Soybean School: Timing tillage for Canada fleabane control

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Cover crops, tillage and herbicides —they’re all tools growers can use to build an effective, integrated approach to controlling troublesome Canada fleabane.

On this episode of RealAgriculture’s Soybean School, Ontario Ministry of Agriculture, Food and Rural Affairs weed specialist Mike Cowbrough looks at the role tillage can play in controlling the weed. He notes mounting evidence of the impact a cereal rye cover crop can have on the weed, but when it comes to tillage, performance is inconsistent.

Cowbrough points to a two-year fall vertical tillage research trial conducted by University of Guelph graduate student Ted Vanhie — the same trial that identified the impact of cereal rye research. In both years of Vanhie’s study, cereal rye provided consistent results; tillage, however, did not. (Story continues after the video.)

In the first year of the study, 2018, fall vertical tillage reduced total above-ground biomass by 100 percent and this also enhanced the control achieved with spring applied herbicides, specifically 2,4-D, dicamba and Eragon LQ, says Cowbrough.

But in 2019, tillage had no effect on biomass of Canada fleabane compared to no-tillage. This result was in contrast to other studies, and it’s likely that germination patterns relative to the timing of tillage contributed to the poor performance — cooler fall temperatures and lower growing degree days accumulation meant Canada fleabane seedlings likely emerged after tillage in 2019.

These results further emphasize the need for an integrated approach. “Tillage for the purpose of killing weeds is no different than using herbicides or planting cover crops — the timing of the operation relative to the biology of the weed is very important,” says Cowbrough. “The incorporation of fall tillage, a fall-seeded cereal rye and effective spring herbicides appears to be the most fail-proof method to control Canada fleabane, because if any one tool falters, there are other ones to pick up the slack.”

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