Western Australia
March 1, 2016
Department of Agriculture and Food canola pathologist Dr Ravjit Khangura has undertaken research that shows that the timing of fungicide treatments to control sclerotinia stem rot in canola is crucial to protecting yields.
Canola trials in the South Stirlings have highlighted the importance in the timing of fungicide treatments to control sclerotinia stem rot to protect yields.
Research showing late applications of fungicide to treat the disease had no positive impact on yields results will be profiled today at the 2016 GRDC Grains Research Update, Perth.
While early spray applications targeted at crops with 25 to 50 per cent flowering were highly effective, late treatments after 60 to 80pc flowering were insignificant – even when the disease was controlled.
Department of Agriculture and Food canola pathologist Ravjit Khangura said with treatment costs about $50 per hectare, it was a difficult decision for growers to determine whether to spray or not.
“It is the greatest dilemma for people,” Dr Khangura said. “Growers can’t wait until the onset of symptoms, like leaf lesions and stem infection.
“For treatments to be truly effective, growers need to spray before the appearance of any symptoms, if there is to be any real yield advantage.
“That only gives growers about a three week window to determine whether or not to take action.”
Conditions were not conducive for sclerotinia stem rot last season, resulting in low levels of the disease in the northern region and moderate levels in the southern region – although some crops that had high disease pressure had infection levels of up to 40pc. The disease was not prevalent in the central region.
Dr Khangura said the trials also showed that while treatments were effective for crops facing a high risk situation, in some cases preventative applications might not have been required if the risk of the disease was low.
“To determine whether or not to treat, growers really need to understand their paddock history and marry that with the rainfall outlook,” she said.
“Previous data has shown that 40 millimetres or more rainfall in the lead up to flowering and a humidity level of more than 75pc with another 40mm forecast in coming weeks and continued humidity is required to induce spore set and subsequently disease development.
“The risk is also elevated by the disease level from the previous years and whether there is sufficient inoculum for sclerotinia stem rot to become a problem in canola.”
The department also evaluated the performance of two registered and four non-registered fungicides on sclerotinia stem rot on the South Stirlings crop.
“All products showed similar efficacy, except for one unregistered product,” Dr Khangura said.
“The registered chemicals performed well, while two of the non-registered treatments had an adequate response, providing valuable data for the commercial sector to review and to consider pursuing registration.”
Sclerotinia research involving field trials will continue this year across northern and southern canola growing regions of WA, as part of the Grains Research and Development Corporation’s National Canola Pathology Program.
To view the paper visit giwa.org.au Details about forthcoming Regional Grains Research Updates is online at giwa.org.au/2016researchupdates
For more information about sclerotinia stem rot visit agric.wa.gov.au
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