Australia
May 19, 2017

Ratings in the Grains Research and Development Corporation (GRDC) Blackleg Management Guide, are reviewed every year by canola breeders and pathologists to give growers the latest information on cultivar resistance to blackleg.

With increased demand for canola seed leading to a shortage of some commercial seed supplies it is imperative that growers sowing seed retained from last year’s crops are aware of resistance ratings of cultivars, and that ratings may have changed. 

NSW DPI plant pathologist Dr Lindbeck warns the risk of blackleg in 2017 will be heightened due to the increased forecast canola plantings, but the actual disease severity will be strongly dependent on seasonal conditions
 
NSW Department of Primary Industries (DPI) plant pathologist, Kurt Lindbeck, says results from the latest blackleg screening of canola cultivars, undertaken as part of the GRDC-funded Blackleg Ratings agreement within the National Variety Trials, have been factored into the updated disease ratings for 2017.

“The resistance screenings have confirmed that the resistance status of some Group A cultivars has changed and growers must be aware of these new ratings before they sow this year’s canola crops,” Dr Lindbeck says.

“If open pollinated (OP) cultivars were grown in 2016 and growers plan to sow seed retained from these crops this year, it is vital they check the 2017 blackleg ratings.

“For example, ATR Bonito and ATR Wahoo previously each had a moderately resistant (MR) rating, but that has fallen to moderately susceptible (MS).

“An MS cultivar may not be suitable for medium to higher rainfall zones if not adequately protected.

“When sowing retained MS cultivars in higher rainfall zones, growers should protect seed with Jockey® and use fertiliser treated with Impact In-Furrow® and budget for a foliar fungicide to apply if required.”

The grains industry is anticipating a significant increase in plantings of canola in 2017 as prices for the oilseed continue to be more favourable than those for cereal grain.

This likely expansion in plantings will add another complexity to proactive management of blackleg this year, as a key strategy for minimising disease risk is sowing into paddocks at least 500 metres away from the previous year’s canola stubble.

“Crop rotations will be tight this year, so adequate separation of new crops from last year’s stubble will be problematic,” Dr Lindbeck said.

Blackleg is a sexually reproducing disease, which enables the pathogen to evolve. Fungal spores are released from canola stubble and spread extensively via wind and rain splash. The disease is more severe in areas with intensive canola production.

Blackleg has caused up to 90 per cent yield loss in trials and is cited as the number one threat to the canola industry.

Blackleg has historically been identified by the formation of crown cankers within crops, however upper canopy infections, where the disease infects branches, flowers and pods, are also proving to be an issue for some growers.

Dr Lindbeck says the wet winter and spring experienced in many parts of southern NSW in 2016 made for ideal blackleg conditions, with prolonged leaf wetness coinciding with peaks of ascospore release.

“The increased area of canola production, and increased sowing of Group A cultivars over the past five years are also possible reasons for the rise of the disease."

Dr Lindbeck warns that the risk of blackleg in 2017 will be heightened due to the increased forecast canola plantings, but the actual disease severity will be strongly dependent on seasonal conditions.

Growers are therefore advised to follow the recommended strategies for reducing the risk of blackleg disease which are contained in the GRDC Blackleg Management Guide.

“It is strongly recommended that growers use as many different strategies as possible to combat blackleg, including cultivar resistance, paddock selection and strategic use of fungicides," Dr Lindbeck said.

To further assist growers in determining the level of risk in their area, the GRDC-supported National Variety Trials (NVT) Online website, provides the latest information from blackleg monitoring sites across Australia.

Website: http://www.grdc.com.au

Published: May 19, 2017