Canola growers are urged to assess their paddocks for sclerotinia stem rot and consider applying appropriate foliar fungicides to manage the damaging fungal disease.
Department of Agriculture and Food (DAFWA) plant pathologist Ravjit Khangura said sclerotinia had recently appeared in canola crops in locations including Esperance and Frankland River.
“Yield reductions from this disease, when uncontrolled, can be as high as 30 to 40 per cent – or up to 0.5 to 1 tonnes per hectare – in heavily infested crops in high rainfall years,” she said.
Dr Khangura said research funded by the Grains Research and Development Corporation (GRDC) had shown that fungicides applied to canola crops at the 20 to 30 per cent flowering stage were usually most effective in reducing yield losses caused by sclerotinia.
“Given the recent wet and humid conditions which are conducive to the disease, growers are advised to spray their paddocks at this stage of flowering if there is a history of sclerotinia in their paddock or adjacent paddocks,” she said.
“A single fungicide spray can usually reduce canola yield losses from sclerotinia when applied at the right time.
“In some districts with a history of high levels of sclerotinia and high crop yield potential, two fungicide applications may be cost effective.”
Dr Khangura said WA research had revealed that controlling sclerotinia using registered fungicides consistently increased crop yields in areas with high disease pressure.
She said growers should base fungicide use on disease risk; rainfall and crop biomass levels; maturity of the crop; crop yield potential; and canola prices.
Information about high risk situations and conditions conducive to outbreaks is available in the GRDC Fact Sheet Sclerotinia stem rot in canola.
Dr Khangura said sclerotinia survived in the soil for many years.
“Spores released from the fungal fruiting bodies (apothecia) initially infect canola petals, which subsequently drop into the plant canopy and can lead to leaf and stem lesions which cause lodging and yield loss,” she said.
“Sclerotia can sometimes germinate directly and cause basal stem infections. This is less common and generally infects only a fraction of plants that are present in close proximity to the sclerotes.”
Additional information about sclerotinia is available in the GRDC Back Pocket Guide Diseases of canola and their management and by searching ‘sclerotinia’ on the DAFWA website.
Caption: Leaf and subsequent stem lesions caused by sclerotinia stem rot can cause lodging and yield loss.
Ravjit Khangura, DAFWA
08 9368 3374
Natalie Lee, Senior Consultant, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code