crop rotations, application timings and seeding dates. If a chemfallow program worked this past year, try something different in 2017 to keep weeds off-balance.
There are no re-cropping restrictions for the following year with any of the products listed when used according to the chemfallow label.

Chart developed by Blair McClinton, P.Ag., with information compiled from the Saskatchewan/Manitoba Guide to Crop Protection and herbicide labels.

Follow the information on product labels if there are any discrepancies with information in this table.

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