GRDC Research Updates 2017: Annual ryegrass viable seed reduced by desiccation and swathing of canola

Page last updated: Tuesday, 11 February 2020 - 4:08pm

The viability of annual ryegrass seed can be reduced substantially by desiccation, pre-harvest spraying or swathing of canola depending on the product and timing.

Pre-harvest spray with greater than 2.0L/ha glyphosate weedmaster DST significantly reduced ryegrass seed viability by an average of 96% in 2013 at Katanning.

On average, desiccation with diquat reduced the viable ryegrass seed production by 65% in 2010 and 88% in 2013 but not in 2011 or 2012, which may be due to the spray timing being too late for the ryegrass.

Refer to summary below and presentation and paper under External Links.

Aims

To test the effect of desiccation, pre-harvest spraying, swathing and swather spraying on ryegrass seed viability at harvest of canola.

Results

The results from 2010-2013 showed that a pre-harvest spray with glyphosate or spraying glyphosate on a swather can reduce the viable ryegrass substantially although in 2012 there appeared to be no effect. Desiccation with diquat had no effect on viable ryegrass seed in 2011 and 2012 but did reduce viable ryegrass seed numbers in 2010 and 2013.

Conclusion

The results showed that desiccation with diquat, a pre-harvest spray with glyphosate or spraying glyphosate on a swather can reduce the viable ryegrass substantially. The ability of glyphosate to reduce seed viability when applied pre-harvest however, may depend on the timing.

The reduction in ryegrass viability can sometimes be greater when the glyphosate is sprayed pre-harvest and not swathed (compared to swathing) but this varied with season.

All desiccation and pre-harvest treatments had no effect on canola yield or oil content in 2012 and 2013 at Katanning although there were some small but variable reductions in yield in 2010 and oil in 2011 at Mount Barker.

Desiccation with diquat had no effect in 2011 and 2012 but in 2010 it reduced ryegrass seed viability to a similar extent as a pre-harvest spray with glyphosate or spraying glyphosate on a swather.

Contact information

Author

Glen Riethmuller