Volunteer canola

Brassica napus

The majority of volunteer canola seedlings emerge during the year following a canola crop. With several different herbicide tolerant canola varieties available, consideration should be given to the herbicide tolerance of the volunteers so the correct tools can be utilised for their control. For example, applying glyphosate to Roundup Ready^® canola volunteers will not control them.

Description:

At the seedling stage, canola can be confused with wild radish, however canola has cotyledons shaped more kidney-like (with a flat bottom) while wild radish cotyledons are more heart-shaped. The leaves of wild radish plants are much hairier than canola leaves which are more commonly hairless. Both plants develop as a rosette initially before the main stem elongates. Canola flowers are yellow, while wild radish are mainly yellow or white but can also be a pink or purple colour.

Control:

With a range of herbicide tolerant canola available, it is crucial to consider the previous cropping history to choose a suitable herbicide. While most volunteer canola will germinate the following year, canola seed can be viable for up to three years and longer if buried. For more consistent and effective results, control should be targeted at small canola that is less than 4 leaf.

Velocity® is registered for the control of 2-8 leaf volunteer canola in wheat, barley, cereal rye and triticale while Precept® and Eclipse® have the same crop registrations as Velocity, with the addition of oats. Tramat® is also registered for the control of cruciferous weeds (members of the Brassicaceae family).

References:

Australian Oilseeds Federation (2014), ‘Canola volunteer control’ http://www.australianoilseeds.com/__data/assets/pdf_file/0018/9261/Canola_volunteer_control_guide_-_2014.pdf

GRDC (2014), ‘Wild Radish Fact Sheet: Western, Southern and Northern Regions’, https://grdc.com.au/__data/assets/pdf_file/0023/117248/grdc_fs_wildradish_high-res-pdf.pdf.pdf

Herbiguide (2014), ‘Canola’, http://www.herbiguide.com.au/Descriptions/hg_Canola.htm

Related Pests

Annual phalaris

Phalaris paradoxa

Annual phalaris is an aggressive annual grass weed that is generally a more serious problem in northern New South Wales and southern Queensland than in other cropping areas. It prefers alluvial, sandy-clay or clay texture soils with high soil moisture.

Indian hedge mustard

Sisymbrium orientale

Indian hedge mustard is found in the cropping areas of Western Australia, northern and western New South Wales and southern Queensland. Its seeds are included in the ‘small foreign seeds’ fraction of allowable grain contaminants.

Annual ryegrass

Lolium rigidum

Annual ryegrass (Wimmera ryegrass) is arguably the most important grass weed competing with winter cereal crops in Australia. The rapid spread of herbicide-resistant populations in recent years has even threatened the viability of cropping in some areas.