Western Australia
April 13, 2012
Western Australia’s coming cropping season is expected to be a high risk year for blackleg disease in canola but growers can take steps to minimise the damage.
Department of Agriculture and Food (DAFWA) plant pathologist Ravjit Khangura said growers should select resistant varieties, not seed into or close to last year’s canola stubble and, if warranted, use a fungicide seed dressing or fungicide-amended fertiliser.
Blackleg lesions on a canola leaf
Dr Khangura, who oversees blackleg research in WA supported by the Grains Research and Development Corporation (GRDC), said there was a high risk of blackleg infection and subsequent yield losses in 2012.
This was due to high levels of blackleg inoculum producing spores from the big area of canola stubble left from last year’s crop.
It is expected there will be a large amount of WA farmland planted to canola in 2012 due to favourable prices.
Dr Khangura said growers should choose resistant cultivars by consulting recently released 2012 Blackleg Resistance Ratings at www.grdc.com.au/National-Blackleg-Ratings-2012
“These ratings are based on trials in disease nurseries – with very high blackleg pressure – in WA, Victoria, New South Wales and South Australia,” she said.
“Growers should select varieties with high levels of resistance which are suited to their area.
“They should be mindful that, under severe blackleg pressure, even varieties rated as resistant (R) may still suffer yield losses.”
Dr Khangura said growers should not grow canola on last year’s canola stubble and/or within 500 metres of last year’s canola stubble.
The National Brassica Pathology Working Group, of which she is a member, is concerned that growers will face the risk of crop failure due to blackleg if attempting to grow canola on canola.
“An even worse scenario is that the fungal pathogen will overcome cultivar resistance genes, resulting in currently resistant varieties becoming susceptible,” Dr Khangura said.
“Growers are urged not to risk the long-term viability of the canola industry by sowing canola on canola.”
Dr Khangura said that in addition to the 2012 Blackleg Resistance Ratings, growers should consult the Managing Blackleg bulletin which could be found by searching ‘bulletin 4571’ on the DAFWA website www.agric.wa.gov.au
Growers could ascertain the risk of blackleg infection in their region at www.agric.wa.gov.au/cropdisease.
The GRDC Blackleg Risk Assessor Fact Sheet, developed by Marcroft Grains Pathology with support from the GRDC, could also provide useful information on the risk of sowing varieties of varying levels of resistance in various paddock situations.
The fact sheet is available at www.grdc.com.au/GRDC-FS-BlacklegRiskAssessor
Information about the regional performance of commercial canola cultivars and blackleg resistance ratings are available via the National Variety Trials (NVT) online resource at www.nvtonline.com.au
Species
