Rethinking bluegreen aphid control as insecticide resistance spreads

When an insecticide application fails to control bluegreen aphid, application conditions may not be the only cause. Research has identified resistant populations across southern Australia, confirming that repeated reliance on broad-spectrum insecticides is no longer sustainable.

Bluegreen aphid (BGA) affects alfalfa, medic, clover and pulse crops through feeding damage and virus transmission. Populations can increase rapidly, completing a generation in around 10 days under favorable conditions.

Following the first confirmation of insecticide resistance in BGA in 2021–22, research conducted from 2022 to 2025 investigated its distribution and potential alternative controls. BGA populations were collected from pasture, pasture seed and pulse crops across South Australia, Victoria and southern New South Wales, particularly where control failures had been reported. Laboratory bioassays compared these populations with insecticide-susceptible BGA.

Resistance is widespread

The research identified another 21 populations resistant to one or more organophosphate, carbamate or synthetic pyrethroid insecticides. Resistant populations were found from the Eyre Peninsula to near Tamworth and across several parts of Victoria.

Resistance was particularly common in alfalfa but was also detected in lentil crops on the Yorke Peninsula and in Victoria’s Wimmera and Mallee regions. Resistance to organophosphates and synthetic pyrethroids was generally more common and stronger than resistance to pirimicarb.

Alternative chemistry shows promise

The project tested flupyradifurone, sulfoxaflor and flonicamid against resistant and susceptible BGA. No field-evolved resistance or cross-resistance to these active ingredients was detected, indicating that they may offer alternative control options. Registrations and permits differ between products and crops and may change.

Growers must check current Australian Pesticides and Veterinary Medicines Authority requirements and follow label directions before use.

Protecting biological control

Researchers also identified 132 parasitoid wasps collected from 25 locations across South Australia, New South Wales and Victoria. Every specimen was Aphidius ervi, suggesting that natural control of BGA may depend heavily on this species. Aphidius ervi develops inside aphids and eventually kills them.

While it is commercially available in Australia, further research is needed to determine whether targeted releases would be effective and economical in broadacre systems. In the meantime, avoiding unnecessary broad-spectrum insecticide applications can help protect existing parasitoid populations and other beneficial insects.

What growers can do now

The findings support a resistance-aware integrated pest management approach focusing on correctly identifying aphids, monitoring pest pressure, crop damage and beneficial insects, and applying insecticides only when treatment is justified.

Product selection should consider registration status, mode of action, application conditions and effects on beneficial insects. Repeated use of the same mode-of-action group should be avoided. The complete spray program also needs to be considered because applications targeting other pests can expose BGA to insecticides and increase selection pressure.

Unexpected control failures should be recorded and discussed with an agronomist or adviser. Relevant information includes the crop and field, product and rate, application date, weather and coverage, previous insecticide use and the response of the aphid population.

Resistant BGA is no longer confined to isolated fields. Avoiding unnecessary applications, rotating modes of action, protecting beneficial insects and reporting control failures will help slow resistance and retain effective control options.

Who’s behind this story?

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries.

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Andrew Zinin

Master’s in physics with research experience. Long-time science news enthusiast. Plays key role in Science X’s editorial success.

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