Wheat School: Timing a PGR application in winter wheat

Syngenta Canada agronomist Marijke Vanderlaan

Ontario’s winter wheat crop has come through the winter in good condition and is packed with yield potential.

But there is concern: a crop with big stem- and head-counts carries a much higher risk of lodging. To reduce this risk, growers will be looking to apply a plant growth regulator (PGR) to help the crop stand and yield.

On this episode of the RealAgriculture Wheat School, host Bernard Tobin is joined by Syngenta Canada agronomist Marijke Vanderlaan to review best practices for PGR application. She notes that the sweet spot for optimum growth regulator application is growth stage 30 to 32.

The field in this video is at growth stage 30 and is reflective of most winter wheat in the province. Vanderlaan notes that it takes the wheat crop about 100 GDDs to move from one growth stage to the next. In this scenario, that means the optimum application window would last about two weeks. But with late-April temperatures running below normal, the optimal window will likely last longer. (Story continues after the video.)

Vanderlaan adds that Moddus, Syngenta’s PGR product, can be applied up to growth stage 37. She notes that in 2021, another cool spring, the company did observe excellent protection from the product even when it was applied at a later stage.

In the video, Vanderlaan also addresses the question: how cold is too cold to apply a PGR? She says there are a couple of scenarios to consider. When there’s only a PGR in the spray tank, she says Syngenta is comfortable with growers spraying the product when the temperature goes “down to zero degrees at night, or as long as it’s above freezing at night and about five degrees plus, during the day.”

The rules change, however, when growers are tank-mixing a PGR with other products such as a herbicide and/or a fungicide. Here, growers need to follow the rule of three. In this case “we want temperatures at night to be above three degrees Celsius —the day before, the day of, and the day after that application,” says Vanderlaan.

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