Investing in pest and disease management is paramount in ensuring the sustainability and productivity of the macadamia industry. Like other sectors, the industry faces persistent challenges, including reduced yields and compromised nut quality. Therefore, proactive management strategies are essential and research and development to address these threats is a top priority for Hort Innovation.

A case study in disease management

The improved productivity and profitability of Australian macadamia growers was front of mind during the delivery of the recently-completed project Macadamia integrated disease management (MC16018). In collaboration with the University of Queensland this project built on earlier efforts to improve training and communication initiatives, as well as diagnostic capabilities for a range of priority diseases for the industry, including husk spot, Phomopsis husk rot, flower bright complex, Phytophthora root rot, and branch dieback.

Steve McLean, a grower and consultant based in the Northern Rivers, NSW, with more than 30 years of experience in the macadamia industry, played a key role in this project. Steve contributed as the chair of the project steering committee and a member of Hort Innovation’s Strategic Investment Advisory Panel (SIAP) and participated directly in field trials with other growers.

Reflecting on the significance of the project, Steve emphasised the crucial role of continuous research in managing macadamia diseases. “Disease can have a huge impact on macadamia production. If there is a major outbreak, you can lose 20-30 per cent of the crop, possibly more,” he explained. “This research helps us stay ahead of the curve by providing practical solutions and steadily improving management practices.”

The project uncovered new information about the biology a nd ecology of endemic and emerging diseases in macadamia. It found that macadamia diseases are complex and result from multiple pathogens.

For example, the project identified 12 known plant pathogenic species and 14 new pathogens, which were proven to cause diseases in macadamia for the first time. This research also led to significant improvements in diagnostic capabilities, allowing for better identification and management of these diseases. The impact of the environment on disease severity contributed to decreased productivity.

One of the project’s most significant outcomes for growers was the registration of new fungicides for controlling flower blight and husk spot. “Getting these fungicides registered was a big win for the industry,” Steve noted. “It gives growers another tool in the fight against these diseases and it helps reduce the risk of resistance developing in the long term.”

Beyond introducing new chemical options, the project also led to advancements in cultural practices. For instance, the research identified that stick tights — unharvested nuts that remain attached to the tree — are a major source of husk spot infection.

By shaking the trees to remove these stick tights, growers can significantly reduce the risk of husk spot in the following season. This simple practice has been adopted across the industry, leading to better disease control and reduced management costs.

“The identification of stick tights as a major infection source for husk spot was a game-changer,” Steve remarked. “It is another example of how this research does not just sit in a lab; it is directly applied in the orchard to improve outcomes.”

Communication and adoption were also critical components of the project’s success. “The whole industry has benefited from the program,” Steve said. “It is not just about doing good research, but also making sure that the findings are getting out to the people who need them — growers, consultants, everyone involved in the industry. This has been a key factor in the success of the project.”

Steve also emphasised how the program complemented other research projects, such as pest management and industry benchmarking, tracking the impact of practice change due to the projects. By understanding the interactions between pests and diseases, the industry has made more informed decisions, leading to steady improvements in orchard productivity and disease management practices.

Looking forward: New investments in pest and disease management

New projects An integrated systems based approach for pest management in Australian macadamia (MC21000), and An integrated disease management approach for the Australian macadamia industry (MC21001), are designed to build upon the foundation laid by previous initiatives, leveraging the latest advancements and insights to further fortify the industry’s defence against pests and diseases.

Project MC21000 is establishing a decision-support system to facilitate timely and effective pest management decisions for Australian macadamia growers and other industry stakeholders. Building off previous work that established a knowledge database of key pests, biocontrol agents and pest management priorities in macadamia orchards, this project is developing a comprehensive, integrated management package. The package will incorporate ecological and environmental dimensions and fit into the regional/local macadamia orchards ecosystem. The system will enable growers to make informed choices based on the latest research and best practices; by building on previous research and developing new pest monitoring protocols, this initiative aims to improve the overall resilience and productivity of the macadamia industry.

One of the most exciting aspects of MC21000 is its focus on biological control. The project is conducting regional and field studies to identify natural enemies of key macadamia pests. By understanding the seasonal abundance and diversity of these natural enemies, the project aims to improve the sustainability of pest management practices in the industry.

Project MC21001 focuses on deepening the understanding of macadamia diseases, including disease ecology and the broader environmental factors that influence disease pressure. This project is generating new knowledge and innovative tools to predict, monitor and control diseases in macadamia orchards.

By training future researchers and providing direct support to growers, this project aims to equip industry with tools to underpin future prosperity. Through scientific studies, innovative tools and national research and extension activities, this project aims to deliver significant long-term benefits, including increased harvest yields, reduced costs and minimised environmental impacts. By disseminating integrated disease management information, the project ensures growers have the best possible resources at their disposal.

As the macadamia industry continues to grow and evolve, pest and disease management challenges will remain a central concern. Through strategic investments in research and development, Hort Innovation is equipping the macadamia industry to meet these challenges head-on.