Experts explore options for new weed controls

Mustard growers shouldn’t expect a silver bullet to help them fight weeds, says a weed biologist.

However, ongoing work should provide new additions to a limited list of registered herbicides for the crop.

“There are fairly limited options because the companies really don’t try to develop a product for a small crop like mustard. Even canola is pretty small potatoes,” said Eric Johnson with Agriculture Canada.

“They’re looking at wheat or rice or corn or soybean. If it happens to work on these other crops, then it gets registered, usually through minor use.”

Research plots in Saskatoon are testing carinata and oriental, brown and yellow mustard performance following an application of the Group 14 herbicide Authority.

The herbicide, whose active ingredient is sulfentrazone, is normally used on sunflowers, peas, chickpeas and flax.

Johnson said previous work had identified Authority as weak on wild mustard. Carinata is the most sensitive of the commercial mustards to the herbicide, while yellow varieties are the most tolerant.

He expects that a registration for yellow mustard will come, but it remains more than a year away. Until then, applications remain illegal, except in his developmental plots.

Options for growers include Edge and Muster.

In yellow mustard, Johnson is looking at a low-rate, pre-seeding springtime application of Authority, similar to the herbicide’s chickpea registration. Injury from fall applications was too high, he added.

Applications would target broadleaf weeds, including kochia, wild buckwheat, red root pigweed and lambs quarters. Any possible registration for other species of mustard would come later after researchers collect more data and fine tune application rates.

“We were suggesting the lower rate for mustard, knowing that even a lower rate will control kochia. The problem is when you try to go to a lower rate with registration, PMRA (Pesticide Management Regulatory Agency) says, ‘why now? What’s changed? Why didn’t you have that rate registered to begin with?’ ” said Johnson.

The current label for Authority warns against applications in soil with an organic matter content greater than six percent. Applications would also prevent lentil crops from being seeded for two years.

Johnson said researchers are also looking at possibilities with Group 4 herbicides such as dicamba and a combination of fluroxypyr and 2,4-D (Attain), which could be stacked with Group 2 resistant traits.

“If you look at corn and canola, about half of the yield increases have been due to breeding and half due to agronomy. I expect we’ll come up with a similar situation in the future,” said Johnson.

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