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Growers Need Strategy to Manage Yellow Leaf Spot

25 April 2011

AUSTRALIA - Southern Riverina and north-east Victorian grain growers will need to develop a strategy to manage yellow leaf spot before they plant this season's wheat crop, according to a cereal diseases authority.

Greg Platz, Principal Pathologist, Agri-Science Queensland, advised the audience at a recent Grains Research and Development Corporation (GRDC) Grower Update at Corowa, NSW, that yellow leaf spot posed a risk to susceptible wheat varieties, writes Stock & Land.

He said the fungus, which survives in crop residue and is favoured by frequent and extended periods of wet weather and temperatures between 10 and 30°C, is best treated through reducing infected stubble.

"When the new crop is sown into infected stubble and wet conditions prevail, mature ascospores are ejected onto the new crop and infection occurs," Platz said.

If the infection is left untreated, a susceptible wheat variety may measure yield losses of up to 65 per cent, Platz said.

Triticale and rye are also susceptible to yellow spot.

In current farming systems, the emphasis has been on maximum retention of surface stubble, a system which also works in the favour of yellow leaf spot development, according to Platz.

"With stubble retention it is a matter of when and not if yellow spot will become a problem."

Continuous cultivation of wheat-on-wheat will lead to losses from yellow spot whenever favourable environmental conditions occur, Platz said.

Mr Platz told the audience no control option was 100 per cent effective in a wheat-on-wheat system, but there were resistant wheat varieties available.

Hartog and Banks have proved low levels of resistance do produce a yield benefit.

Under similar epidemic conditions, sprayed plots of Hartog yielded 57pc higher than the unsprayed control while the sprayed Banks increased yield by 146pc.

Fungicide success will be directly related to application number and timeliness, Mr Platz said, with maximum yield and quality benefits obtained by keeping the upper leaves free from disease during grain fill.

TheCropSite News Desk

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