CitrusWatch: A new industry biosecurity program

Author: Dr Jessica Lye

Biosecurity helps us understand what the risks are to our primary production and provides a systematic, risk-based method of protecting these assets. It supports the health of ecosystems, reduces the need for pest management, and keeps our food supply chains reliable and resilient. While it may not be the most exhilarating conversation starter, it is one that needs regular air-time in our industry to minimise the risk of exotic pests. In this article we share an overview of CitrusWatch, a new industry biosecurity program that will help to keep this conversation going and help protect industry, businesses and regional communities into the future.

Thanks to our biosecurity system, and our geographic isolation the Australian citrus industry is free from many harmful citrus pest species, affecting other countries. We know from other countries’ experience that huánglóngbìng (HLB), also called citrus greening, has devastating effects on citrus production. After huánglóngbìng was detected in Florida in 2005, production decreased by 74 per cent.

In the 2003-04 season, before HLB was discovered in the state, Florida produced 242 million boxes of oranges and 40.9 million boxes of grapefruit. In 2020-21 production declined to 52.8 million boxes with a University of Florida economist recently predicting further reduction over the next decade at the current rate of tree replacement. In real terms, this means growers have gone out of business, and millions of dollars have been put into management systems to keep businesses viable.

In recognition of biosecurity threats such as huánglóngbìng, and building on previous biosecurity projects, a new five-year biosecurity program, ‘CitrusWatch’ has been launched. This program is funded by Hort Innovation through the citrus R&D levy and funding is also supplied by Plant Health Australia (PHA) using the citrus plant health levy. The program is led by PHA, with Citrus Australia coordinating program activities. The Northern Territory Department of Industry Tourism (NT DITT) and trade and research group Cesar Australia, will provide surveillance, communication and research support.

CitrusWatch will be a collaborative, national program that will extend its reach from commercial production zones, to high-density, high-risk, high traffic urban and peri-urban regions, to support an early detector network both within the industry and throughout the general public more broadly. It will link with biosecurity agencies, biosecurity programs in other industries, and research and extension programs. Ultimately, the program will aim to ensure that the Australian citrus industry is better equipped to minimise the entry and spread of high priority pests, such as Asian citrus psyllid (Diaphorina citri), African citrus psyllid (Trioza erytreae) and diseases such as huánglóngbìng. The industry will retain access to key markets by collecting robust surveillance data, having surveillance mechanisms and expertise in place to quickly detect, identify, and address incursions of citrus high priority pests.

A breakdown of the program is included below.

Expanding our surveillance

Instances of early exotic pest detection have frequently demonstrated the benefits of early action during an incursion, and the example of citrus canker detection and subsequent eradication in the Northern Territory is a very recent reminder for the citrus industry.

Thanks to efforts from previous biosecurity coordinator, Jeff Milne, and many other contributors, 2018 – 2021 saw an exotic pest sticky trap network take shape that established the start of a network for early detection of some of the citrus industries high priority pest threats.

Through Citrus Watch, this early detector network will continue and expand. The program aims to deploy 1000 sticky traps each year across urban residential areas and commercial citrus orchards to aid in early detection of Asian citrus psyllid, as well as other high priority threats, such as African citrus psyllid and glassy winged sharpshooter (Homolodisca vitripennis), vector of the pathogen Xylella fastidiosa. While early pest detection is the major goal of the program, these surveillance activities have the added benefit of increasing communication and awareness and adding to an industry dataset that can provide ‘evidence of absence’, since we are collecting valuable data, such as location, trapping dates, and host plants.

Once traps are collected from the field in spring and autumn, they are sent to diagnosticians for initial screening. Suspected exotics are sent to the relevant state biosecurity agency for further diagnostics. The early detector sticky trapping network is coordinated between the NT DITT and Citrus Australia, with the former focussing on Northern Australia and the latter focussing on southern Australia. We are currently in the midst of spring trapping. Over 300 sticky traps have been mailed to early detectors throughout southern Australia and of these, approximately 150 have already deployed in the field (in urban and commercial growing areas). Collected traps are beginning to find their way to experts for screening.

Surveillance in urban areas

Large port-based urban areas are high-risk potential entry points for exotic pests such as Asian citrus psyllid. The good news is there are many eyes and a lot of goodwill in these areas that can help us with early detection. During the program, sticky trap surveillance in high density urban areas, particularly those near major ports of entry, will be a focus. This spring we will start targeted surveillance for exotic psyllids in the Greater Melbourne region. Collection of bud stick samples through CitrusWatch will also occur, with these samples tested for huánglóngbìng through the project “Improving diagnostics and biosecurity for graft-transmissible diseases in citrus (CT17007)”, led by Dr Nerida Donovan at the NSW Department of Primary Industries.

Industry training

The CitrusWatch program also has an industry training component. As the program progresses, we will collect information on what our industry needs, which will serve as a basis for developing training packages and information resources specific to industry needs.

Resources include information materials designed to increase the level of familiarity with high priority, high impact exotic citrus pest species. The more growers, crop scouts, packhouses and nursery managers aware of exotic species and how to recognise them, the higher chance of finding an exotic pest in the early stages of an incursion, when pest population levels are low and contained to a specific area. This early detection scenario  significantly improves the likelihood of achieving an eradication.

Face-to-face workshops on pest surveillance and identification will also be organised, where domestic pest and disease experts will share their knowledge. To connect with international expertise on exotic pest species, the program will organise and host two study tours for interested industry members.

Risk assessment and modelling

The industry biosecurity plan (Biosecurity Plan for the Citrus Industry – Version 3; PHA, 2015), which can be found on the biosecurity page of the Citrus Australia website, underpins biosecurity preparedness. Resources and funding can only stretch so far, and the biosecurity plan provides a valuable basis for planning priority preparedness activities for the industry (such as our sticky trap network). Importantly, the plan includes a detailed risk assessment that considers the risk of exotic pest entry into Australia, the risk of a population establishing, the risk of spread throughout growing regions, and the economic impact to the industry.

Due to the work involved, development of industry biosecurity plans is a significant undertaking. The biosecurity plan is due for review, therefore it will be included as an early activity in the program. Another activity will be modelling the Asian citrus psyllid risk of entry, spread and establishment based on available biological and climatic data. Modelled predictions will be important in helping us design future surveys based on the highest risk of location and timing of pest entry and spread.

Governance and collaboration

The Citrus Pest and Disease Prevention Committee, and a representative from Hort Innovation, is acting as the Steering Group for CitrusWatch and will play a key role in the direction of activities in the program over the next five years. CitrusWatch will also strongly collaborate with the recently launched Australian Centre for International Agricultural Research/Hort Innovation project ’Preparedness and management of huánglóngbìng (Citrus greening disease) to safeguard the future of citrus industry in Australia, China and Indonesia’. This project is being led by Dr Jianhua Mo from New South Wales Department of Primary Industries and involves multiple international and domestic collaborators. Several activities in this project will have direct benefits for Australian citrus growers, such as testing of Asian citrus psyllid attractants and trap types overseas, and a training campaign on huánglóngbìng preparedness.

Keep an eye out for further details about upcoming training opportunities offered through the program as well as an update on sticky trap and targeted surveillance activities in later issues. If you wish to get involved in CitrusWatch as a sticky trap program participant please get in touch with Jessica Lye at Citrus Australia at Jessica.lye@citrusaustralia.com.au

CitrusWatch is a collaborative, national program that aims to protect the Australian citrus industry from harmful exotic pests. CitrusWatch has been funded by Hort Innovation, using the citrus research and development levy and contributions from the Australian Government. Hort Innovation is the grower owned, not-for-profit research and development corporation for Australian horticulture. Funding is also supplied by Plant Health Australia using the citrus plant health levy. Project partners are Plant Health Australia, Citrus Australia, the Northern Territory Department of Industry Tourism and Trade and Cesar Australia.”

References

Citrus Industry Magazine, accessed 13 October 2021. Florida Production Faces Further Decline

https://citrusindustry.net/2021/08/11/florida-production-faces-further-decline/

Plant Health Australia (2015) Biosecurity Plan for the Citrus Industry – Version 3

Singerman, A. and Rogers, M. (2020) The Economic Challenges of Dealing with Citrus Greening: The Case of Florida, Journal of Integrated Pest Management, Volume 11, Issue 1, 3, https://doi.org/10.1093/jipm/pmz037