Key Learnings From 2017 in an Ongoing Effort to Manage Glyphosate Resistant Canada Fleabane

When learning from agronomists and farmers about their experience with managing glyphosate resistant Canada fleabane, there is consensus that multiple strategies are needed and that simply tank-mixing another mode of action will not be a good long-term approach. Since 2016 we have evaluated different management tactics for Canada fleabane. We have observed the following at our Oxford and Norfolk county field locations:

  1. Tillage needs to be done multiple times (both fall and spring) to eliminate the majority of plants. Although a single tillage pass to a high population environment did result in fewer plants, the survivors were often 10-15 cm taller and branched (Figure 1) most likely because they did not have to compete with plants removed by the single tillage pass. These larger plants were more difficult to control with herbicides.
  2. Fall applied herbicides did not provide acceptable Canada fleabane control because a new flush of seedling plants germinated in the spring. Spring applied herbicides were much more effective with both Eragon LQ (Figure 2) and dicamba (Figure 3) providing the best level of control, however the lowest labelled rate of both herbicides failed to deliver acceptable control.
  3. There was no Canada fleabane anywhere cereal rye was planted in the fall (Figure 4), regardless of herbicide or tillage treatment. This is an exciting observation that will require follow-up to understand how a cereal rye cover crop should be managed to optimize control of Canada fleabane.

Figure 1. Canada fleabane plants the following spring after surviving fall tillage. Note the plants have multiple branches at the base and were often 10-15 cm taller than plants not exposed to fall tillage.

Figure 1. Canada fleabane plants the following spring after surviving fall tillage. Note the plants have multiple branches at the base and were often 10-15 cm taller than plants not exposed to fall tillage.

Figure 2. Canada fleabane control with Eragon LQ at 60 mL/ac compared to the un-sprayed control. The lower 30 mL/ac rate failed to deliver acceptable control at the one field location.

Figure 2. Canada fleabane control with Eragon LQ at 60 mL/ac compared to the un-sprayed control. The lower 30 mL/ac rate failed to deliver acceptable control at the one field location.

Figure 3. Canada fleabane control with the 400 mL/ac rate of Engenia (dicamba) compared to the un-sprayed control. The lower 200 mL/ac rate failed to deliver acceptable control at the one field location.

Figure 3. Canada fleabane control with the 400 mL/ac rate of Engenia (dicamba) compared to the un-sprayed control. The lower 200 mL/ac rate failed to deliver acceptable control at the one field location.

Figure 4. Fall planted cereal rye was very effective at inhibiting the germination of Canada fleabane seedlings (left) compared to where it wasn't planted (right).

Figure 4. Fall planted cereal rye was very effective at inhibiting the germination of Canada fleabane seedlings (left) compared to where it was not planted (right).


For more information:
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E-mail: ag.info.omafra@ontario.ca