While many Australian producers are familiar with the challenges posed by Queensland fruit fly or Mediterranean fruit fly, there are other exotic fruit fly species that pose a similar threat to horticultural production, and they’re already on our doorstep.
Darryl Barbour, Manager of the National Fruit Fly Council, who works at Plant Health Australia (PHA), explains the threat and how it is tackled in the Torres Strait by an arrangement agreed between governments and industry bodies.
The Australian mainland is separated from Papua New Guinea, and various exotic species of fruit flies, by only a 150km stretch of ocean—the Torres Strait—which is dotted with over 200 islands that provide stepping stones.
Every year, strong seasonal winds bring exotic fruit flies from the north onto some of these islands. If left unmanaged, fruit flies could establish on one island before making their way progressively further south to eventually reach the Australian mainland. Here they would wreak havoc through Australian horticulture, posing a huge problem for producers.
The exotic fruit fly threats
Three species present in Papua New Guinea pose a particular risk: Melon fly (Zeugodacus cucurbitae), New Guinea fruit fly (Bactrocera trivialis), and the highly destructive Oriental fruit fly (Bactrocera dorsalis).
Risk analysis of the Oriental fruit fly alone, is that it is likely to have a wider host and climatic range than our Queensland fruit fly. Should it establish in Australia, it would threaten over $4 billion in horticultural production.
Monitoring on Torres Strait islands
To monitor the presence of these flies in Torres Strait, the Australian Government funds an exotic fruit fly trapping program across many of the islands. Traps operate permanently and are managed more frequently during the wet season. The detection of any of the target species triggers response activities, in a similar way to responses staged when fruit flies are detected in a pest free area.
Aided by wind, small numbers of exotic fruit flies arrive on the northernmost islands in Torres Strait, Boigu, Dauan, and Saibai. Being located less than 10 kilometres from the coast of Papua New Guinea, Australia has in place proactive control measures on these islands from November to May.
Islands towards the centre of Torres Strait, such as Badu Island, Moa Island and Yam Island see occasional detections. These islands are located some 50 kilometres from the Australian mainland and response activities are directed on an as needs basis.
It is very uncommon to detect exotic fruit flies on the islands closest to the Australian mainland, including Thursday Island and Horn Island. However, given the proximity to the mainland, the detection of even a single exotic fruit fly prompts response activities on all islands in the area and additional monitoring on the Australian mainland.
It makes sense to stop the flies while they’re only on the islands. Should exotic fruit flies make their way to the Australian mainland, their first port of call would likely be in Cape York Peninsula. Given how remote and inaccessible this area is, a large-scale eradication response would be extremely difficult.
Since most of the islands in Torres Strait are Australian territories, eradication efforts in the Torres Strait are dealt with under the provisions of the Emergency Plant Pest Response Deed (EPPRD). A three-year rolling response plan under the EPPRD has been agreed between Parties, including the Australian Government, the Queensland Government and horticultural industries.
When response activities are required it is the Queensland Government that swings into action, coordinating additional traps, protein bait sprays, and male annihilation technique to eradicate any incursion.
These activities are funded under the provisions of the ERPPD. There is a pre-approved budget of $400,000 per financial year, paid for by Parties to the agreement. Horticultural industries contribute 20 per cent of this response budget, the rest being cost-shared between governments.
A good investment
An Oriental fruit fly incursion has happened before, giving us an indication of the cost of an exotic fruit fly incursion. In 1995 the species was found in Cairns – at that time it was called Asian papaya fruit fly. The subsequent eradication program lasted five years and cost governments and industries $36 million. Affected industries also incurred losses of $100 million in lost trade and additional quarantine treatments.
A review by ABARES also demonstrated the overwhelming cost-benefit of the ongoing eradication program. In 2013 ABARES estimated that the investment delivered a benefit-cost return between 169:1 and 1063:1, depending on the likelihood that eradication could be achieved.
Producers can be assured that their contribution to the eradication effort is a worthwhile investment.
Plant Health Australia is the not-for-profit coordinator of the government and industry partnership for biosecurity in Australia. More at planthealthaustralia.com.au
The National Fruit Fly Council brings together government, researcher funding groups and growers to develop a national approach to managing fruit flies in Australia. More at preventfruitfly.com.au/national-coordination/national-fruit-fly-council/