Soybean School: Controlling Canada fleabane with cereal rye

Photo: Warren Schneckenburger

From microwave ovens, to X-rays, and even potato chips, many important discoveries have been stumbled upon by accident.

The same may to be true when it comes to weed control and the continuing fight to control glyphosate-resistant Canada fleabane. On this episode of RealAgriculture’s Soybean School, Mike Cowbrough, Ontario Ministry of Agriculture, Food and Rural Affairs weed specialist, shares how a farmer accidentally seeding a cereal rye cover crop through a herbicide trial alerted researchers to rye’s ability control fleabane.

In 2015, the year following the accidental cover crop seeding, significantly less Canada fleabane appeared in the trial area where the cereal rye had been seeded. On this episode, Cowbrough shares how the incident spawned a set of experiments by University of Guelph graduate student Ted Vanhie and what the research reveals about the power of cereal rye to control Canada fleabane.

The results are impressive. In 2018, cereal rye reduced biomass of Canada fleabane by 96 per cent and in 2019 it was reduced by 94 per cent. Cowbrough explains that Vanhie’s research indicates that cereal rye’s weed control power is linked to the high level of specific allelopathic chemicals present in the plant’s roots and shoots. (Story continues after the video.)

Cowbrough does say, however, that when you have high population densities of weeds (fleabane populations can reach up to four million plants per acre), the remaining four to six per cent can still be a considerable amount of fleabane to control. He also notes a second significant impact cereal rye has on fleabane — it can reduce individual fleabane plant height by 61 to 88 per cent.

With that type of impact, Cowbrough believes that cereal rye could function as another mode of action to control the weed. When its effects — fewer and smaller fleabane — are combined with other effective herbicide modes of action, control of the weed could be enhanced significantly.

The challenge for growers who follow corn with soybean in their rotation is to fall seed and establish a cereal rye cover crop in a late harvested corn crop. But Cowbrough believes farmers are up to that challenge as many innovators are already finding ways to use high-clearance seeders to effectively establish cereal rye in corn.

Click here for more Soybean School episodes.

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