Tiny wasp released to save Fraser Island’s pandanus
Oct 29, 2015
A tiny wasp could save the iconic pandanus trees of Fraser Island (K’Gari).
The island’s pandanus trees have been devastated in recent years by Jamella, a small leaf-hopper insect, but the release of a sandfly-sized native wasp around Eurong is the first stage of rescuing the plants.
The project has been funded by the Queensland Parks and Wildlife Service (QPWS), and is supported by the Fraser Coast Regional Council, Fraser Island Defenders Organisation (FIDO) and the Fraser Island Natural Integrity Alliance (FINIA).
QPWS Principal Ranger Ross Belcher said University of the Sunshine Coast environmental science student Joel Fostin with QPWS released the captive-bred wasps onto Jamella egg clusters at Eurong, One Tree Rocks and Lake Wabby on 26 October.
“The distinctive pandanus are an important feature of the coastal landscape from Rainbow Beach to Coffs Harbour, but the Jamella leaf hoppers have been causing their decline since being accidentally introduced to southern Queensland in the early 1990s,” Mr Belcher said.
“We know this little wasp keeps Jamella leaf hoppers in check in the northern part of the state, so hopefully they help contain the problem down here,” he said.
The wasp, Aphanomerus sp, lays its eggs only in the leaf-hopper’s egg rafts where immature wasps eat the developing Jamella.
FIDO’s John Sinclair welcomed today’s release of the predatory wasp.
“Once the wasp is established on the island, this biological control that has been effective in other parts of south-east Queensland and northern NSW, in conjunction with chemical injection treatments used for more than a decade, should return the island’s pandanus to their former glory,” Mr Sinclair said.
The flatids or pandanus leaf hoppers Jamella australiae suck the pandanus sap from the leaf sheaths and exude honeydew. This sugary substance encourages the growth of mould, and the terminal growth points of the leaves then rot, especially if the trees are already stressed by other environmental factors.
Jamella has been a problem across SE QLD and northern NSW coastal pandanus communities since being introduced in the early 1990s via an infected plant from north Queensland. The predator wasp didn’t survive the same journey, giving the flatid an unchecked head start on the southern pandanus populations.
Both the flatid and wasp are native to north Queensland. The flatid is 2mm to 8mm in length fully grown and the adult wasp is tiny, just 2mm fully grown.
Their relationship is symbiotic, but not on equal terms, with the wasp reliant on the flatid eggs hosting its larvae. The wasp appears entirely dependent on the flatid for its reproduction and survival. The climate in SE Qld is thought to be at the limits of the wasp’s capacity to survive.
Treatment of pandanus affected by the leaf-hopper has historically been through stem injection pesticide treatment. This is reasonably successful, but extremely onerous, and it is difficult to access all plants in coastal areas. QPWS practises this control method in various parks across south-east Queensland, including on Fraser (K’gari).
The wasp has been introduced by councils and catchment groups, for example in northern NSW, Redland (including North Stradbroke Island), Sunshine Coast and Bundaberg. It is already present in Great Sandy National Park, in the Cooloola section.