Neonicotinoid resistance in the green peach aphid: an update

Further cases of neonicotinoid resistance in the green peach aphid have been detected across Australia.

Since we first reported on the detection of neonicotinoid resistance in Australian green peach aphid (GPA) in 2016, further populations were tested for resistance in 2017, and unfortunately, the news isn’t positive.

Through work led by cesar researchers, Dr Siobhan de Little and Dr Paul Umina, and in collaboration with CSIRO, resistance to neonicotinoids has been detected in five of six new populations collected from WA, QLD, NSW, and VIC. This demonstrates resistance to neonicotinoids continues to worsen in Australian GPA populations.

Figure 1. The coloured dots represent all aphid populations tested for resistance to neonicotinoids (2014-2017*). Red dots signify aphid populations with resistance. Green dots signify aphid populations that, at the time of testing, did not display neonicotinoid resistance (source: cesar).

 

However, the situation is not all doom and gloom. The latest research shows that the level of resistance within GPA remains low. That is, the type of resistance is metabolic and not target-site. So, we don’t expect growers will experience complete control failures or even a dramatic loss of efficacy of neonicotinoid seed treatments at this stage.

But there is no room for complacency. Target-site resistance can develop in GPA (it has happened overseas). It is crucial that target-site resistance to neonicotinoids does not develop as it would give GPA cross-resistance to sulfoxaflor (Transform^®) and render neonicotinoids completely ineffective.

During the winter-cropping season, GPA is mostly problematic in canola and pulse crops during autumn and early winter, where it can transfer plant viruses, and also inflict direct feeding damage when present in high numbers. Due to the high risk of further resistance development in GPA, it is recommended that wherever possible, growers assess the risk of damaging infestations (or virus risk) prior to making management decisions.

High-risk situations for GPA include:

• Early sown crops
• Paddocks containing brassica weeds and or volunteer canola
• Regions with a history of virus outbreaks, such as turnip yellows virus (TuYV)

Unless the pest risk is deemed high, avoid using neonicotinoid seed treatments in consecutive years, preferably no more than 1 in 3 years in any given paddock. And don’t forget that almost all populations of GPA have a high level of resistance to synthetic pyrethroids (e.g. bifenthrin and alpha-cypermethrin) and carbamates (e.g. pirimicarb). Therefore, the use of these chemicals (even at high rates) will not provide control.

GPA are also likely to have metabolic organophosphate resistance in Australia. This mechanism is unusual because can be ‘switched on’ in response to pesticide exposure. The continued use of organophosphates is therefore risky; it could be effective in some instances but not others.

For more information see the GPA PestNote and the Resistance management strategy for the green peach aphid in Australian grains.

 

Contact information

Dr Siobhan de Little, cesar

+03 93494 723

sdelittle@cesaraustralia.com

 

*Projects were funded by GRDC (CES00001, CES00003) and Hort Innovation (VG12109)