Trials were carried out in Gibson and Wongan Hills in 2015, with Grains Research and Development Corporation (GRDC) investment, by Department of Primary Industries and Regional Development (DPIRD) researchers. These found medium to high levels of RLN at the beginning of the season led to canola yield losses of up to 21 and 22 per cent in triazine tolerant (TT) varieties from the nematode species Pratylenchus quasitereoides and P. neglectus, respectively.
The average yield loss from RLN across the five TT varieties sown at these trial sites was 16%. But further testing is needed to confirm the level of economic losses these nematodes can cause in canola crops in WA.
DPIRD Agriculture and Food senior nematologist Dr Sarah Collins said while symptoms of P. neglectus or P. quasitereoides have not been noted in canola rotations on-farm, they are visible in cereals.
She said it was valuable to monitor paddocks with cereal/canola rotations that don't perform to expectation for potential RLN damage this winter and test suspect paddocks.
"Knowing RLN presence and incidence levels in 2017 will help to manage this pest through future rotation planning," she said.
SIGNS AND TESTING SERVICES FOR RLN
Due to lack of in-paddock symptoms, it is difficult to diagnose canola crops affected by RLN. Growers can access more information about nematode signs and diagnosis on DPIRD's MyCrop website hub by click HERE.
Dr Collins said sending soil or plant root samples from suspect areas to a testing service is the only way to identify the RLN species (or other root/hypocotyl diseases) that are present in the paddock and the incidence level.
She explains how to best take soil samples for nematode testing on the YouTube video ‘Root Lesion Nematodes' that can be found HERE.
For in-season testing, soil and plant root samples are sent direct to DPIRD Diagnostic Laboratory Services Plant Pathology (formerly AGWEST Plant Laboratories). For more information click HERE.
National PREDICTA® B testing shows RLN is now the second most important soil/stubble-borne disease in Australia. The biggest growth in demand for this testing service is coming from the western and northern regions. For more information about PREDICTA® B click HERE.
RLN RESISTANCE AND TOLERANCE
Previous research in WA has found canola crops increase RLN levels (plants are susceptible) and yields are reduced (plants are intolerant) by both P. neglectus and P. quasitereoides.
Dr Collins said this means canola - which can be an effective option to reduce levels of some other soil-borne diseases that are significant in WA (such as rhizoctonia and take-all) is not behaving as a break crop for RLN.
She said it can potentially make the situation worse and this reinforces the benefit of knowing the specific cause of patchy growth or under-performing areas in the paddock. For example in the 2015 trial at the DPIRD Wongan Hills Research Station, the five varieties of canola sown (as well as wheat and barley crops) were susceptible and intolerant to the RLN species P. neglectus.
Dr Collins said key findings from this site included:
- All canola varieties sustained significant yield loss under high P. neglectus pressure,
- Average yield losses were 16%, in a range of 11-21%,
- Stingray was the highest yielding variety where RLN levels were low,
- Stingray was the most intolerant variety, with yields falling by 0.59 tonnes per hectare under high P. neglectus levels,
- Snapper had the highest yields (2.38t/ha) where RLN levels were high,
- Cobbler was the most tolerant variety tested, with yields falling only 11% (0.27t/ha) where RLN levels were high.
As shown in figure 1, all canola varieties lost yield where levels of WA's most common RLN (P. neglectus) were high.
GRDC Project Code: DAV00128
More information:
Dr Sarah Collins, DAFWA
08 9368 3612
