New Herbicide MRL Issue in Mustard

VANCOUVER - Aug 3/11 - SNS -- Mustard seed growers need to be careful about whether and how they use Roundup Weathermax now that it has been registered for use as a desiccant in the crop.

At the moment, the European Union is the only export destination where the maximum residue limit (MRL) for glyphosate would make it possible for farmers to safely use Roundup Weathermax.

If the mustard seed is destined for the United States or any other part of the world, using the herbicide at the recommended level will still result in residue levels which exceed the tolerances for those countries.

No MRL Means Zero Residues is Safe Choice

The Saskatchewan Mustard Development Commission says, "Growers should be aware that not all jurisdictions have set maximum residue limits (MRLs) to levels that would accommodate the glyphosate level that would arise out of preharvest use of glyphosate in mustard.

"Some countries have relatively high allowable levels of glyphosate in tame mustard seed and others have no MRL set. 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.

"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."

The MRL for the European Union is 10 parts per million. It is 0.1 parts per million in the United States, Mexico and Australia. There is no MRL in Japan or Korea or countries which use the Codex standard, such as India. If there is no MRL, zero residues is the wisest choice.

Timing Affects Residue Levels

The Saskatchewan Mustard Development Commission added, "Preharvest applications of Roundup Weathermax have been registered under the minor use system in Canada. This use is permissible for Canadian growers and it consists of applying 0.67 L/acre of the 540 g/L formulation of Roundup Weathermax at a time when pods of the mustard plant are green to yellow and seed is yellow to brown.

"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."