Sclerotinia tops canola watch list
Grains Research and Development Corporation (GRDC) funded research on the management of pulse and oilseed diseases through the NSW Department of Primary Industries (DPI) shows some clear patterns from the last few years.
DPI plant pathologist Dr Kurt Lindbeck says in particular the 2015 season offered valuable lessons on sclerotinia incidence and management which can be used to stay ahead of the game this winter.
“There is a pattern in the development of sclerotinia with most outbreaks occurring in those districts with a frequent history of the disease, and those areas which have had a high intensity of canola and reliable spring rainfall,” Dr Lindbeck said.
“Outbreaks of sclerotinia stem rot tend to be sporadic, with levels of disease varying between seasons and regions in southern NSW and northern Victoria, so our advice is for growers to get out into their crops to monitor the situation.
“The disease can cause yield reductions of 30 to 40 per cent in heavily infested crops in high-rainfall years, and last year the first warning signs appeared in early August, with apothecia observed in canola crops in southern NSW, and continued wet weather through the month providing periods of extended leaf wetness and opportunities for disease epidemics to develop.”
Dr Lindbeck is based at the Wagga Wagga Agricultural Institute, where he leads GRDC-funded research on the management of pulse and oilseed diseases. He said prolonged wet weather through winter and early spring are ideal for the development of apothecia, the fruiting structures of the sclerotinia fungus.
“The complexity of the sclerotinia stem rot cycle means outbreaks are more sporadic than other diseases, because weather conditions must be favourable for the pathogen at each stage of development,” he said.
“There are no commercial canola varieties with resistance to sclerotinia stem rot available to Australian growers, so disease management relies on the use of cultural and chemical controls.
“Foliar fungicides should be considered in high-risk regions where the disease frequently occurs, there is a long flowering period and reliable spring rainfall.”
The decision to use a foliar fungicide will be governed by pathogen presence, the occurrence of conditions favourable for disease development (including rainfall and rainfall duration), crop growth stage, crop yield potential and canola prices.
There are several foliar fungicides to manage sclerotinia stem rot registered for use in Australia.
“Growers can monitor crops for disease development and identify the type of stem infection to get an indication of the timing of infection,” Dr Lindbeck explained.
“Main stem infections cause the greatest yield loss and indicate infection events early in the growing season, while branch infections can develop later in the season and generally result in a lower yield loss.
“Plants are susceptible to infection once flowering starts, with research showing a single fungicide application at 20 to 30 per cent bloom or 14 -16 flowers on the main stem is often effective in reducing yield losses from sclerotinia stem rot by preventing main stem infections.
“Growers should also remember that a foliar fungicide is a protectant, and has no curative capabilities, so it is only effective when applied before an infection event, during flowering.”
For more information, download the Sclerotinia Stem Rot in Canola Factsheet from the GRDC website.
Bernadette York, NSW DPI media officer
0427 773 785
Ellen McNamara, Cox Inall Communications
0429 897 129
GRDC Project Code DAN00177, UM00051