Hundreds of delegates from all over the world recently gathered in Sydney for the most important event in the fruit fly research calendar, the 11^th International Symposium for Fruit Flies of Economic Importance.

The National Fruit Fly Council’s Stuart Burgess and Chris O’Connor attended the symposium to join discussions on strategies to manage the impact of fruit flies into the future.

Covering all relevant disciplines ranging from basic knowledge to applied research to program implementation, the following sessions were presented in a hybrid format:

1. Biology, Ecology, Physiology and Behaviour
2. Taxonomy and Morphology
3. Genetics and Biotechnology
4. Chemical Ecology and Attractants
5. Risk Assessment, Quarantine and Post-harvest
6. Sterile Insect Technique
7. Natural Enemies and Biological Control
8. Other Control Methods
9. Area-wide Integrated Pest Management and Action Programs
10. Social, Economic and Policy Issues of Action Programs

We share a few highlights of the symposium.

Opening ceremony

In his welcome address, Polychronis Rempoulakis, a member of the International Steering and Organising Committee, said the first Symposium was held in Athens, Greece, 40 years ago, with 22 countries, three international organisations and 115 participants.

Convened every four years, the last symposium was held in Mexico in 2018 and it was announced that the next event will take place in Morocco in 2026.

Rui Cardosa Pereira, Chair of the International Steering and Organising Committee, highlighted the need to find out what is happening in RD&E and the impact on trade, and that the use of more environmentally friendly techniques to manage fruit flies are crucial to our future.

As part of the opening ceremony, Dr Bertie Hennecke, Assistant Secretary for Plant Health Policy at the Australian Chief Plant Protection Office within the Department of Agriculture, Fisheries and Forestry (DAFF), discussed the Australian perspective to managing fruit flies of economic importance.

He said Australia’s biosecurity system is under increased pressure, facing multiple threats on multiple fronts.

“The Commonwealth deals with 2.5 million shipping containers, 90,000 flights, 19,000 ships and 144 million parcels, all of which offer potential pathways for incursion,” he said.

According to Dr Hennecke, the horticulture industry in Australia has the highest growth potential and fruit flies cost the industry more than $300 million annually. Some of the challenges to growing the industry include managing endemic and established fruit fly species, building preparedness and agility, continuing to grow exports, establishing sustainable funding arrangements and strengthening the national management system.

Director of Plant Biosecurity and Product Integrity, New South Wales Department of Primary Industries, Satendra Kumar posed the first question of the day: How do we actually prepare?

He said there are numerous pathways of entry in Australia, which makes it a large and complex environment.

Opening keynote

Professor Ary Hoffman, Laureate Professor from the University of Melbourne, delivered the keynote address, discussing fly evolutionary adaptation: what have we learnt, where are we going? He outlined his journey from basic population comparisons for Drosophila through to modern day genomics.

According to Prof Hoffman, by incorporating evolutionary adaptation in species, distribution modelling reduces projected vulnerability to climate change.

“Studies have shown evolution has a large impact on predicted distributions, as in Northern Australia showing current, predicted and evolutionary changed genetics for the future distribution for certain species,” he said.

“Incorporating evolutionary adaptation in species distribution modelling, reduces projected vulnerability to climate change.”

Fundamentally, this work is key to leading to predictions about species in changing climates.

Mitochondrial genetic diversity of Bactrocera dorsalis captured in California over a 14-year period

Dr Norman Barr, a Research Scientist at the United States Department of Agriculture, conducts research on the molecular systematics and diagnosis of plant pests, and he serves on the FAO/International Plant Protection Convention’s (IPPC) Technical Panel for Diagnostic Protocols to support adoption of internationally harmonized protocols for global pests.

In his presentation about Mitochondrial genetic diversity of Bactrocera dorsalis (Oriental fruit fly) captured in California over a 14-year period, Dr Barr outlined the sequencing of Cytochrome c oxidase subunit 1 (COI) from flies trapped in California, to evaluate the Hawaiian source hypothesis of each fly.

His presentation referred to records captured over a 14-year period (2008-2021) using single nucleotide polymorphism (SNP) typing protocols to test if the Hawaii exclusion test is supported by the fly nuclear genome.

Research showed that the genetic diversity of Bactrocera dorsalis captured in California over the 14-year period is relatively high, ultimately providing further evidence for multiple invasions of Oriental fruit fly into California. Over half the flies found in California were sourced from regions other than Hawaii.

Rapid screening of tephritid surveillance traps using DNA metabarcoding

Alexander Piper, Researcher at Agriculture Victoria and the School of Applied Systems Biology, at La Trobe University, presented on the rapid screening of tephritid surveillance traps using DNA metabarcoding. DNA metabarcoding presents an alternative high-throughput sequencing (HTS) approach for multi-species identification.

The research was undertaken in Australia through a collaboration between Agriculture Victoria, the Queensland Department of Agriculture and the New South Wales Department of Primary Industries.

Research focussed on further developing high throughput taxonomic screening of tephritid surveillance trapping which is aimed at reducing the technical and financial impost in surveillance. The work allows for a non-destructive analysis of populations with the ability to also undertake the traditional morphological approaches where required.

It can be used in Area Wide Management (AWM) for better understanding of the populations of fruit flies in a region and then more targeted management approaches.

Identifying translocation breakpoints in tephritid genomes     

Dr Sheina Sim, Research Entomologist at the United States Department of Agriculture, presented on identifying translocation breakpoints in tephritid genomes.

Her research focusses on Zeugodacus curcurbitae (Melon fly) and translocation.

Dr Sim’s work relates to Genetic Sexing Strains (GSS) used in non-transgenic Sterile Insect Technique (SIT) colonies for sex sorting and male-only releases such as that being developed here in Australia through our SIT program.

She said the CRISPR-based methods are aimed at greater accuracy (fewer ‘off-target effects’) and increased speed and therefore increased efficiencies.

“Near gapless genome assembly for melon fly can assist with diagnostic and SIT work in the future,” she said.

New generation of genetic sexing strains facilitate colony refreshment for SIT applications: proof-of-principle in medfly

Dr Carlos Caceres, Research Entomologist and Head of the Plant Pest Group at the joint FAO/IAEA Centre for Nuclear Techniques in Food and Agriculture, presented his work relating to the management of lab populations of fruit flies for Sterile Insect Technique (SIT), with particular relevance to Ceratitis capitata (Medfly).

More specifically, his research relates to a new generation genetic sexing strains (GSS) system and the refreshment of the SIT source colonies with wild populations.

The goal of this work is to increase genetic variability, potentially improving sexual performance, in turn improving SIT effectiveness and efficiencies.

“This has enabled the introduction of fresh genetic material into mass-reared colonies (SIT), potentially improving both the quality of mass-produced males and efficiency of medfly SIT action programs,” he said.

Global population genomics of Oriental fruit flies using RAD-seq

Dr Michael San Jose, Researcher at the University of Hawaii’s Department of Plant and Environmental Protection Sciences, uses modern approaches in systematics, population genetics, and genomics to understand the evolution of Tephridae. His current research focuses on Bactrocera dorsalis (Oriental fruit fly) and other closely related species.

His presentation focussed on the diagnostic work for surveillance of detected Oriental fruit fly. He said prior population genetics techniques haven’t been adequately resolved for surveillance activities.

The techniques used for this research were restricted enzyme associated DNA sequencing (RAD-seq). It was shown to be successful in detecting structures in this species that were not found using less data-rich methods. The work further enhances the ability to use this method for source estimation studies of the pest and can be used across other regional location populations that are detected.

Development of novel SIT methods for disrupting populations

Dr Atsushi Honma, Researcher at the Okinawa Prefectural Plant Protection Centre, is currently working on biology and genetics of Bactrocera dorsalis (Oriental fruit fly) complex and the development of novel SIT combined with reproductive interference.

Bactrocera dorsalis invaded the southern and southwest island in Japan but were initially eradicated using MAT and SIT in 1986. The Okinawa Prefecture was the main region where this occurred. Incursions of Oriental fruit fly have occurred every year since 1986 and have been increasing in recent years, particularly during COVID-19. Pathways include wind-driven dispersal from southern China as well as accidental importation from the Philippines and Taiwan.

“Possible immigration sources have been mapped using a backward trajectory analysis with 65.8% of flies identified as wind-borne,” Dr Atsushi said.

He said understanding the method of arrival is key to enable effective counter measures and accompanying surveillance approaches to manage the risk of future incursions.

“Drastic changes to incursions occurred in 2021, with a majority coming from non-Philippine sources, which is significantly different to previous years. This data provides much-needed information to enhance Okinawa’s capacity to reduce the risk of future incursions of Oriental fruit fly,” Dr Honma said.

It was noted that Oriental fruit fly SIT males will continue to be deployed into the future.

For more information, visit the ISFFEI website.