Integrated disease management of black core rot in citrus (CT20008)

Ongoing project

Delivery Partner: The University of Queensland

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What is it all about?

This investment is developing integrated pest and disease management (IPDM) tools for the effective management of citrus black core rot. Black core rot (Alternaria spp.) is a significant and emerging issue in southern citrus growing areas; the internal rot and bitter flavours of infected fruit are often undetected until they reach the kitchen bench or the juicing plant.

Increased understanding of the disease, its lifecycle and underlying epidemiological factors will help to identify potential management options for citrus black core rot, which can be tested and validate prior to their inclusion into the current citrus IPDM program.

In the initial stages of the project, the research team will be:

Establishing the occurrence and impact of black core rot in citrus through field surveys, interviews with growers and others involved in the citrus supply chain
Identifying the Alternaria species causing black core rot
Identifying sources of inoculum and timing of infections through targeted field trials
Establishing the effectiveness and limitations of current practices that are used
Addressing the gaps in knowledge of the disease cycle and pathogen biology of citrus black core rot and investigating the underlying biological factors affecting disease control.

After these investigations have taken place, the research team will:

Leverage the improved understanding of the epidemiology and disease cycle to test new disease management options involving integration of existing and new chemical, cultural and biological tools to reduce the impact of black core rot in citrus.
Explore choices and timings of chemical and other control options for citrus black core rot that can be integrated into an IPDM program.
Collaborate with existing and past projects, national and international networks to gather, communicate and extend new knowledge and practices from the project that will maximise adoption and commercial benefit across the citrus industry.

Throughout the project, a young post graduate student will be trained in all aspects of field pathology to increase the future research capability of the Australian citrus industry.

Project update: June 2023

Alternaria isolates from several orchards in New South Wales (NSW) have been identified. An additional 68 historical isolates from NSW and Queensland (QLD) herbariums have been identified and fungal isolates from leaves and fruit infected with Alternaria brown spot have been collected from QLD to allow for later identity comparisons between geographically separate orchards.

Furthermore, current control strategies for Alternaria black core rot have been surveyed across three Australian states and existing control options have been short-listed for future evaluation. Several control strategies were identified, however, there is insufficient evidence to provide support with a high level of confidence on any of these currently employed strategies.

Epidemiological trials are underway with a 2022-2023 field trial in Griffith, NSW, to determine the timing of infection of the black core rot pathogen in imperial mandarins as well as the source of inoculum in orchards. Additional epidemiological trials are planned for 2023 and will enable the project team to characterise the pathogen’s sporulation patterns and infection processes.

Finally, engagement with industry regarding the progress and our learnings remain a directive force and motivator behind this project. NSW DPI has presented the project and its initial understandings to Western Australian citrus growers and a section on citrus health in general was co-authored by UQ and published by the International Society for Plant Pathology.

Project update: November 2022

Over the past six months, the research team report progress in the following:

A grower survey was conducted to determine occurrence, impact, and effectiveness of black core rot control.
A collection of Alternaria strains causing disease in citrus has been established. Several surveys in the Riverina in June-July 2022 resulted in the collection of 43 Alternaria isolates from various citrus orchards and the research team has documented an additional 70 historical Alternaria isolates available at state-based Herbariums.
A field trial has been established on a grower’s property near Griffith aimed at determining the source of inoculum and the timing of infection of Alternaria.