Stephanie Veskoukis

Bluegreen aphids (Acyrthosiphon kondoi) are a major crop pest of lucerne, lentils, lupins, medics, clover and subclover across the globe. These tiny pests can cause big problems, and the situation just got more challenging.

In a discovery during the 2021/2022 season, a collaborative project by Cesar Australia and Lucerne Australia revealed that bluegreen aphid populations in South Australia and New South Wales had evolved resistance to carbamates, organophosphates and synthetic pyrethroids.

This marked the first time resistant bluegreen aphid populations had been confirmed anywhere in the world.

Context: A Community Effort

The first signs of resistance emerged in 2018, when growers and agronomists based around the limestone coast of South Australia in the lucerne seed industry suspected that something was amiss. Their pest control efforts weren't yielding the usual results.

It was the industry itself that spearheaded the quest for answers. Dr Katrina Copping, Executive Officer of Lucerne Australia recounted the response to these early warning signs, and the subsequent demand for research, “The push was from industry… growers were reporting control failures. One of the [consultants] had sent off samples to [Cesar], and there was some initial screening done that suggested that there was a problem.”

Copping highlighted the proactive steps taken, saying “Industry came to Lucerne Australia to say, ‘we think there’s a problem, we need to get to the bottom of this.’, so then we actively pursued research funding through AgriFutures Australia… and Cesar was the successful organisation for that tender.”

A Key Turning Point

When Cesar Australia confirmed that bluegreen aphids had evolved resistance, it marked a key turning moment for the Keith region, “it allowed industry to understand that it wasn’t a control failure due to how they’d applied it, or the rates they were using, or the conditions they were putting it on under, or the choice of product, it was actually a resistance issue.” remarked Copping.

“There’s definitely a much greater awareness of the fact that the products that they’ve relied on for a long time don’t work as well as they used to, or don’t work at all… there’s definitely been changes in the industry,” Copping said.

Rising to the challenge

Scott Hutchings, key agronomist for the region and Lucerne Australia Chairperson shared how a shift towards implementing integrated pest management (IPM) strategies has helped industry rise to the challenge of working with limited chemical input options.

Central to IPM is the principal strategy of being more selective about the timing and toxicity of chemical control applications. Hutchings has successfully helped his clients adopt this approach, emphasizing the importance of precision and restraint.

When Hutchings encounters a bluegreen aphid population in a client’s crop, his first strategy is to ‘Hold the spray’: “our first approach is to really not spray them unless we have to, you know, we’re trying to let the beneficials build up.”

By adopting a chemically conservative control strategy, farmers are boosting the first line of defence in an Integrated Pest Management (IPM) system: beneficial and predatory insects that naturally keep pest populations in check.

This shift marks progress in pest management practices, yet challenges remain. One major hurdle is the persistent difficulty in getting new active ingredients registered.

Copping described the lack of registered chemical control options as a limiting factor in the industry’s ability to apply best practice management approaches, “We’re only a minor industry, and access to some of the newer generation insecticides is definitely a challenge, because we’re only a small industry, we have to go down the avenue of seeking access to minor use permits.”

Given the limited chemical control options at the industry’s disposal, Copping proposed IPM as the way forward for the industry, “They do need to move to a uniform IPM program going forward, and I think the industry is well aware of that.”

Integrated Pest Management

Scott Hutchings echoed this sentiment, pointing to second generation grower and seasoned lucerne seed producer Scott Campbell as an example of innovation with successful results.

Lucerne has been a core component of Campbell’s business for over 40 years, and he hasn’t gotten this far by controlling pests like bluegreen aphids with the same two chemicals year on year.

Reflecting on his enduring success in the industry, Campbell said, “At the end of the day once they’re in the crop, that’s really the only strategy that we’ve got, it’s just integrated pest management.”

For Campbell, keeping an eye on beneficial insects is a cornerstone of his Integrated Pest Management (IPM) strategy. “We’re looking at beneficials numbers and trying maintain beneficials as much as we can… we’re trying to create a balanced system, we don’t want to wipe everything out – that’s how we create more issues.”

Campbell and Hutchinson have been successfully monitoring beneficial insects in their lucerne seed crops for a few years now, utilising Campbell’s mixed farming enterprise structure to their advantage: “… if we do get infestations prior to lock up of seed and they’re not for hay, we’re just grazing them off.” Hutchinson said.

The lucerne seed industry has been incorporating elements of Integrated Pest Management (IPM) since the mid-1980s. However, a crucial aspect of IPM—rotating effective selective chemicals in spray programs—has hit a significant roadblock. The scarcity of currently effective selective chemistry for combating bluegreen aphids is hindering widespread IPM adoption in the region.

Copping points out, “We don’t actually have a lot of options at present… if [new actives] could be registered, it would allow industry to have a wider range of chemical options that they can then integrate into their programs.”,

Scott Hutchings echoes this sentiment, adding, “We haven’t had any significant chemistries to rotate to for a number of decades.”

Takeaways

As agronomists and scientists trial new chemicals and explore predatory insects to combat bluegreen aphids, Scott Hutchings remains concerned about the limited options for chemical rotation, “The pest is evolving quicker than we can bring the tools to market,” he warns, highlighting the increasing selection pressure for further resistance evolution.

As new beneficial insect research continues to come to light, the lucerne seed industry is quite aware that it’s in their best interests to practice integrated pest management and preserve the efficacy of the currently available chemistries for as long as possible. Campbell earnestly expressed of himself and his peers, “We just want the industry to be sustainable long-term.”

The bluegreen aphid’s resistance evolution and the lack of chemical control options registered and on the market is a stark reminder to the broader grains industry of the dangers of relying too heavily on a few modes of action for pest control. This scenario highlights the critical need for diverse strategies to combat pests effectively.

Industry leaders in the region of Keith like Scott Campbell are eagerly anticipating new additions to their IPM toolkit - including the development and registration of selective chemistries, the identification of bluegreen aphid predators, and the development of aphid resistant lucerne varieties.

One thing is abundantly clear: innovation and adaptation are essential for thriving in the face of agricultural challenges. From the efforts of farmers like Scott Campbell to the collaborative research initiatives led by industry experts, the lucerne seed industry is paving the way with determination and resilience.

Acknowledgements

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.

The current bluegreen aphid insecticide resistance research is being funded by AgriFutures Australia and the GRDC. Cesar Australia are conducting this research in collaboration with Lucerne Australia. We thank all the growers and agronomists who assisted with sample collections and chemical history information, Katrina Copping and Scott Hutchinson of Lucerne Australia, and Scott Campbell, seasoned lucerne seed grower, for their contributions to this case study. We would also like to thank Dr Evatt Chirgwin, who leads the bluegreen aphid research projects.