Pre-harvest Roundup use on mustard comes with caution

A minor use has been approved for glyphosate as a pre-harvest desiccant on tame mustard crops in Canada — but not without a warning to export-minded growers.

The new minor use allows pre-harvest applications of Monsanto’s 540 gram-per-litre formulation of Roundup WeatherMax  at 0.67 litres per acre of yellow, brown or oriental mustard crops.

As the Saskatchewan Mustard Development Commission and Canadian Special Crops Association warned in a note to growers Wednesday, maximum residue limits (MRLs) haven’t yet been set in all importing countries, meaning those countries may not accept a load of mustard with glyphosate residue at the pre-harvest treatment level approved within Canada.

Furthermore, the SMDC said, “the U.S., which is a very important customer, has a relatively low MRL for glyphosate residue within mustard.”

The European Union (EU), for one, has an MRL of 10 parts per million (ppm) for glyphosate on mustard, compared to just 0.1 ppm in the U.S., Australia and Mexico.

Japan and Korea, meanwhile, have not yet set any MRL at all, the CSCA said. Nor has Codex Alimentarius, the international food standards body, whose guidelines, if any, would apply to levels acceptable in markets such as India.

“May be wise”

“For this reason, growers should consult with the exporter or processor to whom they are selling the crop before they use glyphosate on tame mustard,” the association said.

“In instances where the crop is going to be marketed primarily in countries outside the European Union, it may be wise to forego the use of glyphosate on tame mustard so that the crop is not potentially rejected due to glyphosate residues.”

As per the minor-use registration in Canada, the herbicide is to be used when the pods of the mustard plant are green to yellow and the seed is yellow to brown, the CSCA said.

“Growers should note that missing this timing (too early or too late), or application of higher rates than those that are labelled, can result in higher levels of glyphosate than are acceptable,” the association said.

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