Cochineal soldiers on the march

Posted 23 March 2020.

Natural Resources South Australian Murray-Darling Basin (SAMDB) together with landholders and a tiny insect are tackling the hard to control spiny incursions of common prickly pear (Opuntia stricta) and wheel cactus (Opuntia robusta) in the Riverland.

Natural Resources SAMDB Riverland Senior District Officer Jodie Woof said we are releasing cochineal insects, a biological control for opuntioid species at selected trial sites across the Riverland, to breed some nursery areas of the bug to aid the control of large cactus infestations across the Riverland.

“Natural Resources SAMDB district officers have been collecting the cochineal insects from previously established populations in Nildottie and are working with landholders at trial sites to attach and spread the biological control agent to invasive cactus populations,” Ms Woof said.

Gurra Downs date farmer Dave Reilly said the cactus infestation on our property is situated across large amounts of undulating country which is inaccessible by vehicle and contains sensitive sand dunes interspersed with native vegetation, so chemical or manual control is not practical to use in these areas.

“The cactus is spreading rapidly by animals dislodging the pads from the plants so the weed is popping up in new spots such as the adjoining floodplain,” Mr Reilly said.

“Using a biological control method is the best option for this situation as the insect only feeds on the cactus, working away in the background to reduce the plant health and vigour.

“Our property is a trial site to see how the cochineal insect grows on this type of cactus. In time, it may become a nursery site where the microscopic insect will be collected and shared with other landholders who have cactus infestations.

“I’m very pleased to work with Natural Resources SA Murray-Darling Basin Riverland District team, and I applaud them for their efforts regarding opuntia control,” Mr Reilly said.

“While biological control may not bring rapid results like more expensive mechanical and chemical control, it does mean that we can rely on nature to spread it into areas we can’t reach, like hard to get to places such as Mr Reilly’s sand dunes or terraced river areas,” Ms Woof said.

“Autumn and spring are the best time of year for cochineal release, we are trialling a cochineal species which is host specific to these problematic cacti plants.

Prickly pear was first brought to Australia in the late 1700’s to start a cochineal (red) dye industry, then planted as garden ornamentals or hedges.

Many species of cactus have escaped or been left to spread around old homesteads, which are difficult to control and impact both the environment and primary production.

Prickly pear and wheel cactus are declared weeds under The Natural Resources Management Act 2004.

For more information on controlling cactus, contact your local Natural Resources office or the Natural Resources Centre, Berri on phone 8580 1800.

This program is supported by the SA Murray-Darling Basin Natural Resources Management Board through funding from the NRM levies.

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