A twenty year battle costing $200,000 could be at an end for Longreach graziers Peter and Elisabeth Clark, and others like them, who have been waging war on coral cactus.
In an Australian first, the state government last week released sap-sucking bugs specially bred in Queensland for the express purpose of controlling the destructive plant, on the Clark’s property.
“It was a good day,” Peter said. “We’ve got 1000ha affected and it grows anywhere, on bark and stones.
“Roos were spreading it before we fenced, and you’d get a big storm and have tendrils drop off, and away it would go again.
“If the bug does what they say it will, we should be able to control 80 to 90 per cent of ours. They say it loves the heat and the dry so it should be right at home here.”
Agriculture Minister Leanne Donaldson said scientists were confident the cochineal insect offered the best chance of combating the weed.
“Its sharp spines are a threat to farmers, livestock and working animals such as dogs and horses and it is a Weed of National Significance that can reduce access to feed and hinder mustering activities,” she said.
“Biosecurity Queensland has advised me that conventional methods of control for cactus, such as herbicides and burning, can be ineffective and expensive and are not considered feasible on a large scale.
“That is why they will be mass-rearing large quantities of cochineal insects in laboratories as a prelude to a targeted release on infested land.”
Releases similar to that in Longreach last week are planned over the next few months around Charleville, Hebel, Emerald and Cloncurry.
Biosecurity Queensland senior entomologist Michael Day said the insects were spread by the wind and because the cactus was clumping by nature, there was a logistical challenge in getting the agents out to the clumps.
“There’s a risk that they won’t land on food and will die instead,” he said. “To help with this we’ll have local biosecurity officers working with landholders and Landcare groups.
“They’re there all the time, and for people like Mr Clark, their job now will be to help move the insect rather than spraying.”
While Mr Day said the sap-suckers were no super bullet he pointed out that “biocontrol is forever”, using the cactoblastis grub as an example.
“Very little control is done on prickly pear these days,” he said. “Cactoblastis has been out there for 80 years and still doing the job.”
He added that kangaroos, which have spread the cactus, could become an agent in spreading the bugs.
“If a roo picks up a segment with the mealy bug on it and drops it elsewhere, they’ll be helping with the spread, or the segment will die rather than starting another clump,” he said.
Minister Donaldson said the government was working collaboratively with the federal and New South Wales governments and Meat and Livestock Australia on a biocontrol program similar to one now successfully controlling coral cactus in South Africa and Zimbabwe.
“The program cost has cost approximately $500,000 so far, but the benefits are expected to far exceed that,” the Minister said.
The cochineal insects are sap-sucking bugs that feed and complete their life cycle on cactus plants. No other plant species will be affected.
Biosecurity Queensland will provide cultures to other states where coral cactus is a problem as part of a national program.
