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August 3, 2011

Note regarding preharvest use of Roundup Weathermax for tame mustard for export

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.

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 following MRLs pertain to glyphosate MRLs in tame mustard

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