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Wasps VS Ants - bio control to eradicate Yellow Crazy Ants

YCA Scale DNP 1100
As many of you know, invasive yellow crazy ants have posed a serious threat to Christmas Island’s wildlife, the red crab population in particular, but it looks like scientists have finally found a solution: a micro-wasp from Malaysia.

After more than seven years of research, community consultation, and biosecurity checks, the first batch of micro-wasps have been released in Christmas Island National Park to control yellow crazy ants.

The baby wasps, growing inside parasitised scale insects, were bred in captivity in Malaysia. At the end of January this year, they were released into the forest canopy into a yellow crazy ant super-colony. The wasps will feed off the yellow crazy ants’ major food source to reduce the size of the super- colony. This video explains how it works:

The yellow crazy ant is listed as one of the world’s 100 worst invasive species by the International Union for Conservation of Nature. Parks Australia and La Trobe University have worked for years on this biocontrol project to ensure it has the best possible chance of success.

La Trobe University ecologist Dr Pete Green said descendants of the initial batch of wasps have just been released.

“The adult female wasps have been laying their eggs inside scale insects inside our control area,” Dr Green said. “So we’ve actually taken these insects with the larval wasps inside and hauled them into the rainforest canopy 20 metres above the ground using fishing line.

“The wasps are now due to hatch before mating and looking for new scale insects to lay their eggs. Further batches of the insects will be released on parts of the island where there are crazy ant super-colonies and suitable scale insects.

“Park rangers and scientists will carefully monitor these test sites to see how the wasps are adapting to their new environment, and how well they are reducing the numbers of scale insects and crazy ants over coming months and years.”
YCA Scale Image Dr Pete Green 1100

The 2mm wasp won’t attack the ants directly, but will instead target scale insects which produce honeydew – the ants’ major food source. The wasp does not sting or build nests and it will not harm people, pets, plants or other wildlife. There are already many similar micro-wasps on Christmas Island and they’re not causing any problems. Unfortunately, none of them target lac scale insects.

Director of National Parks, Sally Barnes, said yellow crazy ants were a serious threat to Christmas Island’s wildlife.

“Since the ants started to form destructive super-colonies 20 years ago, they have killed tens of millions of red crabs and taken over large parts of the island’s forests,” Ms Barnes said.

“Their presence changes the structure of the forest and up until now our only option has been to poison bait the crazy ant super-colonies every few years. This is not a long-term solution. It’s very costly, and the ant numbers can quickly rise again. Biocontrol is a sustainable solution.”
Yellow crazy ants DNP 1200 2

Biocontrol has proved to be a solution to many of Australia’s agricultural problems from the prickly pear to mimosa in the Top End. This is not the only biocontrol project underway in Australia. Researchers are looking at a control for European carp in the Murray Darling river system.

An effective biocontrol for Christmas Island National Park will significantly reduce the costs of containment, while finally targeting these terrible pests and the impact they have on the island’s land, animals and communities.

A side-benefit of the introduction of the new micro-wasp could be to improve horticulture by controlling the scale insects that attack fruit trees and other plants on the island. The scale insects also kill large forest trees and smother the understory with sooty mould so with their removal the whole forest ecosystem will have a reprieve.

For more information on the biocontrol program, visit the Parks Australia website, and for information on the assessment process visit the Department of the Environment and Energy website

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