Fungicide applications are essential to successfully control the fungal disease sclerotinia stem rot in canola, above all other mitigation measures.
This finding from a series of trials by the Department of Agriculture and Food will be profiled at the Grains Research and Development Corporation’s (GRDC) Research Update in Perth on 27-28 February.
Sclerotinia was widespread across the Grainbelt in 2016, with favourable conditions triggering an unusually high level of ground (basal) infections in the central and southern regions.
Department research, funded by the GRDC, found that fungicides, especially those applied at the early stage of infection, were effective in controlling sclerotinia ground infection and improving canola yields.
“In a fungicide timing trial, all treatments applied at several bloom stages of the crop, from 10 per cent through to three weeks after 50 per cent of the crop was in bloom, were effective, with the best control and net return achieved by a double spray application,” research officer Ravjit Khangura said.
Fungicide treatments were tested at Moonyoonooka, New Norcia, Darkan and Arthur River.
“Fungicides were effective in reducing disease levels though the yield responses were variable,” Dr Khangura said.
“The net return for various treatment timings ranged from between $41, for crops sprayed at 10 per cent bloom, to $148 for crops sprayed twice at 10 per cent and 50 per cent bloom.”
The 2016 trials also compared the effectiveness of wide row spacing (44 cm) and low plant densities to manage sclerotinia.
Dr Khangura said while neither sowing practise mitigated the disease incidence, a higher plant density of more than 23 plants per square metre significantly improved yield in a perfect growing environment.
“The results have shown that wide row spacing or lower plant densities alone do not provide reliable disease control,” Dr Khangura said.
“It demonstrates that fungicide application at flowering remains the most effective way to minimise losses from Sclerotinia stem rot, highlighting the importance of budgeting for fungicide.”
With increasing incidences of sclerotinia ground infections, Dr Khangura examined the effectiveness of fungicide applications to control the disease in the Central and Southern regions of WA.
“Basal infections have been rising in recent years and 2016 was the worst season I have ever seen,” she said.
“Data from three different trials indicate that fungicide applications can significantly reduce the disease incidence by reducing the secondary spread of the disease.”
With the widespread presence of sclerotinia in 2016, canola growers have been reminded to take preventative measures to minimise the impact of the disease, which can causes yield losses of up to 40 per cent.
“As the disease has been widespread over the past few years, there will be plenty of inoculum present to infect this year’s crops,” Dr Khangura said.
“Growers should use clean seed that is free of sclerotes, employ long rotations and avoid planting into paddocks that have recently been sown to broadleaf crops.
“Sclerotinia has also been known to be spread by the wind for up to 100 metres, so it would be wise not to plant next to canola or lupin paddocks that were affected with Sclerotinia last year.”
Dr Khangura and colleague Mark Seymour will be part of a panel to discuss management strategies for sclerotinia in 2017 and beyond at the Canola Disease Focus Session of Grains Research Updates on 28 February.
The panel will include Canadian canola pathologist Dr Lone Buchwaldt, Geoff Fosbery, ConsultAg, Rick Horbury, Bayer, Matthew Denton-Giles and Mark Gibberd from the Centre for Crop and Disease Management at Curtin University.
For more information about sclerotinia stem rot control measures visit agric.wa.gov.au and search for ‘managing sclerotinia’.
Media contacts: Jodie Thomson/Megan Broad, media liaison +61 (0)8 9368 3937