A biological control for coral cactus could be less than six months away.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 3 minutes 18 seconds 3 m 18 s Entomologist and a landholder discuss a biological control for coral cactus ( Lydia Burton ) Download 1.5 MB

The weed that is found in most states in Australia, including New South Wales, South Australia, Western Australia and Queensland, is currently controlled through labour intensive methods like spraying it with herbicide or digging it out.

But after four years, senior entomologist Michael Day said he was trialling an insect in a Brisbane laboratory.

He has been visiting Longreach properties with the infestations, to see if they could become trial sites once the insect had approval.

"Our collaborators in South Africa have found an insect which is highly damaging and controlling their coral cactus and so we have imported that particularly insect into a quarantined facility in Brisbane and we have tested it against species in Australia to make sure it is safe there, prior to us releasing it in Queensland," he said.

"The testing is all complete and we have applied to Canberra to release the agent in Australia.

"At the moment the feedback from Canberra is that they believe it is also safe and worth releasing but we need to go through the protocols and procedures, which could take another six months before approval is finally granted."

Coral cactus plants are carried and spread easily by stock and kangaroo movements. They thrive in the arid soils around Longreach, Ilfracombe and Blackall. The pictured infestation is at a cattle property south of Mount Isa.

Mr Day said the insect known as 'cholla' being trialled was host specific.

"Both the adults and its juveniles suck the sap and in doing so it actually opens up," he said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 3 minutes 46 seconds 3 m 46 s Entomologist Michael Day on biological control for coral cactus. Download 1.7 MB

"[The insect can then] transfer diseases in the salvia and it [sucking the sap] can also open up wounds in the plant to other natural pathogens causing the plant to rot.

"In the lab insects placed on potted plants have killed these plants in 18 weeks.

"That gives us a bit of an idea of what could happen in the field but it doesn't really relate to the large infestations that we are seeing on some of the land in Queensland.

"It is a little a bit harder to transfer those time periods because the infestations are so large."

Mr Day warned it may not be the 'silver bullet'.

"We are optimistic, but nature has its funny ways of finding us out if we are too optimistic so we are cautiously pleased," he said.

Landholder welcomes biological control

Peter Clark from Leander, north-west of Longreach, has about 500 hectares of coral cactus on his 12,000 hectare property.

Mr Clarke has been providing Michael Day's lab with samples of coral cactus to test the 'cholla' biotype, the insect being trialled.

He said he had been trying to control the weed for over 20 years and had spent more than $100,000 on control methods.

"It [coral cactus] has a great ability to spread, it can grow in any sort of country, it is difficult to see," Mr Clarke said.

"It will get into the scrub and everywhere else and if it gets let go it will just grow thick and it is pretty impassable to get through it."

Mr Clark said he would definitely take part in the biological control trial.

"I think it would be like Christmas coming," he said.