Australia
September 1, 2012

Testing soil for root-lesion nematode type and population during the summer cropping phase is a crucial step in ensuring follow-up wheat and chickpea crops can achieve their maximum yield potential.

That's the message from Dr Kirsty Owen, Agri-Science Queensland soil microbiologist who says more than 2000 nematodes per kilogram anywhere in the soil profile equates to a potentially damaging population.

"This means at least two resistant crops must be grown after a susceptible crop to decrease numbers to give wheat and chickpea crops a chance to achieve maximum yield potential," Dr Owen said.

She says the main root-lesion nematode species in the Grains Research and Development Corporation (GRDC) northern region are Pratylenchus thornei and Pratylenchus neglectus. They can reduce yields of intolerant varieties by more than 50 per cent in wheat and up to 20pc in chickpeas.

"Root-lesion nematodes are a significant problem that cost northern-region growers $47 million a year in lost wheat production," Dr Owen said.

Most summer-crop varieties are nematode-tolerant, meaning they will grow well when root-lesion nematodes are present. However some varieties are susceptible and will increase nematode numbers.

"Summer crops with resistance to root-lesion nematodes offer a means of reducing populations but only when you know which species of root-lesion nematode is present," she said.

Of the 150 fields tested by Agri-Science Queensland's nematode testing service in the region this year, 64pc of fields had potentially damaging levels of root-lesion nematodes and only 11pc of fields were nematode free.

"Determining the species of nematode you have is crucial so you can choose the most suitable crop and variety to use in your rotation," Dr Owen said.

"For example, sorghum is resistant to P. thornei but susceptible to P. neglectus, so when sorghum is grown in a field infested with P. thornei, nematode populations will decrease.

"In contrast, when sorghum is grown in a field infested with P. neglectus, populations of this nematode will increase, leaving more nematodes in the soil to attack future intolerant crops.

"Most varieties of mungbeans, while susceptible to P. thornei, are beneficial to plant into high populations of P. neglectus because they are resistant.

"Soybeans, cowpeas and navy beans are all susceptible to P. thornei but resistant to P. neglectus, while sunflowers are resistant to both species."

Because nematodes are microscopic, the identification of root-lesion nematodes can only be done in a laboratory.

Soil can be collected at any time - in-crop or before planting. Agri-Science Queensland offers a "Test your farm for nematodes" service for a fee. Details on how to sample a field and where to send soil are available at www.deedi.qld.gov.au (search "nematodes").

Information about which varieties of wheat are resistant and tolerant to nematodes is available on GRDC's www.nvtonline.com.au website.
 

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

Published: September 1, 2012