New insecticide resistance detected in bluegreen aphid

Summary

  • Resistance in bluegreen aphid is a rising concern in NSW and SA
  • Following new investment from AgriFutures Australia, Cesar and Lucerne Australia are investigating the extent and evolution of resistance of bluegreen aphids to commonly used insecticides
  • This research has confirmed emerging resistance to omethoate, chlorpyrifos and pirimicarb
  • Testing for resistance to alpha-cypermethrin is underway

Bluegreen aphids

Bluegreen aphids (Acyrthosiphon kondoi) are a major pest of lucerne and can also attack lupins, medics and clovers. These tiny pests feed directly on the foliage, damaging the plant and spreading harmful viruses through infected crops.

Bluegreen aphids are grey-green to blue-green coloured and can be distinguished from other aphids by their long legs, antennae and cornicles. They are widely distributed and found in all states of Australia. They are most common in spring but are also active in autumn and winter.

For more information see the PestNotes on bluegreen aphid

Bluegreen aphid photo demonstrating their long legs and antennae. Photo by Andrew Weeks, Cesar Australia

Insecticide resistance

To date, growers have had access to a limited range of insecticides to control bluegreen aphid populations. During the past two years, several growers and agronomists in New South Wales and South Australia have reported that currently registered insecticide (group 1A & 1B) sprays no longer effectively control bluegreen aphid populations.

Dr Evatt Chirgwin, Cesar Australia is leading the Understanding bluegreen aphid resistance in the pasture seeds industry project; where he is testing bluegreen aphid populations collected from key lucerne-growing regions in New South Wales and South Australia for signs of evolutionary resistance.

Previous investigations through collaborative research with CSIRO, and funded by the Grains Research Development Corporation, suggest these field populations may have evolved resistance to insecticides

Results from new research initiatives

So far, all three field-collected populations of bluegreen aphids have evolved resistance to organophosphates (omethoate and chlorpyrifos) and carbamates (pirimicarb). These field populations were collected in 2020 and 2021 after producer reported chemical control failures. Dr Chirgwin will now test for bluegreen aphid resistance to pyrethroids.

While the evolution of insecticide resistance is reasonably common in some species of crop pests, such as green peach aphids, the resistance reported in bluegreen aphids as part of this project appears to be the first of its kind in this species. The team will also be undertaking preliminary molecular work to determine how this resistance is evolving.

The project team is also keen to determine just how far resistance may have spread to get a clear understanding of the potential impact. A resistance map will be developed to understand which regions are most at risk during the coming season.

Growers experiencing issues with bluegreen aphid control are encouraged to Dr Chirgwin echirgwin@cesaraustralia.com

Bluegreen aphid management

The rise in insecticide resistance in bluegreen aphid means extra consideration needs to be given to how this pest is managed. Regular monitoring is needed for vulnerable crops during bud formation to late flowering. 

Natural enemies can be very effective at controlling aphid populations, and ladybird beetles, parasitoid wasps, hoverflies, and lacewings are effective at suppressing Bluegreen aphids.

It is also possible to reduce damage by selecting cultivars that are more resistant to aphid feeding damage and controlling weeds around crops during summer and early autumn to remove alternate Bluegreen aphid hosts between growing seasons.

If chemical options are required (see PestNotes for the economic thresholds) avoid spraying with organophosphates & carbamates. If needed Flonicamid (MainMan) has an emergency permit approved for use on BGA in lucerne crops and sulfoxaflor (Transform) is registered for use on BGA in some pulses.

More information

AgriFutures Pasture Seeds Program Open Call: AgriFutures Pasture Seeds – Open Call for Research 2022 | AgriFutures Australia

Dr Chirgwin will give an update on the team’s research at the upcoming Lucerne Australia Field Day on Wednesday, 2 March 2022 in Keith SA. Find out more and register: https://www.lucerneaustralia.org.au/event/new-upcoming-event/

AgriFutures Pasture Seed Program, visit: www.agrifutures.com.au/rural-industries/pasture-seeds/

Acknowledgements

We would like to thank Agrifutures and Lucerne Australia for supporting this research, and the growers and advisors who have provided samples for resistance testing.  Our early insecticide baseline research on aphids, including on bluegreen aphid, has been undertaken in conjunction with CSIRO. GRDC has contributed funding for the preceding work on BGA run in conjunction with CSIRO.

Cover image: Photo by Andrew Weeks, Cesar Australia

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PestFacts south-eastern keeps growers and advisers informed about invertebrate pests and beneficials in broadacre crops and pastures during the winter-cropping season in Victoria and southern New South Wales.

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