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