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Ongoing project

Macadamia integrated disease management (MC16018)

Key research provider: The University of Queensland

What’s it all about?

Beginning in late 2017, this project is tasked with delivering a holistic integrated disease management program – which is compatible with integrated pest management – to increase the productivity and profitability of macadamia growers and the Australian macadamia industry at large.

Its work includes a combination of research, training and communication activities, to improve management approaches and diagnostic capabilities for a range of priority diseases for the industry, including husk spot, Phomopsis husk rot, flower bight complex, Phytophthora root rot, and branch dieback.

Since May 2020, the team have tested fresh field and stored isolates of husk spot fungus Pseudocercospora macadamiae for sensitivity to pyraclostrobin and carbendazim fungicides. The results showed that the fungicides were effective and reduced mycelial growth in both the field and stored isolates. All the isolates maintained their sensitivity to both fungicides at the same levels as previous doses used in 2013.

The team also assessed varietal susceptibility to Diaporthe australiana in vitro. Significant differences were observed among five macadamia cultivars.

Due to COVID-19 travel restrictions, planned project extension and adoption with growers and crop consultants has been limited. However, access to diagnostic and disease management information was provided via phone calls with crop consultants when requested.


Read more about the Leaf diseases in macadamia, published in the Australian Macadamia Society News Bulletin on pages 62-64 of the Spring 2020 edition

Learn more about macadamia integrated disease management in a dedicated section published by the team on pages 18-21 of the Macadamia Plant Protection Guide 2020-21, from the NSW Department of Primary Industries.

Phytophthora root and stem canker cause significant economic losses in macadamia. In the past year the project team have worked to develop diagnostic tools and treatment practices for better disease control. 

As part of this work, the team developed a new in vivo macadamia whole-leaf dip assay which proved to be simple and effective compared with existing assays. This new tool will assist with screening macadamia germplasm and breeding programs for susceptibility to various Phytophthora species.

Phosphonates have been successfully used to control Phytophthora root rot and stem canker in macadamia, however there are concerns that phosphite residue may accumulate in the kernel if application is made during the kernel maturation stage. The team tested the sensitivity of macadamia flowers to foliar and bark spray applications, with the results showing no detrimental effect on macadamia flowers and nut set after the spray application of phosphonates at flowering and various tree phenological stages.

Due to Covid-19 travel restrictions, field sample collection related activities were delayed.

Research to analyse the sensitivity of Phytophthora to phosphonates in macadamia roots could not be completed as field sample collection was disrupted due to Covid-19 travel restrictions. Fresh samples will be collected and analysed during the 2020/21 production season.

At the February 2020 Australian Macadamia Society MacGroups, growers were updated on the latest regional major disease trends and provided a demonstration of field diagnostic tools to differentiate Botryosphaeria branch dieback from general drought conditions on mature trees.


Read more about the project in this article, Resilience of macadamia trees to diseases, published in the Australian Macadamia Society News Bulletin, 2020 Winter edition.

The researchers have continued their research, extension and diagnostic activities, specifically…


Field trials are being set up to investigate the effectiveness of eight fungicides against various pathogens causing diseases in macadamia, including husk spot, husk rot and flower blights.

Field trials are also underway to examine the effectiveness of cultural practices such as the influence of insect pest management on husk rot incidence.


The team contributed to over ten face-to-face industry meetings including MacGroups, crop consultant meetings, workshops and trainings, providing many opportunities for growers to learn about, and contribute to, project activities.

new guide to macadamia diseases was developed for these workshops, which growers can use to pinpoint problems in their orchards.

Diagnostic services

35 samples were received from growers, consultants and macadamia nurseries for identification with results and advice allowing growers to make decisions about management in their orchard.


Through the project team’s consultation with industry and other R&D initiatives, research activities within the project have now been planned and will include…

  • Building a better understanding of the biology and spread of priority diseases

  • Looking at disease resistance, including investigating varietal susceptibility and developing tests for screening germplasm for resistance traits

  • Diagnostic and surveillance work, including developing and assessing diagnostic protocols and working towards early detection and characterisation of new and emerging pathogens

  • Crop protection activities including screening and looking at the efficacy of crop protection products, developing use patterns for them and developing disease management strategies.

At the time of writing, work to assess the efficacy of select fungicide products was underway. In December 2017, two field trials were established in commercial macadamia orchards in Bundaberg to examine the effectiveness of three products on the incidence of Phomopsis husk rot, with effects on yield currently being assessed. Data collection on the effect of the treatments on yield are currently underway. Arrangements are also in place for further Phomopsis work, plus efficacy field trials for flower blight that will take place in the Northern Rivers, Sunshine Coast and Gympie.

Investigations on the factors and conditions that influence disease outbreaks are also underway. This information will underpin disease management strategies developed by the project. The project team report that recent research activities on Phomopsis husk rot have improved knowledge of the causal agent, including revealing that the disease is caused by two new species within the fungal pathogen Diaporthe genus, which are unique to macadamia. They add that there are significant variations in varietal susceptibility, which the researchers will explore with the industry’s breeding program (MC14000).

In working towards its goals, the project will also be developing the next generation of researchers for the industry. The University of Queensland has awarded scholarships for two PhD students to work on the project, with their work focused on flower blight (the pathogen biology, disease epidemiology and host-pathogen interaction) and the ecology and host-pathogen interaction of Phytophthora in macadamia.


The project has produced the below fact sheets for identifying diseases…


Related levy funds

This project is a strategic levy investment in the Hort Innovation Macadamia Fund