Pest Patrol: Xtend soybeans, spray drift and controlling glyphosate-resistant fleabane

#PestPatrol with Mike Cowbrough, OMAFRA

I want to plant Roundup Ready 2 Xtend soybeans this season to control my glyphosate-resistant Canada fleabane. But I keep hearing about the increased risk of drift with the dicamba-based herbicides. Is this fear mongering, or do I need to pay special attention when applying herbicides containing dicamba?

We can learn a lot about the risks of dicamba drift from our neighbours to the south. This past year in the United States, some farmers planted Roundup Ready 2 Xtend cotton and soybean cultivars. Unfortunately the “low drift” dicamba herbicides that were intended for these cultivars had not yet been approved. Presumably, out of desperation to control weed species like palmer amaranth (which is resistant to multiple herbicides), some farmers applied older, more drift-prone formulations of dicamba. This was an off-label application, and given the number of drift-related dicamba complaints, it was applied badly.

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During the 2016 season, the number of reported dicamba-related incidents increased substantially. In Missouri alone, 94 per cent of all pesticide-related complaints involved dicamba, where in years previous there were almost none. Fortunately in Ontario, the approved “low-drift” dicamba products (currently Xtendimax, Engenia and Roundup Xtend) are available for use on Roundup Ready 2 Xtend soybeans for 2017. These new products are less expensive than the older formulations of dicamba herbicides, so there is no logical reason why a grower should use anything but the approved herbicides. Since dicamba can cause extremely visual crop injury (Figure 1 at top) with yield losses to sensitive crops like non-resistant soybean at doses as low as 0.125 per cent of the normal field rate (Soltani et al. 2016), applicators must implement specific requirements to reduce the risk of off-target drift.

I reached out to our ministry’s application technology specialist Jason Deveau to glean some tips on how to manage this new technology safely. Deveau worked with representatives from Monsanto and BASF to summarize critical sprayer application requirements when applying the new formulations/chemistries to Roundup Ready Xtend soybeans (Figure 2 below).

Figure 2. Labelled sprayer application requirements for the Roundup Ready Xtend Crop System. Courtesy of
photo: Supplied

This article is your starting point. There are plenty of tips for pesticide applicators at

If you search “drift” on the site, there are several excellent tools and resources to assist you in preparing for the 2017 season.

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

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