May 30, 2007
GRDC's The Crop Doctor
Blackleg management strategies can be improved by enhancing
canola growers’ understanding of the disease and how it
interacts with the environment.
According to GRDC supported Department of Agriculture and Food
WA Plant Pathologist, Ravjit Khangura, forecasting the onset and
dynamics of blackleg spore showers would help better quantify
the risk of blackleg and appropriately align management
strategies with the risk of yield loss.
Blackleg resistance annually costs WA graingrowers more than $20
The GRDC supported research investigated the susceptibility
window of canola to blackleg, discovering that canola is more
vulnerable up to the six leaf stage.
Crown canker severity, arising from exposure to stubble-borne
ascospores, was significantly less in six leaf or older plants
than four leaf plants.
Manipulating sowing date can avoid peak ascospore shower
activity in young canola and reduce risk of severe blackleg.
Dr Khangura said the susceptibility period might vary, according
to sowing times, in different regions and seasons.
A crop sown end of May to mid-June may be susceptible for up to
10 weeks or more, compared with crops sown during the early to
mid-May period that have a shorter susceptibility window.
In high disease pressure situations, particularly for late sown
crops, protection from blackleg may be required for longer
periods for moderately susceptible to moderately resistant
The three key elements in blackleg management are sowing
resistant varieties, reducing spore shower risk and applying
However, developing the blackleg sporacle model has
significantly defined regional and seasonal blackleg risk.
Predicting blackleg spore shower onset and fallout at the
critical stage of canola susceptibility helps growers better
understand the risk of blackleg and allows them to apply
appropriate cost-effective control strategies.
The Crop Doctor is
GRDC Managing Director,