New season rust control tactics

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The Rust Bust

Growers are reminded to implement rust-control strategies to help shield 2014’s winter cereal crops from yield losses.

An effective strategy to destroy the ‘green bridge’ involves herbicide spraying or grazing, selecting rust-resistant varieties and developing tactics for fungicide applications.

In particular, growers are encouraged to target volunteer cereals with herbicides before mid-March.

Paddocks where rust-susceptible varieties were sown in 2013 are especially likely to aid the survival of the fungus over summer, leading to the carryover of inoculum at seeding in 2014.

Variety selection guided by rust-resistance ratings is another control measure that can help growers avoid yield losses and reduce expenditure on fungicides.

Changes in 2013 to the distribution and pathogenicity of rust diseases also needs to be considered when deciding on variety selection and fungicide spraying.

In 2013, the Australian Cereal Rust Survey, based at the University of Sydney’s Plant Breeding Institute (PBI), found some important changes in rust diseases across Australia.

PBI Cereal Rust Reports, which outline how new rust distributions and pathogenicities may impact on the susceptibility of varieties, are available via the University of Sydney website (http://sydney.edu.au/agriculture/plant_breeding_institute) .

Photo of wheat showing symptoms of stripe rust leaf

Wheat stripe rust leaf infection on a moderately susceptible wheat variety.

PHOTO: Brad Collis

Rust-infected plant samples collected from NaparooPBR logo wheat crops in northern New South Wales were identified as a new wheat leaf rust pathotype (76-3,5,7,9,10,12,13 +Lr37). This is the first time leaf rust pathotype has been detected with combined virulence for the rust-resistance genes Lr13, Lr37 and Lr24.

Following its discovery in northern NSW, the new pathotype has also been detected in southern Queensland.

Another development in eastern Australia that may influence the susceptibility of crop varieties this season was the spread of the ‘Pc91’ oat crown rust pathotype (1107-1,4,6,7,10,12 + Warrego + Nugene + Gwydir) in southern Queensland and northern NSW.

Adding to this is the spread of a ‘WA pathotype’ of wheat stripe rust with combined virulence for Yr17 and Yr27 (134 E16 A+17+27+). It has now moved from southern NSW into northern NSW, southern Queensland and Victoria.

In Western Australia, a new barley leaf rust pathotype (5457 P-) was detected in the state’s south, as was a wheat leaf rust pathotype (76-1,3,5,7,9,10,12 +Lr37), which had spread from the eastern states.

All these changes in the pathogenicity and distribution of rust diseases highlight the need for a vigilant approach to rust control.

If growers decide to plant susceptible or very-susceptible varieties, fungicide treatment of seed or fertiliser, or an in-furrow fungicide application at planting, are required. A plan for follow-up foliar fungicide applications is also critical.

Moderately resistant/moderately susceptible (MR-MS) and moderately susceptible (MS) varieties may require fungicide treatments at planting and/or foliar fungicide spraying later in the season depending on the level of disease pressure.

If you choose resistant (R) or moderately resistant (MR) varieties, fungicide applications at planting are not generally required. However, no matter which variety is chosen, growers are advised to carefully monitor crops for rust diseases to optimise the timing of fungicide applications and assist with the detection of new pathotypes.

Growers are encouraged to send rust-infected plant samples for testing to the PBI’s Australian Cereal Rust Survey, Private Bag 4011, Narellan NSW 2567, which is a free service funded by the GRDC.


More information:

Dr Will Cuddy,
02 9351 8871,

will.cuddy@dpi.nsw.gov.au;

Professor Robert Park,
02 9351 8806,
robert.park@sydney.edu.au;

www.rustbust.com.au

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