Coral cactus biocontrol release by end of year

Coral cactus biocontrol release by end of year

Agribusiness
A snake cactus outbreak at Longreach.

A snake cactus outbreak at Longreach.

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LANDHOLDERS battling dense infestations of coral cactus in Queensland’s rangelands could have a new ally by December.

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LANDHOLDERS battling dense infestations of coral cactus in Queensland’s rangelands could have a new ally by December.

Biosecurity Queensland officer Peter Jones told last week’s Queensland Weed Symposium in Longreach a cochineal insect was showing good promise.

One female inoculated onto a greenhouse plant “turned it to mush” after 18 weeks.

“It likes heat and doesn’t like rain, so we hope these results translate to the field well,” he said.

The insect was imported from South Africa in 2012 and has been subject to a battery of rigorous testing in quarantine since then.

“We found it didn’t feed on any plants other than this cactus, nor did it survive or lay eggs on any others,” Mr Jones said.

“We’re now aiming to see if coral cactus can support a colony of cholla, and if they can kill it.”

He said he was not sure how it would be spread, whether some manual intervention would be needed or whether crawlers would move between plants by themselves.

“Stock movements could help them out,” he said.

Toxins in the saliva of the insect that are injected into the tissue of the plant when its feeding are responsible for the cacti’s destruction.

One female can lay 1200 eggs, giving it the potential to do a lot of damage.

This was good news for Longreach graziers Peter and Elizabeth Clark, who have been battling a huge infestation at Leander, north of the town, for 15 years.

Not so good news was at hand for nearby graziers Ross and Michelle McPherson, who have been grappling with the prickly problem of snake cactus at Bexley.

Mr Jones said it was the only species they didn’t have a biocontrol agent for.

The McPhersons have been attacking the escaped garden plant with Access and with fire, and are now using Garlon.

AgForce general policy officer Marie Vitelli said it had resisted many control attempts and its extreme spiky nature made it difficult for people to work in.

“We are all perplexed at what to do next,” she said.

“This is a learning for why it’s so important to jump on outbreaks early.”

The Department of Agriculture’s Jenny Milson added that there was a big push for waterwise plants, which included succulents, and it was important to target awareness of potential damage at nursery level.

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