But canola growers in the region can rest a little easier after the latest results from an ongoing survey by the Lower Eyre Agricultural Development Association determined the incidence and severity of the disease, giving them some idea of potential risks.

Caused by the fungus Leptosphaeria maculans, blackleg is the most serious disease affecting canola in Australia. While wet and mild conditions provide ideal growing conditions for the crop, they also suit blackleg.

In 2003, the region experienced a blackleg 'disaster' that resulted in devastating yield losses. Blackleg spores survive in stubble from previous years and proximity to previous crops and short rotations have been identified as contributing factors for higher levels of infection.

Extensive canola plantings on the lower Eyre Peninsula mean that the likelihood of exposure is high.

LEADA chairman David Giddings said it was essential to grow a range of varieties to prevent the fungus from building-up enough spores to wipe it out.

"The survey is powerful information which keeps an eye on where varieties are with their resistance and gives growers some idea of the potential risks to growing a specific variety," Mr Giddings said.

Undertaken since 2008, the surveys look at both commonly grown canola varieties and those newly released.

Stem samples are randomly selected along diagonal transects between windrows and scored for percentage blackleg internal infection in the stem cross-section at the base or crown.

"Newly released varieties with good blackleg-resistance characteristics are adopted rapidly by farmers so we look at those and also monitor commonly grown, well-established varieties," Mr Giddings said.

Last year, a survey of 35 paddocks looked at varieties of Garnet and 575CL. These varieties were chosen to provide a resistance comparison between the highest-rated of the Clearfield varieties and the widely grown Garnet.