Barley growers have been urged to include strategies to minimise the impact of Spot type net blotch (STNB) on their crops, as occurrences of the fungal disease continues to rise.
Data illustrating the impact of the disease will be presented to the 2016 GRDC Grains Research Update, Perth later this month.
Department of Agriculture and Food research officer Andrea Hills said Cooperative Bulk Handling’s (CBH) figures showed that more than 98 per cent of the Western Australian barley crop was rated as susceptible or worse to STNB. (See Fig 1.)
Ms Hills said the increase was consistent with the widespread adoption of Hindmarsh and other susceptible varieties and a trend in the central region towards cropping barley on barley.
"Crop vulnerability to STNB is a function of variety, paddock rotation and rainfall zone,” she said.
“Varieties such as Hindmarsh and La Trobe are at the highest risk, while crops grown on barley residues or downwind of infected stubble are likely to suffer an ongoing barrage of infectious spores.
“Spot type net blotch increases and spreads with rainfall so medium to high rainfall areas are generally at most risk of significant yield impacts.”
Although new lines with improved STNB resistance are being developed, they are not expected to be available for another three to five years.
Ms Hills said until then, integrated management strategies were imperative to maximise barley yields and quality.
“Selecting a variety with disease resistance is normally the best way to combat any disease, however, the feed variety Fathom is the only current line with effective levels of resistance,” she said.
“STNB is carried by stubble, so growers should be mindful of crop rotations and avoid barley-on-barley rotations where possible.”
While a number of fungicides are available at a range of prices to control STNB, Ms Hills warned growers to evaluate their risk carefully and to budget accordingly.
“The risk of yield losses from STNB and management responses will depend on growers’ location, their crop’s yield potential and the forecast for spring rainfall,” she said.
“In low rainfall areas with a low risk of STNB facing a dry spring, growers may choose to apply a single, low cost fungicide treatment from stem elongation up to head emergence (growth stage Z31-Z55) on infected susceptible or very susceptible varieties.
“If spring rainfall, particularly September, is average or better there is likely to be an additional benefit from applying a second fungicide around three to four weeks after the first treatment.
“Growers in high disease scenarios in medium to high rainfall areas should consider two applications of a fungicide to infected crops, with the first at stem extension growth stage and the second between flag and head emergence – especially if their crop has good yield potential. In those environments it’s important to consider what other foliar diseases may be present when selecting which fungicide to apply.”
Although STNB typically causes yield losses of up to 30pc, grain quality can also be significantly affected by reduced grain plumpness, which can result in malting varieties being downgraded.
Fungicide treatments have shown to decrease screenings by more than a third.
Ms Hills said growers should weigh up the cost of treatment against potential crop profits.
“Growers with malting varieties or food varieties, like La Trobe and Hindmarsh, should also consider the benefits of treating to protect the crop’s premium,” she said.
The department’s research was undertaken with the support of the GRDC’s Improving grower surveillance, management, epidemiology, knowledge and tools to manage crop disease project.
To view the paper visit giwa.org.au and more information about treating for STNB is available at the department website by searching for ‘spot type net blotch’.
Media contacts: Jodie Thomson/Megan Broad, media liaison +61 (0)8 9368 3937