Perennial weed control is best achieved with pre-harvest applications of glyphosate. Once again planning your rotation will give you the opportunity to control these tough perennials in the crop you want so harvest and weed staging work together. Many farmers do not like to use pre-harvest in canola because they feel to damage from the sprayer is more than acceptable. Pulses should be a good candidate for pre-harvest, as it will also help dry down the crop for harvest. The problem in pulse crops is when you have high thistle populations, the pulses are not competitive, and where the thistles are, you have no crop at all.
Many farmers like to control the perennial weeds before they plant their pulse crops.
That leaves cereal crops for the pre-harvest application. But if you are trying for malt barley, the maltsters don't want glyphosate residues on the barley. The crop of choice by many farmers is the other cereal crops and Flax. One additional benefit of spraying Roundup on flax is that it also stops the flax from continuing to grow and the moisture is saved for the next year's crop. If pre-harvest Roundup is applied to the cereal crop in year 4 for perennial weed control, you can then assess the control in the oilseed crop in year 1 of the chart.