A new app to assist canola growers to manage the risk of the fungal disease Sclerotinia stem rot is being developed, which incorporates new research to help determine when crops are susceptible to infection.
Sclerotinia is currently the most unpredictable disease that threatens Western Australian canola crops, which, with suitable conditions, can affect up to 20 per cent of crops across the Grainbelt.
Laboratory research by the Department of Primary Industries and Regional Development, supported by the Grains Research and Development Corporation (GRDC), has investigated the temperature range that triggers crop infection.
Sclerotinia stem rot is caused by the fungus Sclerotinia sclerotiorum, which survives between seasons in the soil as a fruiting body known as sclerotia.
Sclerotia germinate in cool conditions to produce apothecia, tiny mushroom-like bodies, which in turn release spores that are spread by the wind, infecting canola crops via flower petals.
Department research officer Ciara Beard and her team have identified the temperature range for different regions at which germination of sclerotia occurs, which will be crucial to the apps’ output.
“We found that germination of sclerotia is favoured in temperatures ranging from 10 to 20°C, while no germination was detected at high temperatures from 16-29°C,” she said.
“Under favourable conditions of 10 to 20°C and ongoing moisture, apothecia can be produced multiple times, surviving from two to five weeks over a three month period, potentially placing crops at risk for some time.”
Ms Beard said the laboratory results could be applied to different regions, to help identify when canola crops could be at risk of infection.
“In an average year, assuming sufficient moisture, cooler regions, like Esperance, could expect sclerotia germination from May to October, while warmer regions, such as Mingenew, are likely to be at risk from June to September,” she said.
“If this period overlaps with the flowering window, the risk of stem infection is elevated.”
The data from the research, as well as several years of field trials and observations, is being incorporated into an app that assesses whether canola paddocks in a given season are at risk of sclerotinia stem rot infection.
The app will be tested later in 2018 and available for the 2019 growing season for Android and iOS devices.
“The sclerotinia app will assist canola growers in making decisions on management and fungicide strategies to reduce economic losses from the disease,” Ms Beard said.
There has been increasing interest from canola growers in treating sclerotia like weed seeds and employing similar strategies, such as windrow burning and grinding chaff.
To that end, the research team investigated the use of a Harrington Seed Destructor on sclerotinia viability.
“Sclerotia were ground-up in laboratory experiments to simulate the Harrington Seed Destructor to four different levels of coarseness,” Ms Beard said.
“All four grinds germinated, with only the finest grind showing lower and delayed germination.”
“Unless the Harrington Seed Destructor can consistently grind sclerotia to less than 0.5 millimetres, it would not be considered an effective strategy.”
“Further research is required to determine whether the volume of spores released is reduced by grinding, as the apothecia from ground sclerotia were notably smaller.”
More details about the sclerotinia research and the app will be discussed at the 2018 GRDC Grains Research Update on Monday, 26 and Tuesday 27 February 2018 at Crown Perth and at the Northampton update on Friday, 23 February 2018.
Source: Department of Primary Industries and Regional Development
Image: A sclerotinia stem rot management app is being developed to help predict whether canola paddocks are at risk of the disease, based on when the fungus germinates to produce apothecia (pictured), which generate spores to spread the disease. Image supplied by Department of Primary Industries and Regional Development.