August 13, 2013
The Department of Primary Industries (DPI) is urging canola growers in southern NSW to be on the look out for Sclerotinia stem rot following cool, wet conditions which have been ideal for spore production.
DPI Plant Pathologist, Kurt Lindbeck, said the warning follows the detection of the fungus in the field and subsequent petal tests that found levels of infection as high as 100 per cent from some early flowering crops.
“Sclerotinia stem rot can result in yield losses of up to 30 per cent,” Mr Lindbeck said.
“Conditions which allow the lower crop canopy to remain wet for extended periods, such as fogs, heavy dews or rainfall events, are ideal for stem infection to occur.
“The main concern is for canola crops which are flowering now, some three to four weeks earlier than normal in districts where the disease is known to frequently occur.
“The fungal spores infect and colonise canola petals, which allows the fungus to build up in energy, and will lead to stem infection when those petals fall into the crop canopy and lodge onto a wet stem.”
Mr Lindbeck said the main districts at risk include south of Henty, east of Cootamundra and further north towards Cowra and where there is a history of this disease in recent years.
“At this point in time, growers should be considering the potential risk of the disease as foliar fungicides have to be applied early in the flowering period,” Mr Lindbeck said.
“The ideal timing of foliar fungicide application to manage sclerotinia stem rot is at 20 – 30 per cent flowering.
“In the paddock this is when the majority of canola plants have 15 – 20 flowers open on the main stem.
“At this growth stage a foliar fungicide application will protect early flowers from infection, but also allow penetration of the fungicide product into the crop canopy to protect lower stems and leaves from infection.
“The use of high water rates is preferable for good coverage and penetration into the crop canopy.”
Growers should check with their local rural supplier for the current registered fungicides for management of sclerotinia in canola.