Be cautious with your pre-harvest herbicide applications

Pre-harvest herbicide applications are becoming more widely used by grain producers. However producers should be aware that outside scrutiny of these practices from buyers concerned about herbicide residues above maximum residue limits is increasing. As a result, producers must have a clear strategy of whether they are trying to achieve preharvest weed control or crop desiccation.

Pre-harvest weed control operations are aimed at the control of perennial weeds in a given crop. This usually involves systemic herbicides and is an appropriate application provided label recommendations for timing or staging is followed. This staging for many crops is an application when the seed moisture content of the crop is 30 % or lower indicating that the crop is physiologically mature. Herbicides applied prior to achieving this moisture content can result in herbicide residue amounts exceeding the maximum residue limit.

Crop desiccants are those products that are typically used for rapid crop drydown to aid in harvest. In most cases these products will also dry down the weed materials but will not provide control of perennial weeds.

Using pre-harvest herbicides responsibly is our best strategy to ensure access to markets that we wish to export to. To ensure that this is maintained producers should:

- Use products as per label instructions for timing, staging and rates.

- Adhere to preharvest intervals as indicated on the label

- Consult with their grain buyers to ensure that planned destination countries have established maximum residue limits in place.

For more information on responsible herbicide use and updates on which herbicide/crop combinations may be of concern, consult the Keep it Clean website at www.keepingitclean.ca .

John Ippolito, Crops Extension Specialist, Saskatchewan Ministry of Agriculture