Tackling Wild Oat Resistance In Manitoba: UPL's Herbicide Layering Tools

Wild oats have long been a problem weed for most farmers in Southern Manitoba. Every year the challenge has intensified as wild oat populations show increasing resistance to herbicides-many now resistant to multiple modes of action. Because of this increasing resistance, UPL has been conducting research on wild oat resistance across the Canadian prairies for the last four years.

UPL is a global company that provides sustainable agricultural solutions and services. Best known in Canada for their herbicides, fungicides, seed treatments, and other crop protection products, UPL is committed to finding the best sustainable solutions for weed management. One of their primary goals in Western Canada is to develop effective strategies to combat wild oats, especially in fields where herbicide resistance is already suspected.

To achieve this goal, Laura Schmidt, Technical Service Specialist for UPL, designed a herbicide layering trial near Cypress River, Manitoba. The trial focused on a wheat field with suspected Group 2 wild oat resistance, evaluating various application timings and combinations of herbicide groups.

Method

The trial included 11 treatments, ranging from untreated controls to various combintions of herbicide applications. Three application timings were tested:

-          Pre-emergence
-          3-leaf stage
-          4 leaf, 2 tiller stage

Several herbicide modes of actions were tested, often in tank mixes. Pre-emergent treatments included glyphosate alone or in combination a Group 14/15.

In crop treatments featured UPL’s Batalium (containing Flucarbazone, Fluroxypyr, Bromoxynil, and MCPA), as well as other Group 1, 2, 4, 6 herbicides. Some treatments also had a second in-crop application of another group 1 and/or group 4/6.

The primary objectives were to:

-          reduce the total number of target weeds
-          slow the growth of herbicide resistance.

Results

Laura took ratings throughout the season, with the final ratings taken 50 days after application. Her ratings found anywhere from 62.5% to 90.5% wild oat control depending on the treatment. Laura emphasized the importance of considering weed pressure and environmental conditions when trying to control wild oats. Herbicide layering can be effective but physical and cultural options should also be done.

Treatments that included a pre-emergence application showed the highest levels of control, improving the efficacy of subsequent in-crop applications.  

Adding a Group 14 or 15 herbicide with the first in-crop treatment (especially when paired with a Group 2) further boosted performance. Even in fields suspected of flucarbazone resistance, Batalium still contributed to effective control, particularly when followed by a second application off a Group 1 herbicide. This strategy acted as a rescue spray and proved to be useful in situations of high weed population pressure and where weather caused late weed flushes, or if the dry conditions early in the summer compromised the first application herbicide activity.

Conclusions & Recommendations

The trial reinforced several important points for wild oat management:

-          Layering herbicides across multiple timings can significantly improve control.
-          Pre-emergent applications are critical for boosting the effectiveness of in-crop sprays.
-          Combining multiple modes of action is key to managing resistance and ensuring season-long control.
-          Environmental conditions and weed pressure must always be considered when designing a herbicide program.
-          Integrated management, including physical and cultural control methods, remains essential alongside chemical strategies.

Overall, UPL’s research highlights the value of a strategic, layered herbicide approach to tackling wild oats - particularly in fields already showing signs of resistance.

~Annabelle Calcott