Australia
April 4, 2016

DAFWA nematologist Sarah Collins says it is important to correctly identify the species of nematodes present in paddocks due to differences in the susceptibility of break crops and varieties to different RLN.

Western Australian growers are encouraged to undertake soil testing from paddocks suspected of having root lesion nematode (RLN) damage in 2015 in order to help plan future rotations and varieties.

This follows unprecedented numbers of the microscopic pest recorded by Department of Agriculture and Food (DAFWA) researchers in parts of the WA grainbelt last year.

Soil testing prior to sowing enables identification of the species of nematode present, which is important as there are differences in the susceptibility of break crops and varieties to different RLN species.

DAFWA nematologist Sarah Collins, who is conducting Grains Research and Development Corporation (GRDC) funded research into RLN, said numbers previously thought impossible in WA were recorded at a Wongan Hills trial site in 2015.

In addition, a targeted DAFWA survey of 31 paddocks across the grainbelt found that 23 had potentially yield-limiting populations.

“What remains uncertain is whether RLN damage spiked last year in WA on the back of crops being moisture stressed at the end of the season, or whether numbers will keep rising in 2016,” Dr Collins said.

“However, surveying of RLN through the Focus Paddock project has shown numbers of these microscopic endoparasites have been increasing right across the WA grainbelt for the past five years at least.”

Dr Collins said the common RLNs found in WA were P. neglectus, P. quasitereoides (formerly known as P. teres) and P. thornei. P. penetrans is rare but can be highly damaging when present.

“There are limited in-crop options for preventing damage from nematodes,” she said.

“After species identification, management hinges on crop and variety choice for the coming season and beyond. The goal is to break the pest cycle.”

Dr Collins said a run of seasons favourable to RLN and increasing use of canola in crop rotations were likely to be contributing to rising nematode numbers across much of the State.

“The host range for root lesion nematodes is broad and includes cereals, oilseeds, grain legumes, pastures and many broadleaf and grass weeds,” she said.

“However, well-managed rotations can minimise the damage caused to cereal production.”

Dr Collins said that in DAFWA’s nematology group field trials in 2015, all wheat, barley and canola crops were susceptible to P. neglectus, P. quasitereoides and P. penetrans.

Lupins were resistant in all P. neglectus and P. quasitereoides trials, but proved highly susceptible to P. penetrans.

DAFWA is in the process of analysing 2015 trial data to determine RLN impacts on crop yield, and is conducting further trials to help improve understanding of yield impacts for these crops.

“Preliminary results from 2015 trials show there was yield loss for wheat, barley and canola crops, but the degree of loss differed with location,” Dr Collins said.

At a DAFWA trial at Gibson, yields were significantly impacted by P. quasitereoides in all five varieties tested, with losses of 10 to 65 per cent. 2015 trials represent the first time that canola has been tested for RLN tolerance in WA and further experiments will be conducted.

As outlined in the GRDC’s Wheat GrowNotes for the western region (www.grdc.com.au/GrowNotes), RLN management includes:

• Planning crop rotations with resistant or non-host break crops and resistant pastures
• Using crop varieties that are resistant or tolerant to the RLN species in the paddock
• If RLN levels are high to very high, considering growing a moderately resistant
  (MR) or resistant (R) crop or pasture for one or more seasons
• Avoiding sowing consecutive susceptible crops across seasons
• Maintaining healthy soils and good crop nutrition, especially at crop establishment
• Controlling weed and crop volunteers over summer as they may build up RLN populations
• In the lead-up to and around harvest, monitoring cereal crops for potential damage

The GRDC is funding a nationally-coordinated nematode research program to quantify the yield and economic impacts of RLN in crop production systems.

Soil testing for confirmation of nematodes and species identification can be carried out by AGWEST Plant Laboratories (APL), with further information available at www.agric.wa.gov.au/agwest-plant-laboratories, or by accredited agronomists through SARDI’s PreDicta B® service.

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

Published: April 4, 2016