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Wednesday, 28 December 2016 11:02

Nematode watch

Knowing which nematode species or root disease is present in a paddock - and at what levels - is important to help fine-tune crop rotation and variety decisions for 2017 to help break pest and disease cycles.

Department of Agriculture and Food researcher Sarah Collins conducts nematode research funded by the Grains Research and Development Corporation.
She said that if nematodes were suspected, it was advisable to correctly identify the cause and make a plan for next season - as there were few options for in-crop management.
“Patches in paddocks, increased weeds, uneven and stunted plant growth, yellowing of plants and wilting or death under water stress - particularly at flowering and grain fill stages - can indicate the presence of root disorders in crops,” Dr Collins said. 
“However, correct identification of root lesion nematodes – the main nematode species affecting crops - as well as common root diseases, like rhizoctonia and take-all, can be achieved by soil testing, coupled with visual assessment of the root and hypocotyl of affected plants.
”Dr Collins said the incidence of RLN was increasing across the grainbelt and GRDC-funded research by DAFWA as part of a ‘Focus Paddock’ project (which was completed in 2015) indicated 5.54 million hectares of WA’s cropped area were infested with RLN.
Surveys in recent years have shown that 50 per cent of paddocks across WA’s grainbelt have medium to high risk of up to 50 per cent yield loss due to RLN damage.  
“Reports from the field in 2016 were that RLN continued to be damaging in the last cropping season and advisers have identified this pest as a major cropping issue,” Dr Collins said.
She said soil testing and monitoring could be conducted year-round through the South Australian Research and Development Institute (SARDI) PreDicta B® service. 
The quality of results can be assured by sampling in the row of the previous season’s crop, keeping samples at room temperature and sending samples to SARDI within two weeks of collection.
Plant and soil testing and monitoring can be carried out through DAFWA’s Diagnostic Laboratory Services - Plant Pathology to help to correctly diagnose, monitor and manage nematodes and root and hypocotyl diseases in a range of crops.
“However, DDLS must check for RLN in-season as, during summer, the nematodes desiccate and DDLS  testing protocols rely on the presence of active nematodes,” Dr Collins said.
She said that when considering crop sequences for next year, lupins could be a good management tool for reducing the nematode species Pratylenchus neglectus and P. quasitereoides. 
“But lupins are very susceptible to damage from P. penetrans, highlighting the importance of correct species identification,” Dr Collins said.
“DAFWA research also shows that liming of soils with low pH levels is another important tool to ameliorate potential RLN damage.  
“Controlling weeds and volunteers pre-season can also help to reduce plant parasitic nematode levels.”Dr Collins said using resistant or tolerant crop varieties or non-host break crops and pastures could help to inhibit RLN reproduction and build up (resistance) and potentially boost crop yields to non-limiting levels under RLN pressure (tolerance).

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