WHEN it comes to weed control, wheel cactus is a prickly subject. 
It is a declared noxious weed in Victoria and landowners have a legal responsibility to control weeds on their property. Weed control is important for local communities - it helps to protect the natural environment and preserve biodiversity. 
The spread of wheel cactus is a significant problem throughout Victoria, mainly in the north. It is a highly invasive weed that can quickly spread and take over large areas of native vegetation and productive farmland, also impacting the health of our environment and native wildlife.
Wheel cactus spreads from uncontained sites and is an introduced species from Central America. 
The weed is easily identified by its very round-shaped lobes, while most of the other prickly pear (Opuntia stricta) species have more oval-shaped lobes. Wheel cactus also has a distinct bluey-green coloured flesh, with yellow flowers and large, purple-red fruit.
Wheel cactus seeds are spread by birds, animals and by the elements. It is an extremely aggressive invasive weed that can take over pastoral and agricultural lands if not controlled.
Some different methods and tools can be used to destroy wheel cactus plants, depending on their size, maturity and density. 
They need to be destroyed before they start to flower and bear fruit to avoid further spread. The seeds from mature plants can germinate for up to 20 years. 
The plant lobes have waxy skin and don’t absorb surface sprays, so the most effective treatments are by digging and burying smaller plants, or injecting larger plants with herbicide. Wheel cactus will regenerate from any single piece of lobe so it cannot be dug up and left on the ground.
Wheel cactus plants are very easy to remove manually because they are very shallow-rooted.
Plants removed manually should be destroyed by incineration, however, most plants contain too much water for this to be a successful method, unless they are small, very dehydrated or you can create an extremely hot fire. Manually removed plants can be buried, but need to be covered with 50cm soil and buried. Medium to large wheel cactus can be killed by Injecting all outer and second wheels (lobes) with herbicide. Injecting more lobes increases the chance of a faster knockdown  and successful control.
 It is important to wear protective clothing to stay safe and healthy while using herbicides.
A promising biological control method for wheel cactus (opuntia robusta) is cochineal insects (Dactylopius species). These herbivores attach to the outside of the host cactus plant and feed by sucking moisture from it. The insect appears as tiny black dots on the pads and is more regularly recognisable by the white waxy and fluffy-looking substance produced by the juveniles as a casing to protect themselves. 
The cochineal biological control may take years to become established enough to have any significant effect so all mature  
Wheel cactus plants must continue to be killed using current techniques. Hopefully, in the future, the use of cochineal biological control will be an additional tool that can be used in combination with current methods. 
Previous use of the insect as a biological control agent in South Australia has seen a strong impact on the wheel cactus in terms of die-off and slowed growth. 
While not proven to take out large infestations, the small release site on Mt Buckrabanyule is adding another dimension to tackling this weed. The progress of the insect will be tracked and if the population grows large enough, will be released to more sites on the mountain.
As a community, we all must take action to stop the spread of this weed. We must spread the word, not the weed. 
We can also join local volunteer groups to help control its spread and work with local land managers to help identify and remove affected areas. We can all show our support by signing petitions, writing letters to our politicians and local councils, and supporting organisations that are actively working to tackle this weed. We must all unite and take action to help stop the spread of Wheel cactus. 
Through the Loddon Plains Landcare Network, and its member groups, such as the Wychitella and Districts Landcare, Landcare has been working hard to tackle the issue of weeds in the region. 
Their efforts have focused largely on the slopes of Mount Buckrabunyule, but have extended to other areas of the region as well. A variety of techniques have been employed to try and eliminate the weeds, such as the use of herbicides, manual removal, and the introduction of native plants. Landcare’s efforts have made a huge difference to the Loddon Plains, and have been crucial in ensuring that the region remains a healthy and beautiful environment for years to come. 
Network facilitator Will Sanson says: “Landcare takes a collaborative approach to promoting sustainable land management practices in its local area. 
“The organisation works closely with farmers, landowners, and other community members and will provide education and support for weed control,” he said. 
“We are planning an information field day and will invite all members of the community to attend. This event will be an opportunity to learn more about Cactus control”. Mr Sanson said.
- ANDREW PERRYMAN