In an effort to rescue Fraser Island’s pandanus trees from the devastating effects of infestation by Jamella leaf-hopper (Jamella australiae), 26 October saw the long-awaited release around Eurong of a tiny sandfly-sized predatory wasp (Aphanomerus sp.) that is expected to help to check Jamella numbers.
Queensland Parks and Wildlife Service (QPWS) Principal Ranger Ross Belcher reported that University of the Sunshine Coast environmental science student Joel Fostin, with QPWS, released ~500 captive-bred wasps onto Jamella egg clusters at Eurong, One Tree Rocks and Lake Wabby. Subsequent releases are planned for Dundubara, Waddy Point and Dilli Village. Funding for this project comes from QPWS, with support from the Fraser Coast Regional Council, Fraser Island Defenders Organisation (FIDO), the Fraser Island Alliance and other stakeholders. All areas will be monitored for rate of spread and the effectiveness of the control.
The Jamella leaf-hopper, native to north Queensland, was accidentally transported to southern Queensland in the 1990s on infected plant material. In the north of the state, leaf-hopper numbers are controlled by the Aphanomerus wasp, which exclusively lays its eggs in leaf-hopper egg rafts, where immature wasps eat the developing Jamella. Released from predation, Jamella numbers skyrocketed, with devastating results for the pandanus populations of southern Queensland, including Fraser Island.
Biocontrol of Jamella by introduction of the wasp has been effective in other parts of SE Queensland and northern NSW, and QPWS has been applying to release the biocontrol wasp since 2011. The biocontrol responds to the Jamella outbreak by slowing down in cooler months and increasing numbers in warmer active months. The wasp has only 7–9 days to find a Jamella egg raft in which to lay its eggs.
The wasps released on Fraser Island were bred in sterile conditions by Joel Fostin from wasps collected from the Sunshine Coast and were fed on Jamella egg rafts, collected from Fraser Island. Once established at the release sites, the wasps can be relocated across the island. In combination with continued stem injection pesticide treatment, it is strongly anticipated that this step could spell a return of the iconic Fraser Island pandanus community to its former glory.
Adapted from Media Release from QPWS