Canola pod alert in SA

Disease expert Steve Marcroft said that in the 2013 season, blackleg pod infection was observed in all monitored regions of the state.

"But there was relatively low blackleg severity in 2013, which I put down to the dry start to the season," he said.

"There was identification at most sites across SA, predominantly with low levels of infection, but there were some sites with high levels of infection."

Pod infection was assessed on six cultivars at each site monitored – at Arthurton on the YP, Bordertown in the SE, Mount Hope on the EP, Riverton and Spalding in the Mid North and Turretfield in the Lower North – and chosen as they represented the resistance group used in blackleg management (groups A, B, C, D, E and G).

Plants were assessed by counting all pods on randomly selected plants and then counting the number of lesions to determine the percentage of infected pods on each plant.

Cultivar and regional effects were recorded with groups D, E and G showing none – or very low – pod infection.

Although pod infection was not shown to be correlated to stem canker infection, it was clearly evident that in cultivars which have effective seeding resistance (such as Group D, E and G), very little – if any – pod infection was observed compared to those reliant on adult plants' resistance (groups A, B and C).

This data suggests that seedling resistance may play a role in controlling pod infection.

Dr Marcroft said there were some concerning results from last season.

"We saw blackleg disease in Group Es for the first time last season," he said,

In the 2013 season, the Group E-resistant cultivar Thumper TT was observed to have higher-than-average levels of blackleg infection at a site in the EP.

"If you are on the lower EP and have grown Group E cultivars over the past two years, disease severity may increase," Dr Marcroft said.

* Full report in Stock Journal, July 24, 2014 issue.