Moisture stress leads to crown rot

Jo FulwoodThe West Australian

Crown rot will only have an impact on cereal crop yields during times of moisture stress at grain filling.

Department of Agriculture and Food WA development officer Greg Shea told the Regional Crop Updates in Cunderdin recently that the pathogen had been found across the Wheatbelt.

Mr Shea said survey data from the past four years collected by the Grains Research and Development Corporation-funded Focus Paddock project had also shown that inoculum levels were increasing.

He said the key to reducing the yield impact of crown rot was matching the maturity of varieties to the length of the growing season to minimise the risk of water stress during the grain fill stage.

"If your crops don't get stressed at the end of the season, you can have the fungus in the crop without it making an impact on yield," Mr Shea said.

He said the first discovery of the disease in WA had been in the 1920s, but with the increase in minimum tillage systems and continuous cropping, the disease had become more prevalent in recent years.

"When the fungus expresses itself in the plant, we are seeing yield losses of up to half a tonne," he said.

"In simple terms, it just makes the drought worse."

Mr Shea said the fungus invaded the stem of the plant, chocking its ability to draw moisture and nutrients into the head of the plant.

He said crown rot had flourished in paddocks where long-term no-tillage practices had been applied to multiple cereal rotations, coupled with reduced stubble burning.

"Farmers have been doing the right thing and keeping their stubble to protect their soil over the summer break, employing minimum-tillage practices during seeding," he said.

"Unfortunately, this has set many paddocks up to host the pathogen and encourages the levels of crown rot inoculum."

The most susceptible paddocks were those in a continuous cereal rotation, such as wheat on wheat or wheat on barley.

Mr Shea said break crops such as canola were critical in managing the disease.

"The pathogen is contained in the stubble, and new plants are only infected when they are physically touching an infected piece of stubble," he said.

Mr Shea said growers could also other ways to control the spread of the fungus were to use a registered fungicide seed dressing, or to plant off the row to move the new plants away from infected stubble.

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