Crop disease warning

CAUTION URGED: Dr Steve Marcroft is warning of a high blackleg disease risk for 2017 canola crops. The Grains Research and Development Corporation has developed a fact sheet to help farmers determing their individual crop risk.
CAUTION URGED: Dr Steve Marcroft is warning of a high blackleg disease risk for 2017 canola crops. The Grains Research and Development Corporation has developed a fact sheet to help farmers determing their individual crop risk.

CANOLA growers are being encouraged to assess the extent of blackleg disease in crops to reduce the risk of disease next year and beyond.

To support growers in determining current disease levels, the Grains Research and Development Corporation (GRDC) has released the 2017 Spring Blackleg Management Guide Fact Sheet, developed by the National Canola Pathology Project team.

The guide outlines specific steps to manage blackleg and includes cultivar blackleg ratings and resistance groups for all canola cultivars, including new cultivars which will be available next year.

The resource can help growers assess if they are in a high-risk situation and guide them to minimise future yield losses.

Blackleg is a sexually reproducing pathogen that will overcome cultivar resistance genes and is more severe in areas of intensive canola production.

Oilseeds disease authority Steve Marcroft, of Marcroft Grains Pathology, said to assess disease levels in current crops, samples could be taken any time from the end of flowering to windrowing (swathing).

“Pull 60 randomly chosen stalks out of the ground, cut off the roots with a pair of secateurs and, using reference photographs in the GRDC fact sheet, estimate the amount of disease in the stem cross section,” he said.

“Yield loss commonly occurs when more than 50pc of the cross section of the cut stem is discoloured.”

Dr Marcroft said if growers identified they were at high risk, they should use management practices outlined in the fact sheet to reduce blackleg severity for coming seasons.

“They should also rotate between cultivars with different resistance genes to reduce the probability of resistance breakdown and reduce disease severity,” he said.

Dr Marcroft said if growers identified they were in a low risk situation and had not identified yield loss due to blackleg infection when assessing their crop, they should continue with their current management practices.

To further assist growers in determining the level of risk in their area, the GRDC’s National Variety Trials provides the latest information from blackleg monitoring sites across Australia.