Central and northern NSW and southern Queensland, Australia
March 30, 2015

By GRDC Northern Region Panellist Keith Harris

Crown rot is likely to rear its head once again this year however growers can minimise its impact on yield potential by undertaking a paddock disease assessment prior to planting, selecting appropriate varieties and knowing seed purity. 

Crown rot is caused by the fungus Fusarium pseudograminearum and is one of the most serious disease threats to winter cereal crops in Australia.

It is widespread in wheat, barley and durum paddocks in central and northern NSW and southern Queensland and can have a serious impact on yields.

Over the years trials have shown that with high infection, yield losses can be more than 50% but importantly, even at low inoculum levels, you can still get yield losses of 25% if the season runs against you.

The DNA-based soil testing service PreDicta B® is a reliable medium for identifying the level of risk for crown rot and other soil-borne pathogens prior to sowing but it is important to remember that using the correct sampling technique is critical to its accuracy. It isn’t a simple add-on to a soil nutrition test.

The Grains Research and Development Corporation (GRDC) and South Australian Research and Development Institute (SARDI) recommend adding short pieces of stubble from the base of cereal plants (‘spiking’) to significantly improve the detection of the Fusarium species that cause crown rot.

Soil cores should be targeted at the previous winter cereal row if evident and retain any stubble fragments. Detailed information on crown rot and sampling protocols can be found by visiting www.extensionaus.com.au.

Once the level of crown rot risk for individual paddocks is determined, growers can select crop varieties that will allow for optimal production.

Certain cereal varieties are more prone to crown rot than others and it’s imperative that growers are aware of the crown rot rating of the variety they intend to plant.

Awareness of seed purity is similarly important and unfortunately many growers are still unsure of the purity of their seed.

Too often there has been a contamination issue in the paddock, header, bins, trucks or silos which has resulted in costly losses due to the wrong variety being planted.

Purchasing new seed is cheap insurance if growers are unsure of the purity of their seed source as losses of even 25% at harvest time are disastrous.

The GRDC-funded National Variety Trial (NVT) results highlight the latest disease ratings of various cereal varieties and this information is readily available from the NVT website www.nvtonline.com.au.

Speaking at the recent GRDC Grains Research Updates in Goondiwindi, Rob Long from B&W Rural and Crown Analytical Services echoed the call for growers and advisors to do their due diligence prior to planting to ensure optimal variety selection and allow for the implementation of an effective and integrated agronomic management program.

He said where possible growers/advisors should consider objective measurements including inoculum level  (measured by CR Index using stubble or Predicta B® using soil + stubble spikes); amount of stubble and therefore potential volume of inoculum; root lesion nematode numbers (interaction with crown rot); starting soil water (measured in mm or %PAWC); soil nitrate levels; as well as factors that affect soil hydraulic conductivity and water supply during grain fill (such as soil clay% - particle size analysis, soil bulk density, soil sodicity and soil EC).

Prevention is almost always better than a cure and good pre-plant planning can go a long way to ensuring that this winter crop is as productive and profitable as possible.

 

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

Published: March 30, 2015