Resistance to neonicotinoid insecticides has for the first time been confirmed in Australian populations of green peach aphid, a serious broadacre cropping pest.
The discovery means GPA is known to have resistance to four different chemical mode of action groups: synthetic pyrethroids, carbamates, organophosphates and now, neonicotinoids.
GPA is a widespread pest of canola and a range of pulse crops, causing damage by feeding and transmitting viruses, including beet western yellows virus which decimated canola crops in parts of South Australia, Victoria and NSW in 2014.
It is also a common pest in horticulture.
Resistance to neonicotinoid insecticides , commonly used in the grains industry in seed treatments, was recently confirmed by scientists involved in research undertaken on behalf of the Grains Research and Development Corporation and Horticulture Innovation Australia.
The work has been led by Melbourne-based scientific research organisation cesar, in collaboration with researchers at CSIRO.
Cesar entomologist Paul Umina said resistance to neonicotinoids had been confirmed in a number of GPA populations across Australia.
Specimens taken from canola and vegetable crops tested positive for resistance.
Dr Umina said the discovery underlined the need for sound management resistance strategies and integrated pest management practices to ensure long-term access to available chemistries.
‘‘Our findings don’t mean that neonicotinoids are dead in the water; they are still a valuable tool,’’ Dr Umina said.
‘‘But the discovery does serve as a reminder that all chemicals are vulnerable to resistance development, particularly when dealing with a species like GPA which is known to have a high propensity to develop insecticide resistance.’’
The mechanism underlying neonicotinoid resistance in Australian GPA populations has been identified as metabolic resistance which, fortunately, means that functionally resistance levels are low to moderate.
Dr Umina said there was another mechanism conferring neonicotinoid resistance in GPA, which leads to a very high level of resistance, and complete field failures.
‘‘In good news, this high-level resistance, which is found overseas, hasn’t been detected in Australia,’’ he said.
‘‘By adopting resistance management strategies, we can significantly reduce the likelihood of this resistance evolving in Australian GPA.’’
Dr Umina said Transform, a sulfoxaflor foliar insecticide, remained an effective means to control GPA in canola crops.
Siobhan de Little, a senior consultant with cesar, said it took researchers some time to establish the methodologies necessary to confirm resistance to neonicotinoids.
‘‘We used a relatively new laboratory-based methodology in combination with genetic testing to confirm aphid populations were in fact resistant,’’ Dr de Little said.
‘‘But it is not a discovery in isolation when you consider it in the context of what we already know in terms of GPA and its resistance to other chemical groups.’’
GPA has high levels of resistance to pyrethroids and carbamates, and while resistance to organophosphates is broad across Australia, levels of resistance to this group are lower.
Insecticide resistance almost always evolves due to the over-reliance on a particular chemical leading to strong selection.
■Growers are encouraged to follow the GPA Resistance Management Strategy, at: www.grdc.com.au/GPAResistanceStrategy
■If aphids are seen surviving on young canola plants that have been treated with neonicotinoid insecticide seed treatments, growers are urged to phone cesar on 93494723.