Growers urged not to grow canola on canola to prevent disease risk and crop losses

Author: | Date: 24 Feb 2012

Blackleg in canola. Photo courtesy Ray Colwey

Growers urged not to grow canola on canola to prevent disease risk and crop losses

Canola growers throughout the southern cropping region are being urged to implement pre-sowing management strategies to prevent significant disease-inflicted crop losses this coming season and to avoid risking the canola industry’s long-term future.

The risk of blackleg infection in crops and potential for yield losses this year is severe due to the increased area sown to canola in 2011 and the prediction of another large planting in 2012 due to favourable oilseed prices.

Blackleg is the most severe disease of canola in Australia. Because it survives on canola stubble, last year’s expansive crop has heightened the risk this season.

Blackleg experts, with support from the Grains Research and Development Corporation (GRDC), are urging growers to put in place management strategies now, before the 2012 crop is sown.

The National Brassica Pathology Working Group, comprising pathologists, agronomists, chemical companies and canola breeders from across Australia, unilaterally shared concern at a recent meeting in Melbourne that growers would potentially face serious risk of crop failure due to blackleg if attempting to grow canola on canola.

The working group says if growers increase canola intensity to the point where canola is sown onto last year’s canola paddocks, disease severity will be extreme, resulting in major crop losses and in some instances complete crop failure.

Shannon Potter MarcroftWorking group spokesperson and blackleg authority, Steve Marcroft, of Marcroft Grains Pathology, says that an even worse scenario is that the fungal pathogen will overcome cultivar resistance genes, resulting in many cultivars being destroyed.

“Growers are urged not to risk the long-term viability of the canola industry by sowing canola on canola,” said Dr Marcroft, on behalf of the National Brassica Pathology Working Group.

Growers should consult the most recent Blackleg Ratings to choose a resistant cultivar, separate this year’s canola crop from last year’s stubble, and use either a fungicide seed dressing or fungicide-amended fertiliser as effective strategies for managing blackleg.

“Blackleg is managed by breeding disease resistance into canola cultivars and by crop management practices,” Dr Marcroft said. “However, the blackleg fungus is adept at overcoming cultivar resistance, leaving many crops vulnerable to significant yield loss.”

Dr Marcroft says growers and farm advisers in South Australia, Victoria and southern New South Wales need to be aware that blackleg was becoming more prevalent in areas where it had previously not been detected, and that being aware of neighbours’ cropping programs was also vital.

Growers and advisers should therefore refer to a number of sources of information to frame their management strategies this year.

The GRDC and Dr Marcroft recommend that growers consult the Blackleg Risk Assessor fact sheet for advice on all blackleg control practices.

The Blackleg Risk Assessor was developed by the GRDC and industry partners to help farmers make the right choices before sowing canola.

Dr Marcroft, who has been addressing GRDC grains research Updates in the southern region about the blackleg scenario, says growers can use the Risk Assessor to determine if their paddocks are in a high risk situation, and what practices could be changed to reduce yield loss from blackleg.

“It lists all the factors that will influence blackleg severity on a grower’s property,” he said.

The regional performance of commercial canola cultivars and blackleg resistance ratings are available via the National Variety Trials online resource at www.nvtonline.com.au.

In the future, information on the rotation of canola cultivars and resistance grouping of cultivars will also be made available.

“The recommended canola rotation groups will be released to industry in spring 2012 after extensive feedback from industry to ensure a proposed new blackleg management system is both effective and easily adopted by growers,” said Dr Marcroft, who is the national blackleg ratings coordinator.

“In the meantime, growers and advisers should be aware that control of disease is an integral component of canola production and has to be considered at all points of crop management,” he said.


Caption: Canola stalks (on the right) infected with blackleg. Photo: Ray Cowley (NSW DPI).

Caption: GRDC Southern Regional Panel chair David Shannon (left) with South Australian Research and Development Institute research scientist Trent Potter and Steve Marcroft, of Marcroft Grains Pathology, at the GRDC grains research Update in Adelaide this week where the threat of blackleg was discussed.


GRDC Project Codes: DAN0115, UM0034, UM0042, MGP0002

For further information: Dr Steve Marcroft
Marcroft Grains Pathology
0409 978 941

Contact: Sharon Watt
Porter Novelli
0409 675100

GRDC Project Code DAN0115, UM0034, UM0042, MGP0002