Russian wheat aphid in northern NSW

Russian wheat aphid has been confirmed in Coonabarabran NSW, some 400 km northeast of the last site of detection in central NSW.

 

The known distribution of Russian wheat aphid (RWA, Diuraphis noxia) in Australia has expanded after its presence was confirmed in northern NSW. The aphid was discovered in a wheat crop in Coonabarabran on the border of the Central West and North West Slopes and Plains. After discovering the suspect RWA infield, the diagnosis was confirmed by the NSW DPI at the Orange Agricultural Institute.

Prior to this detection, the most northern point where RWA was confirmed present was 20 km north of Lake Cargelligo in the NSW Central West Slopes and Plains. As Coonabarabran is several hundreds of kilometres from this area, it could be that the aphid is more widely distributed in NSW than officially known. Russian wheat aphid has a host range of more than 140 grass species, so even with far fewer winter cereals growing due to the dry conditions, there are alternative food sources available to the aphid.

Without a doubt, the symptoms of RWA are far easier to spot than the aphids themselves. When RWA feeds it introduces a toxin into the plant causing symptoms such as leaf rolling, lengthwise streaks (pale or purple), and stunting. However, not all hosts are equally as suitable for RWA production and development, and therefore symptoms may not always be obvious.

While cereals such as barley, wheat and durum are powerhouse hosts for RWA, according to literature from the United States, about 70% of known species are relatively poor hosts for RWA development. So RWA populations may travel under the radar, exploiting less suitable hosts to survive at low levels. For example, cesar researchers Dr Elia Pirtle and Dr James Maino were recently assessing roadside grasses for RWA in northern Victoria, and could only detect their presence by random vacuum sampling of foliage.

While RWA has already been declared established in NSW and is no longer a notifiable pest, the NSW Department of Primary Industries and cesar are interested in hearing about incidences in previously unreported areas. We encourage growers or advisers who suspect RWA is present in previously unreported areas to contact cesar or NSW Department of Primary Industries Biosecurity Officer, Rachel Taylor-Hukins (0409 945 069, rachel.taylor-hukins@dpi.nsw.gov.au).

For information on Russian wheat aphid including management, visit the RWA portal on the cesar website.