Pest Patrol: The latest word on nipplewort in cereals

#PestPatrol with Mike Cowbrough, OMAFRA

Figure 1: The untreated control plot.

Here’s a question in my in-box. “I have a customer with a no-till rotation that has nipplewort — a lot of it. We found some pretty decent options for most crops in the rotation to clean it up before planting, but he’s got some in his wheat this year too.

“What would be our best option to take a swing at it in wheat?”

For a brief primer on nipplewort, I would refer you to the December 2014 issue of Country Guide, where I provided an overview of what we knew about managing nipplewort at the time.

The fact is, though, sometimes it takes a long time to find a good solution for a weed that is difficult to control. In the case of nipplewort infesting cereal crops, it has taken so long that if nipplewort was a person, it could legally vote.

Figure 2: Nipplewort control at six weeks after an application of Pixxaro herbicide. photo: Mike Cowbrough, OMAFRA

First off, nipplewort is not an overly common weed species. Finding fields with uniform and relatively dense stands of this weed has proven challenging, which makes it difficult to do replicated herbicide trials. For the farmers who have it, though, it does negatively affect crop production, especially in winter cereals where it typically germinates in the fall and becomes quite large by the time post-emergence herbicides are applied in the spring.

Figure 3: Nipplewort control at six weeks after an application of Infinity FX herbicide. photo: Mike Cowbrough, OMAFRA

Second, nipplewort is tolerant to a lot of herbicides. Therefore, you need to screen numerous herbicides and tank mixes in order to find promising treatments that you would want to test under field conditions.

Dr. François Tardif, Peter Smith (University of Guelph) and I started this process in 2002 and we certainly were able to identify herbicides that didn’t work.

Figure 4: Nipplewort control at six weeks after the tank-mix application of Lontrel XC + Refine SG + non-ionic surfactant. photo: Mike Cowbrough, OMAFRA

Thankfully we also found a handful of products that gave us reason for optimism; we just needed to tweak some treatments and look at them under more field sites. Finally, here in the 2020 field season, we have more confidence that one tank mix in particular, Lontrel XC + Refine SG + non-ionic surfactant, gives us the best opportunity to control nipplewort. We also discovered that some of the newer herbicides that weren’t available back in 2002, aren’t particularly effective (Table 1 below).

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

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