The two key weed species in canola crops in southern Australia are annual ryegrass (Lolium rigidum) and wild radish (Raphanus raphanistrum). Both weeds can be particularly challenging in a winter cropping program as they may germinate throughout the winter cropping phase, produce high seed populations and are resistant to multiple herbicide modes of action.
Growers have included Roundup Ready canola in their rotations as it provides strong control of both annual ryegrass and wild radish, especially in paddocks where there is confirmed or suspected clethodim resistant ryegrass populations.
Monsanto recently 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 were selected for their varying annual ryegrass and/or wild radish pressure and suspected herbicide resistance.
The treatments tested were typical use patterns for the three different herbicide tolerant canola systems:
|Roundup Ready canola||Roundup Ready Herbicide with PLANTSHIELD® by Monsanto 0.9 kg/ha @ cotyledon to 2 leaf, followed by 0.9 kg/ha @ 4 to 6 leaf.|
|Clearfield canola||750 mL/ha Intervix® + 0.5% Hasten™ + 500 mL/ha Select® @ 2 to 6 leaf.|
|Triazine Tolerant canola||1.1 kg/ha Atrazine PSPE followed by 1.1 kg/ha Atrazine +0.5% Hasten™
+ 500 mL/ha Select® + 1.0% Liase @ 2 to 6 leaf.
The study showed Roundup Ready canola offers excellent weed control of the key winter weed species: annual ryegrass and wild radish in paddocks with low to high weed pressure and in the situation of clethodim resistant ryegrass.
Roundup Ready canola provides significantly higher weed control in situations where there are high populations of ryegrass resistant to group a and b herbicides.
The Calingiri site had a high density of ryegrass with suspected clethodim resistance. Multiple germinations of this population occured during the growing season. This population density, resistance status simulates the situation many growers throughout southern Australia would be encountering.
Roundup Ready canola delivered significantly greater ryegrass control, in comparison with Triazine Tolerant and Clearfield canola by the end of the growing season.
Roundup Ready canola is as effective on wild radish as residual herbicide systems.
Low to moderate pressure of wild radish was present at the Corrigin trial site with one main germination event occurring during the growing season. Canola paddocks throughout southern Australia and especially Western Australia will often have wild radish present as the dominant weed species as was the case at this trial site.
Two applications of Roundup Ready Herbicide with PLANTSHIELD by Monsanto achieved high levels of control equivalent to the residual herbicide systems.
New South Wales
Applying two applications of Roundup Ready Herbicide with PLANTSHIELD by Monsanto, the first at 0-2 leaf and the second at 4-6 leaf provides the highest level of weed control.
The Monteagle site demonstrated that two sprays of Roundup Ready Herbicide with PLANTSHIELD by Monsanto prior to the 6 leaf stage achieved higher annual ryegrass control, relative to a single application at the 2 leaf or 6 leaf stage in a moderate population of ryegrass. The early spray application in a tow spray strategy is also critical to minimise early weed competition, therefore maximising yield potential.
Group b resistance is widespread across Victoria. Roundup Ready canola achieves higher levels of control than Clearfield.
The Goroke site in Victoria featured a mix of a low population of annual ryegrass and low and patchy populations of sowthistle and vetch (only the ryegrass data is presented). Under these conditions, Roundup Ready canola achieved greater final annual ryegrass control compared to Triazine Tolerant canola and significantly greater control than Clearfield canola