Biological control to aid battle against Opuntia cacti species
05 December 2019
Thousands of hungry Cochineal scale insects have been released by Natural Resources Officers at seven Opuntia cactus outbreak sites near Cleve, Cowell and Kimba, with a strong focus on the Birds-eye Hwy section between Cleve and Cowell, to curb the spread of invasive and introduced prickly Opuntia plants.
The release is part of the Eyre Peninsula Natural Resources Management Board’s targeted biological control program primarily concentrating on the Indian fig, but also effective against multiple Opuntia species including the common prickly pear and wheel cactus, on eastern Eyre Peninsula.
Natural Resource Officer Rebekah Davenport said that using Cochineal as a biological control is a cost effective and long term solution to reduce Opuntia population size and prevent further spread.
“Opuntia species are classed as declared weeds and require management to reduce impact on native ecology and agriculture.
Releasing Cochineal, a scale insect that sucks nutrients and moisture from the plants which dehydrates and kills them, is one method of control that can be used.
Each species of Cochineal is specialised in feeding on certain species of Opuntia and the insects do not pose threats to any other types of plant.
The insect appears as tiny black dots on Opuntia pads and are more regularly recognisable by the white waxy and fluffy-looking substance produced by the juveniles as a casing to protect themselves” Ms Davenport said.
Populations of Opuntia plants compete directly with native vegetation. Their spiny exterior and dense growth commonly forming thickets which then limit access to fence lines and impede livestock, human, and native fauna access to water and food sources. These thickets also provide harbor for pests such as rabbits and the fine spines can easily penetrate human skin and cause severe irritation.
“We are hoping that the Cochineal will establish well on these Opuntia populations and provide a source that can be transported to other problem sites across Eastern Eyre communities and beyond on both public and private lands.
“We’ll be monitoring the Cochineal populations closely over the next few months to see how well the insects take to their new environment. Using biological control is a slower process than chemically treating the plants but can have a much greater reach. Cochineal are known to naturally spread a few kilometres from releases sites, however, success of spread is reduced the further apart Opuntia populations are within the landscape.
If you have any questions about the release or notice Cochineal insects or casings on Opuntia located on private land nearby release sites please don’t hesitate to contact Natural Resources EP Cleve Office on 8628 2077, or Rebekah on 0428 282 077.
Communications and Engagement Officer