A SPECIALIST podcast will help growers to learn the latest about threats such as Russian Wheat Aphids (RWA).
Higher temperatures in spring may lead to an increase in aphid migration, but scientists say crops older than growth stage (GS) 40 do not appear to be attractive to migrating RWA, therefore colonisation of such advanced crops during spring is unlikely.
Rare cases of RWA presence and symptoms, below intervention thresholds, have been reported this year by growers and advisers in areas such as Victoria's southern Mallee and East Gippsland, as well as the Riverina, Central West Slopes and Plains, and the Central Tablelands.
Entomologists involved in Grains Research and Development Corporation (GRDC) research investments say economically significant yield impacts are more likely from infestations that occur before stem elongation, but only if these persist during the later (heading and flowering) stages.
Maarten van Helden, an entomologist with the South Australian Research and Development Institute (SARDI), the research division of Primary Industries and Regions SA, says detecting RWA in crops is not difficult as indications of infestation are usually quite obvious.
"A tell-tale sign is white or purple leaf streaking in cereal crops," says Dr van Helden. "And at late tillering and during stem elongation, leaf rolling may occur."
Dr van Helden shows plants with typical symptoms of Russian wheat aphid infestation, such as leaf streaking. Photo: GRDC
Growers should search for the presence of aphids by peeling back rolled leaves, since symptomatic tillers do not always contain aphids and therefore treatment may not be required if the aphids have either moved on or died.
First identified in Australia in 2016, RWA is now present in many cropping areas of South Australia, Victoria, Tasmania and NSW. The aphid has not been detected in Western Australia, the Northern Territory and Queensland.
Since RWA has only been confirmed in Australia in recent years, limited research under local agro-climatic conditions and farming systems has been conducted.