Researchers get the dirt on nematodes in Western Australian

Western Australian（WA） growers who suspect their crops are being damaged by root lesion nematodes (RLN) can confirm which species and population levels are present in problem areas by using in-season testing services this growing season.

As RLN management methods are based on crop rotations and plant tolerance and resistance, information gained from testing will help growers adjust rotations for following years and aid research into the microscopic soil pest.

Three major RLN species cause crop damage in Western Australia (Pratylenchus neglectus, P. teres and P. penetrans).

Research being conducted by the Department of Agriculture and Food (DAFWA), supported by the Grains Research and Development Corporation (GRDC), aims to characterise differences between crop varieties in their resistance and tolerance to each species, which would allow growers to select appropriate cultivars to minimise yield losses.

Resistance refers to the effect of the plant inhibiting nematode reproduction, while tolerance is the plant’s ability to limit yield loss despite the presence of nematodes within the soil.

DAFWA researcher Sarah Collins said surveys had revealed that 5.3 million hectares of the State’s cropping zone was affected by the pest and that yield limiting levels of RLN were present in at least 40 per cent of WA crop paddocks. 

“Feeding on crop roots, RLN typically cause cereal yield losses of between 10 and 30 per cent, although losses as high as 40 to 75 per cent have been recorded,” she said.

“P. Teres, which is unique to WA and the grainbelt’s second most common RLN species, appears to be particularly damaging and our research aims to fill in knowledge gaps about this species in particular.”

Dr Collins said tell-tale signs of nematode problems included patchy or uneven crop growth, yellowing and decreased tillering during the growing season.
“To determine nematode species and levels, growers should use in-season testing services such as AGWEST Plant Laboratories, and information about this service is available under Our Services on the DAFWA website,” she said. 

“When collecting plant samples from problem areas to send to AGWEST Plant Laboratories, it is important to send the whole plants, including intact root systems and soil, as well as unaffected plants for comparison.”

Dr Collins said higher nematode populations could be present in areas which received a lot of summer rain and where there had been a ‘green bridge’ of plant material between cropping seasons.

“However, if crops receive adequate rainfall and are not under nutrient stress during the growing season, they may be better able to withstand root damage from nematodes,” she said.

Dr Collins said growers who used a testing service and confirmed that a particular RLN species was present in their paddocks could manage the pest in following seasons with well managed rotations, using resistant or non-host break crops and pastures.

“Our research – involving field testing and glasshouse trials in WA - will improve the accuracy of these rotational recommendations by characterising cultivar and crop type resistance and tolerance levels to different RLN species,” she said.

“Currently, recommendations are available relating to differences in the resistance levels of different crop types and varieties to RLN species P. neglectus.
“However, much less is known about resistance and tolerance to P. teres, which is of particular concern in WA.

“Having access to this information would allow growers to incorporate specific cultivars into rotations that limit the populations of and damage caused by nematodes.”