ENTOMOLOGISTS have reported a further spread in populations of green peach aphid (GPA) with resistance to neo-nicotinoid insecticides.
The resistance to the insecticide group is not new, but the industry is concerned about the spread of resistant GPA populations, which are now found in all major grain producing regions.
Neo-nicotinoid seed treatments are a particularly important method of controlling predators of newly emerging crops, such as aphids and red legged earth mite, especially in pulse and canola crops.
Resistance to neonicotinoids has been detected in a number of new populations collected from the major grain growing regions of Western Australia, Queensland, New South Wales and Victoria in research undertaken on behalf of the Grains Research and Development Corporation (GRDC) in 2017.
GPA is a widespread pest of canola and a range of pulse crops, transmitting viruses including turnip yellows virus, and causing damage by feeding when in high numbers.
It has confirmed resistance to four different chemical mode of action groups – synthetic pyrethroids, carbamates, organophosphates and neonicotinoids.
Paul Umina, director of Melbourne-based scientific research organisation cesar, says recent testing confirms the importance of growers using integrated pest management practices.
“Resistance to neonicotinoids in GPA is not new, but it is concerning that resistance has now spread to all of Australia’s major grain growing regions,” Dr Umina said.
He said growers now needed to make sure they assessed their risks prior to planting to prevent the chance of serious crop damage whether through viruses or feeding.
“Due to the high risk of further resistance developing, it is recommended that, wherever possible, growers assess the risk of damaging infestations or virus risks prior to making management decisions,” Dr Umina said.
In terms of long-term rotations, he said giving the paddock a spell from the use of neo-nics was critical.
“Unless the risk of feeding damage or virus transmission is deemed high, avoid using neonicotinoid seed treatments in the same paddock over consecutive years.”
“High risk situations for GPA are considered early sown crops, paddocks containing brassica weeds and/or volunteer canola, and/or regions with a history of outbreaks of viruses such as turnip yellows virus.”
He also urged growers to avoid at all cost putting out a prophylactic ‘insurance’ spray if numbers were not assessed as being at damaging levels.
While at present it is not expected the resistance will lead to 100 per cent insecticide failure, cesar is also monitoring for incursions of exotic strains of GPA that have much stronger resistance.
“There is biotype of green peach aphid overseas that cannot be controlled with neonicotinoids,” he said.
“It has never been detected in Australia, but we are monitoring for it just in case.”
But it is not all bad news on the insect management front.
The dry conditions that have plagued Australia this autumn have a silver lining in that they have reduced the risk of damaging GPA populations developing.