sustainability through science & innovation

Insecticide resistance in the green peach aphid – where are we after 4 years of surveillance?

21 Oct 2019

If you google ‘green peach aphid’, you’re more than likely to see us, cesar, in your search feed.

If you google ‘green peach aphid insecticide resistance’, there is just no avoiding knocking on our web door.

Why?

We have had a lot to say about green peach aphid (Myzus persicae) over the past five years. This infamous aphid has been front and centre of the GRDC-funded project ‘Aphid and Insecticide Resistance Management in Oilseed and Pulse Crops’, which our researchers at cesar have been working on since 2015.

With the project coming to a close in June 2019, let’s take a look three major findings from this project – they are relevant to all broadacre growers and advisers in Australia.

 

1. Green peach aphid exhibits some level of insecticide resistance to all five registered insecticide mode of action (MoA) groups in grains

There are currently five insecticide MoA groups registered to control green peach aphid in grains: carbamates, pyrethroids, organophosphates, neonicotinoids and sulfoximines.

Prior to the project starting in 2014, through our previous field survey work we already knew that green peach aphid was highly resistant to pyrethroids and carbamates, rendering these two MoA groups ineffective for control. We also already knew that green peach aphid was moderately resistant to organophosphates, which provides control in some situations, but less or no control in others.

Knowing green peach aphid’s reputation for evolving insecticide resistance, with the help of growers and advisers all over Australia (thank you!), we collected and ascertained the resistance profile of over 450 green peach aphid populations from 2014-2019.

Not only did we find continued prevalence of synthetic pyrethroid, carbamate and organophosphate resistance across Australia, we showed that most green peach aphid populations collected from grain crops in Australia now have low-level resistance to neonicotinoids. This important finding indicates that the length of protection provided by neonicotinoid seed treatments against green peach aphid is likely to be lessened.

Project surveillance also led us to detect the first signs of low-level resistance evolving to sulfoxaflor (Transform™) in isolated Western Australian green peach aphid populations.

 

Insecticide resistance status for carbamates, pyrethroids, organophosphates and neonicotinoids in tested green peach aphid populations in Australia.

2. Attack of the super clones

While the term ‘green peach aphid’ refers to a single aphid species ‘Myzus persicae’, there are genetic difference between populations (different ‘clone specific’ make-ups). This project allowed our team to build on our previous work investigating the clonal make-up of green peach aphid populations across different regions of Australia.

We found that within Australia, green peach aphid populations are dominated by three super-clones across all seasons in broadacre and horticulture cropping regions in Queensland, New South Wales, Victoria, South Australia, Western Australia and Tasmania. And crucially, they all carry some level of resistance to synthetic pyrethroids, carbamates, organophosphates and neonicotinoids.

Our results suggest that if you have found green peach aphid in a crop, it is reasonable to assume that it is a resistant type.

 

3. We didn’t detect the worst of the known green peach aphid mutants!

Overseas some green peach aphid have evolved a mutation known as R81T. Currently only detected in Europe, northern Africa and parts of Asia, this mutation is bad news as it causes high-level resistance to neonicotinoids and results in complete control failures in the field when using this MoA group. Moreover, this mutation will almost certainly be accompanied with intermediate level resistance to sulfoxamines (e.g. Transform™).

Recognising the adverse impact that it would have on oilseed crops if the mutation were to arrive or evolve in Australia, we developed a novel, cost-effective way to establish a national monitoring program for R81T.

Between 2018-2019, we deployed a network of 300 yellow sticky traps that were placed in horticultural crops, broadacre crops, and even urban gardens around Australia. We then developed genetic testing methods to screen for the presence of green peach aphid on sticky traps as well as for the R81T mutation.

The results?

We successfully identified green peach aphid from 60% of all traps deployed of which none tested positive for the R81T mutation, providing evidence of its absence in Australia.

 

Where to now?

While this project may have come to a close, we are not letting green peach aphid off the hook, especially since sensitivity shifts to sulfoxaflor have been detected. We are still interested in hearing about suspected control failures and efficacy issues.

If you have any questions about green peach aphid control or would like to report insecticide resistance in green peach aphid (or any other aphid), contact us via our PestFacts south-eastern service (03 9349 4723, pestfacts@cesaraustralia.com).

 

Written by Julia Severi, Research Adoption and Extension Scientist at cesar.