Esperance-based department senior biosecurity officer Darren Dixon inspecting prickly pear. Photo: DPIRD.

Scale insects control cactus infestation in Esperance

Scale insects which the Department of Primary Industry and Regional Development released as biological control agents are helping wipe out damaging cactus infestations in the Esperance region.

Working alongside local farmers and biosecurity groups, the department released the Dactylopius coccus cochineal in April 2016 to control cactus infestations occurring along rivers, roadsides, rail sidings, old homesteads and farm paddocks.

The program has enjoyed remarkable success in minimising damage to established plant species and injury to stock, humans and native wildlife.

Originally from North America, the cochineal controlled the final drooping pear infestation (Opuntia monacantha) on the Oldfield River in December 2019.

It has also helped significantly reduce prickly pear (Opuntia stricta) infestations in the Scadden area, allowing farmers to kill off any remaining plants with targeted herbicide applications.

The department has been engaging with growers in the affected region to coordinate efforts.

Staff have also worked with local contractors, the Tjaltjraak Aboriginal Rangers and the Southern Biosecurity Group in activities on the Oldfield River.

Esperance-based department senior biosecurity officer Darren Dixon said many farmers were initially sceptical of biocontrol methods but now welcomed the positive changes the cochineal had brought.

"It gets right into the cactus, stops it flowering and dramatically reduces the number of fruit produced," Mr Dixon said.

"The scale attacks the cactus leaf pads and stems and sucks all the moisture from the plant, causing them to yellow and eventually die.

"Biocontrol options remain the most cost-effective and practical way to control widespread and established infestations of cactus species and offer almost cost-free control to the landholder."

The scale spreads naturally via the wind or farmers transporting infected plants to uninfected areas.

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