The extended dry spell, which stretched for many between harvest and early June, has seen volunteer canola emerge as an issue this season.
With very little summer and early spring rain, volunteers had no opportunity to germinate and to be subsequently controlled prior to sowing. As a consequence, and coupled with the fact that many crops were sown dry, volunteer canola has shot and emerged with the crop.
For many growers this year, deciding when and what to spray on paddocks where there is volunteer canola problem has been a challenge. Anecdotal evidence suggests that the problem is worse in paddocks where last year’s canola was windrowed, particularly where there were lighter windrows that may have blown around.
Direct-headed paddocks seem to have less of an issue with volunteers and any paddocks sprayed with Sakura® also appear to be cleaner (due to the suppression effect of Sakura).
In paddocks where Clearfield (CLF) wheat or barley has been sown following a Round-up Ready or TT canola variety, growers have had the option of using OnDuty® or Logran® pre-sowing. However with many growers opting for CLF canola varieties last year, followed with CLF wheat or barley, the same problem exists.
Herbicide options
Before spraying volunteer canola, growers should consider the crop growth stage as well as the density and vigour of the volunteers. Growers will need to decide if the canola is likely to smother the crop out or if the crop growth is slow enough to warrant delaying spraying.
Crop growth stage will certainly impact on the cost of the spray (with cheaper options available when the crop is bigger). However by delaying spraying there is also the risk that the volunteers will negatively affect crop growth and development, with the volunteer canola robbing nutrients and moisture from the soil.
Phenoxy sprays are still the cheapest and most effective option but cannot be used safely until the crop is at the four-leaf stage. As such growers will need to decide if the economic benefits from delaying spraying are likely to outweigh the damage uncontrolled volunteers will inflict on the crop. If left uncontrolled, dense strikes of canola (particularly in windrows) will smother emerging cereal plants and if left too long, those strips may not sufficiently recover, justifying earlier action.
Jaguar® is the only registered product that can be used when the crop is at the two-leaf stage. Lower rates of Velocity® have been considered but were found to be less effective and more expensive than Jaguar.
Jaguar and Velocity are safer to use on cereals early but will cost about $13 to $15/ha compared to LVE at $3 to $5/ha.
Some growers used Valor® (Group G) prior to sowing to suppress canola emergence however results have been varied and control has still been required. Shading and coverage can affect the herbicides ability to work, high water rates (>80L/ha) will improve control particularly when the population is dense.
BCG trials team staff have been trialling a range of herbicide options for volunteer canola control in cereals.
