A prickly problem

05 July 2018

It’s not every day an insect is described as “an absolute godsend”, but for Peter and Elizabeth Clark the cochineal biocontrol agent D. tomentosus (‘cholla’ biotype), aimed at controlling boxing glove cactus (Cylindropuntia fulgida var. mamillata), is exactly that.

For almost 40 years the Longreach producers have worked tirelessly and invested more than $250,000 on herbicide and predator fencing in attempts to control their cactus problem. They run 3,000 Merino sheep on 11,000ha.

Herbicide had to be applied “until the plant was dripping” and predator fencing was aimed at reducing cladode (the flattened stem of the plant) spread by kangaroos and goats.  

However, the couple admitted that prior to the biocontrol agent release on their property in March 2016, they were barely holding ground.

“It’s basically a pot plant gone wild,” Elizabeth said.

“It’s been around here since the 1960s but it took a long time for the community to realise it was a problem. It took even longer to correctly identify it and work out how to tackle it.”

Elizabeth said the plant’s toughness, ability to thrive in dry conditions and to reproduce prolifically makes has created a control challenge.

“It’s relentless. We had a patch we sprayed four times, we couldn’t spray it one year and it got away on us again,” she said.

“Dense plantings are also difficult to spray effectively and if you don’t spray the entire plant to run-off, it won’t die. It’s also very easy to miss juvenile plants.”

The biocontrol project

In March 2016, Elizabeth and Peter became enthusiastic participants in a new collaborative biocontrol project, funded by Australian Government Department of Agriculture and Water Resources as part of its Rural R&D for Profit program, MLA, NSW Department of Primary Industries and the Queensland Department of Agriculture and Fisheries. The project was also led by MLA.

Led by Andrew McConnachie, weed biocontrol research leader for NSW DPI, the project staged its initial release of D. tomentosus (‘cholla’ biotype), a cochineal (a type of sucking scale insect) on boxing glove cactus at Leander Station.

“We did a single release on a 1ha test plot and, within 16 months, 100% of those plants were infected with cochineal and 95% of the plants had died,” he said.

Andrew said the method of release was just as important as the species of cochineal to this biocontrol success story.

“Cochineal are spread by the wind, they’re blown from one plant to another, so it’s important to place them on the upwind side of the plot,” he said.

“It’s also horses for courses. Cochineal is a very effective control agent on dense plots but less effective on sparse plantings where it is more difficult for the insect to infest the next cactus.”

In late 2017, the project released another cochineal biotype (D. tomentosus californica var. parkeri’) at two Hudson pear sites in northern NSW and has made a further 34 releases of D. tomentosus (‘cholla’ biotype) on boxing glove cactus at sites across Queensland, WA and NSW.

Andrew said the Queensland Department of Agriculture and Fisheries recently released another cochineal biotype (‘bigelovii’) on snake cactus and there are plans afoot to release the ‘acanthocarpa X echinocarpa’ biotype on brown spined Hudson pear and the ‘cylindropuntia’ biotype on pencil cactus and Klein’s cholla.

Taking control

It is estimated more than $250 million/year could be delivered in productivity gains and cost savings following the introduction of biological control agents for six of Australia's invasive weeds.

'Natural enemies' such as insects, mites and diseases to control parkinsonia, parthenium, blackberry, silverleaf nightshade, cylindropuntia and gorse, which affect more than 25 million hectares across Australia,  have been introduced through the Rural R&D for Profit programme's Fast-tracking and maximising the long-lasting benefits of weed biological control for farm productivity.

The three-year project was managed by MLA working with national and state based research organisations, universities, Landcare groups and local management authorities.

In addition to individual projects focusing on the six weeds, the project also delivered a new partnership model to ensure the ongoing funding and prioritisation of weed biocontrol and the development of the online Biocontrol Hub and supporting smartphone app.

This project is supported by funding from the Australian Government Department of Agriculture and Water Resources as part of its Rural R&D for Profit programme.

More information

Find the Biocontrol Hub at: biocollect.ala.org.au/biocontrolhub

Email Peter and Elizabeth Clarke

Email Andrew McConachie

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