Introduction To Bluegreen Aphid Control
The bluegreen aphid (BGA) is a significant pest that affects various crops, including alfalfa, medic, clover, and pulse crops, through feeding damage and virus transmission. Populations of BGA can increase rapidly, completing a generation in around 10 days under favorable conditions. In recent years, the repeated use of broad-spectrum insecticides has led to the development of resistant populations, making it essential to rethink bluegreen aphid control strategies.
Understanding Insecticide Resistance
Research conducted from 2022 to 2025 investigated the distribution and potential alternative controls of BGA in southern Australia. The study found that resistant populations are widespread, with 21 populations resistant to one or more organophosphate, carbamate, or synthetic pyrethroid insecticides. 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. The findings suggest that the repeated reliance on broad-spectrum insecticides is no longer sustainable, and alternative control methods are necessary.
Alternative Control Options
The project tested alternative insecticides, including flupyradifurone, sulfoxaflor, and flonicamid, against resistant and susceptible BGA populations. The results showed that these active ingredients may offer alternative control options, as no field-evolved resistance or cross-resistance was detected. However, growers must check current Australian Pesticides and Veterinary Medicines Authority requirements and follow label directions before use. Additionally, researchers identified 132 parasitoid wasps, which are natural predators of BGA, suggesting that protecting biological control methods is crucial.
Protecting Biological Control
The study found that every parasitoid wasp specimen collected was Aphidius ervi, which develops inside aphids and eventually kills them. While Aphidius ervi 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. This approach can help maintain a balanced ecosystem and reduce the risk of insecticide resistance.
Integrated Pest Management
The findings support a resistance-aware integrated pest management approach, focusing on correctly identifying aphids, monitoring pest pressure, crop damage, and beneficial insects. Growers should apply insecticides only when treatment is justified and consider the registration status, mode of action, application conditions, and effects on beneficial insects. Repeated use of the same mode-of-action group should be avoided, and the complete spray program should be considered to minimize the risk of insecticide resistance. By adopting this approach, growers can reduce the risk of control failures and protect their crops from BGA infestations.
Sources
This is an original synthesis by Qivorane based on reporting from the outlets below.
