Annual ryegrass (Lolium rigidum) and wild radish (Raphanus raphanistrum) can be particularly challenging in a winter cropping program with multiple germinations throughout the season, which produce high seed populations and are potentially resistant to multiple herbicide modes of action.

Where growers have included Roundup Ready canola in their rotations, strong control of both annual ryegrass and wild radish, especially in paddocks where there is confirmed or suspected clethodim resistant ryegrass populations, has been achieved.

Monsanto has compared the weed control of annual ryegrass and wild radish that can be achieved with Roundup Ready canola, Clearfield canola and Triazine Tolerant canola systems. Multiple trial sites across Western Australia, New South Wales and Victoria over the past 10 years have been selected for their varying annual ryegrass and/or wild radish pressure and suspected herbicide resistance.

In 2017, an annual ryegrass control trial was conducted in Calingiri, WA comparing Roundup Ready canola with one and two sprays of Roundup Ready Herbicide with PLANTSHIELD by Monsanto, along with ATR Bonito with a typical commercial regime of atrazine and clethodim. The trial site had a moderate ryegrass population that was suspected to be susceptible to clethodim. The results showed the high levels of ryegrass control achieved when two sprays are applied in a Roundup Ready canola system. The trial also emphasised the impact inadequate ryegrass control can have on canola yield. Results from the trial are presented below:

2017 Weed Control Trial results graph

Alternative post-emergent chemical group with no residual plant back

The Roundup Ready canola system provides superior weed control and enables you to use an alternative herbicide group in the early post-emergence phase (Application window: emergence to 6 leaf).

The use of Roundup Ready Herbicide with PLANTSHIELD by Monsanto has no residual carry-over into following crops. However, if dual tolerance Roundup Ready/Triazine varieties are grown, triazine residues will need to be considered and crop selection managed to mitigate potential following season crop effects.

Using crop biomass to compete with weeds

Roundup Ready canola hybrid varieties have excellent early season vigour providing greater crop competition for emerging weeds.

Roundup Ready hybrid varieties develop canopy closure faster than non-hybrid canola varieties. Hybrid early vigour is another key advantage of the Roundup Ready system as increased crop competition reduces the reliance on herbicides to control weeds.