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Pest Patrol: Control of Canada fleabane

#PestPatrol with Mike Cowbrough, OMAFRA

Pre-plant applications of dicamba at the high rate and to emerged fleabane rosettes have provided the most effective control of glyphosate-resistant Canada fleabane (left) compared to an unsprayed strip (right) when planting Xtend soybean varieties. A followup, post-emergence application of dicamba may be necessary when new seedlings have germinated following crop emergence.

Q: Canada fleabane has shown up in various places on our farm this year. I assume it is glyphosate resistant. Do I have any other options for soybeans other than Xtend beans?

A: Yes, research conducted by the University of Guelph (Ridgetown Campus) has shown that the addition of Eragon LQ (30 ml/acre) + Sencor 75 DF (216 g/acre) + Merge (400 ml/acre) to glyphosate, and applied as a pre-plant burndown to emerged Canada fleabane has provided very consistent control. Unfortunately, if new seedlings emerge after application and when soybeans have emerged, the only option you would have to control Canada fleabane is “FirstRate” (cloransulam-methyl), and populations exist in Ontario that are resistant to that herbicide.

If planting an Xtend soybean variety, you have more pre-plant options. You could still apply the tank mix of glyphosate + Eragon LQ + Sencor + Merge or you could apply the high rate of dicamba (e.g. Engenia, Xtendimax). If new Canada fleabane seedlings emerged later, after soybean emergence, you would have the option to apply dicamba. You would have to be diligent about minimizing the risk of off-target dicamba drift; there are specific guidelines on each product label.

At the end of the day, economics will drive your decision. If non-Xtend soybean varieties out-perform any of the Xtend varieties that you’ve seen in variety trial data, then it may be more profitable for you to plant those instead. The pre-plant tank mix of glyphosate + Eragon LQ + Sencor + Merge is more expensive than the glyphosate + high-rate dicamba tank mix that you would use in an Xtend soybean system. Assuming a soybean price of around $12 per bushel, the cost difference is about 0.6 bu./ac. (of course, prices may vary).

Have a question you want answered? Hashtag #PestPatrol on Twitter to @cowbrough or email Mike at [email protected].

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