AN UNWANTED by-product of the wet spring down the east coast will be outbreaks of sclerotinia disease in canola far further into medium and low rainfall zones.
Rohan Brill, NSW DPI canola agronomist, said central to sclerotinia’s development is a wet canopy for consecutive days.
“Normally this does not occur apart from in high rainfall zones, but this year will be the exception, with constant showers keeping the canopy wet,” Mr Brill said at last week’s Birchip Cropping Group (BCG) main field day.
He also said the wet conditions would be conducive to aerial blackleg, which impacts flowers, stems and pods instead of forming cankers like conventional blackleg.
In terms of time of sowing, Mr Brill said it was difficult to say just yet whether the push to early sowing dates was exposing canola plants to more disease pressure.
“It may be a help with some diseases and a hindrance for others, and also we will not see conditions so wet as this every year, so we shouldn’t make a definitive decision on what happens this year.”
He said one of the important lessons he had learnt in his research had been the importance of large seed in getting good germination rates.
Mr Brill recommended that growers using their own open pollinated seed to sow the following year’s crop should grade it and keep the top ten per cent for sowing before selling the rest.
“So if you have got 30 tonnes, grade it with a 2mm screen and keep around three tonnes of the largest seed.”
“The research shows larger seed has a much better germination rate and early vigour.”
In terms of row spacings, he said anything out to 37.5cm (15 inch) could work well in most environments.
“It is about getting the optimum number of plant numbers, so it is more to do with sowing rate than row spacings, but we find if you go too wide then you get too many plants in the one row which creates problems.
“There is also the issue that if you out on something like 75cm (30 inch) spacings you will never get full canopy closure and that means weeds will have the chance to compete so that also can be an issue.”