Canadian cereal growers can protect their investment and help to maintain market access for everyone by carefully planning and managing pre-harvest glyphosate applications. The following special considerations should be taken when applying glyphosate pre-harvest:

  • Wheat: only use pre-harvest if greenest part of the crop is <30% moisture.
  • Oats: may not be accepted by grain buyers if treated pre-harvest.
  • Malt Barley: will not be accepted by grain buyers if treated pre-harvest.

Glyphosate has come under increased scrutiny compared to other pesticides due to media attention generated by individuals and groups who do not support the use of pesticides in any capacity.

Press a thumbnail into the kernel with moderate pressure. If the indent bounces back, the crop is not dry enough to receive glyphosate application. | photo: Charlee McLaughlin

Unlike many products applied in the fall, spraying glyphosate when kernels are too green can result in residues that exceed maximum residue limits (MRLs) established by domestic and export customers.

If growers spray pre-harvest glyphosate when seed moisture content is above 30 per cent, traces of the product can be absorbed by the plant as it dries, leaving unacceptable residues behind. Because glyphosate will accumulate in the seed itself, longer storage time after the crop has been cut does not reduce residue levels.

Growers can ensure crops are mature enough to receive glyphosate application by waiting until the greenest part of the field has reached the hard dough stage. At this stage, the plant will be below 30 per cent seed moisture content.

One challenge growers face when timing pre-harvest glyphosate applications is uneven maturity across the field. Growers may want to spray when the bulk of crop is ready to receive the application, but if the greenest part of the field isn’t mature enough, residues could contaminate the entire lot. To account for uneven maturity, it’s important to check the entire field before making the decision to spray.

For ideal pre-harvest glyphosate timing, there is a quick in-field test to make sure kernels have reached the hard dough stage. Press a thumbnail into the kernel with moderate pressure. If the indent bounces back, the crop is not dry enough to spray glyphosate. If the indent stays, the crop has reached 30 per cent moisture or lower and is fit to receive glyphosate application.

Click here to learn more about how fall application of glyphosate can affect market access for everyone.