‘Soil test and save’ is the message being delivered to northern grain growers in the lead up to the winter cropping season following concerns that root lesion nematodes (RLN) could cost the industry millions of dollars in yield.
A Grains Research and Development Corporation (GRDC) supported project ‘Genetic options for Nematode Control’ led by Professor John Thompson and Jason Sheedy of University of Southern Queensland (USQ) surveyed 600 paddocks between 2010 and 2013 and found that RLN populations of above 2 nematodes/g soil (2000/kg soil) were present in 50% of the paddocks.
These results send a clear signal to growers that baseline measurement and management of RLN populations through soil testing, varietal selection and crop rotation is imperative if yield losses are to be avoided.
The DNA-based soil testing service PreDicta B® offered through the South Australian Research and Development Institute (SARDI) provides an indicator of RLN populations for growers and should be used prior to planting to establish whether crops are at risk and if alternative crop types or varieties should be grown.
Soil sampling for a PreDicta B® test to determine RLN levels can be arranged by contacting commercial testing service, Crown Analytical Services, which provides northern growers and advisors with bags, soil corers, protocols and procedures for sampling as well as an interpretation of results once tests are completed.
USQ crop nematologist Dr Kirsty Owen said soil tests would determine which species of RLN is present (Pratylenchus thornei and/or P. neglectus), measure the population density and allow for the monitoring of population changes in rotations.
“If RLN are not detected, protect those paddocks from contamination by controlling movement of soil and water on the farm,” she said.
“Clean soil from machinery before planting or fertilising and plant RLN-free paddocks first. Consider re-testing in 5 years, particularly if there has been flooding, because RLN can move in floodwaters and in soil.”
In paddocks where RLN populations are detected, Dr Owen said rotation and variety selection were the primary management options and that growers should aim to reduce populations to less than 2 nematodes/g soil (2000/kg soil).
“When very high populations of RLN are detected, it may take two or more resistant crops grown consecutively in rotation to reduce populations,” she said.
“Re-testing of soil after growing resistant crops is recommended so that crop sequences can be adjusted if populations are still at damaging levels. It’s also extremely important to avoid very susceptible crops and varieties.”
RLNs are microscopic worm-like animals that move between soil pores towards plant root systems. They use their head and a syringe-like stylet in their mouthpart to break open cell walls. They enter the plant roots and feed on the contents of root cells. The damage they cause restricts the plant’s ability to uptake water and nutrients, leading to yield loss.
Intensive cropping of susceptible crops, particularly wheat, will lead to an increase in P. thornei and P. neglectus levels in the soil and studies have shown that the extent of yield loss from RLNs is directly related to the populations present at planting.
In the northern cropping regions, P. thornei at 2 nematodes/g soil (equivalent to 2000/kg soil) anywhere in the soil profile is considered a damaging population, causing yield loss of up to 70% in wheat and 20% in chickpeas.
“Those growers looking to plant wheat need to consult the latest National Variety Trial data which is available online at www.nvtonline.com.au, look at the tolerance and resistance ratings and select the most tolerant and resistant variety for the particular nematode species present in the soil,” Dr Owen said.
“When it comes to planning rotations, avoid consecutive susceptible crops to limit the build-up of RLN populations. Choose rotation crops with high resistance ratings, so that fewer nematodes remain in the soil to infect subsequent crops.”
More information on the PreDicta B® tests is available on the SARDI website and by contacting Crown Analytical Services on 0437 996 678.
Caption: USQ crop nematologist Dr Kirsty Owen says soil tests help determine which species of root lesion nematodes is present, measure the population density and allow for the monitoring of population changes in rotations.
Dr Kirsty Owen, crop nematologist, USQ
07 4639 8805
Sarah Jeffrey, Cox Inall Communications
0418 152 859
GRDC Project Code