Australia
September 27, 2016

Researchers are advising growers in the southern part of NSW to be aware of significant disease risks and emerging fungicide resistance in the state this growing season.

NSW DPI researcher Andrew Milgate said as growers move in winter cropping in 2016, they should be particularly mindful of Septoria tritici blotch or STB.

He said the 2015 season presented many challenges for growers, with early sowing and wet weather creating ideal conditions for early infection, but there is the potential 2016 to also be problematic.

“Although this wheat foliar disease has not been common in southern NSW for more than a decade, it has become a significant disease in the high rainfall regions of Victoria, South Australia and Tasmania,” he said.

“It’s re-emergence in these regions poses a threat to those early sown high rainfall areas in NSW.

STB infections are often indicated by distinctive black fruiting bodies of lead lesions, and the disease requires long periods of lead moisture for it to develop.

“There is particular concern because of changes detected in virulence to variety resistance and the discovery of fungicide resistance developing in the Australian population of this pathogen,” Dr Milgate said.

“It has a long spore dispersal mechanism, which means that spores released from stubble during Autumn in Victoria could be blown onto and infect emerging wheat crops in NSW.”

The triazole fungicide resistance status in Australia has been further confirmed in additional isolates collected from Victoria, South Australia and Tasmania in the last 12 months. The presence of isolates containing resistance mutations in NSW has been confirmed.

“The levels of resistance detected thus far by our screening show that most fungicides will still be effected in the paddock,” Dr Milgate said.

“However to avoid further losses in efficacy growers are encouraged to used multiple strategies against the disease.

“In addition to mixing or rotating fungicides, an integrated approach to disease control should include crop rotation and the avoidance of susceptible cultivars to reduce inoculum loads will reduce the likelihood of fungicide resistance developing.”

It is critical that growers adopt strategies to reduce selection rates of further mutations so the useful life of currently available fungicides is extended.

“One strategy which is expected to slow the selection of more resistant strains is to mix or alternate different azoles,” Dr Milgate said.

“Equally in crops where two fungicide applications are to occur the same active shouldn’t be used in both applications.

“Growers must always follow label guidelines and ensure maximum residue limits are adhered to at all times.”

While the risk of widespread infection and subsequent crop losses in the low to medium rainfall areas of NSW, southern NSW’s higher rainfall areas have the weather conditions conducive to STB.

“Integrated disease management aimed at reducing the overall disease burden on crops will improve yields and help prevent growing fungicide resistance, which is real and present in NSW.”

For more information of STB visit www.grdc.com.au/GRDC-FS-Septoria-Tritici-Blotch-Wheat

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

Published: September 27, 2016