Revised Distribution of Bactrocera tryoni in Eastern Australia and Effect on Possible Incursions of Mediterranean Fruit Fly: Development of Australia's Eastern Trading Block

Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), commonly called 'Queensland fruit fly' in Australia, and Mediterranean fruit fly (Ceratitis capitata Wiedemann) (Diptera: Tephritidae) are the two most economically important fruit fly in Australia with B. tryoni in the east and Mediterranean fruit fly in the west. The two species coexisted for several decades, but it is believed that B. tryoni displaced Mediterranean fruit fly. In southeastern Australia, this was deemed inadequate for export market access, and a large fruit fly free zone (fruit fly exclusion zone) was developed in 1996 where B. tryoni was eradicated by each state department in their portion of the zone. This zone caused an artificial restricted distribution of B. tryoni. When the fruit fly exclusion zone was withdrawn in Victoria and New South Wales in 2013, B. tryoni became endemic once again in this area and the national distribution of B. tryoni changed. For export markets, B. tryoni is now deemed endemic to all eastern Australian states, except for the Greater Sunraysia Pest-Free Area. All regulatory controls have been removed between eastern states, except for some small zones, subject to domestic market access requirements. The eastern Australian states now form a B. tryoni endemic trading group or block. All Australian states and territories maintain legislation to regulate the movement of potentially infested host fruit into their states. In particular, eastern states remain active and regulate the entry of commodities possibly infested with Mediterranean fruit fly. The combination of regulatory controls limits the chances of Mediterranean fruit fly entering eastern states, and if it did, Mediterranean fruit fly is unlikely to establish in the opposition to a well-established B. tryoni population.