Combating cactus with cochineal
Cochineal is showing promising signs of being an effective biological weapon to assist land managers and volunteers tackle Opuntia infestations in the northern Flinders Ranges.
Posted 04 April 2018.
Traditionally harvested for its natural dye carmine, cochineal (Dactylopius coccus) - a scale insect native to North America – it is proving effective in tackling Opuntia species, prickly pear, devil’s rope and wheel cactus, across the region.
With a number of volunteer groups and landholders involved in cactus control programs, the Blinman Parachilna Pest Plant Control Group (BPPPCG) hosted a Control Strategy meeting in late February to map infestations regionally and coordinate control plans for the next 3-5 years, with cochineal featuring as a key biological tool in tackling the pest species. The SA Arid Lands NRM Board supported the BPPPCG in sourcing funding for the event through the National Landcare Program and providing logistical and mapping support.
Guest speaker Peter Jones from Biosecurity Queensland, a leading authority on using cochineal as a biological control, also shared information and advice on cochineal, including the importance of establishing a nursery facility, in or around Blinman, for the protection and multiplication of locally successful strains of cochineal. This would provide a convenient supply of the bio control for spreading by volunteers and also ensure there is a back-up population if events such as heavy rains deplete existing naturally spreading cochineal populations.
Bill McIntosh from Gum Creek Station says the use of cochineal could be a game changer for tackling cactus infestations, particularly in areas of difficult terrain that are hard for volunteers and equipment to access.
“Traditionally we have relied on injecting cactus with glysophate,” Mr Mcintosh said. “This is costly and requires many volunteer hours as well as logistically having to coordinate and carry additional water and chemicals to refill backpacks. This always complicates the huge task of getting to Opuntia populations in all of the inaccessible areas it now occupies.”
And while cochineal is not an instant fix to the problem, Mr McIntosh says he is very heartened by the results so far. And with the group now having learnt more about the insect, and the importance of protecting healthy viable populations of cochineal, he is optimistic that it will offer a long term option to control Opuntia, particularly in the wooded and undulating areas of the ranges.
“Even though the advent of successful bio control strains have emerged, I believe we still have to pick where we are able to fight it with chemical and where we have to leave it to biocontrol…. This dual strategy is going to be the most effective way of ensuring the cactus menace is both minimised and ultimately contained in this area”.
“There is a lot of effort we have already put in to cactus control and hopefully people can look back in 15 years’ time and say ‘that really made a difference’,” he said.
Outcomes from the day included the need to implement a monitoring strategy at sites where Opuntia had been treated with either glysophate or cochineal to remove any new plants for up to five years and investigating establishing an enclosed cochineal nursery in Blinman to eradicate threats to the cochineal breeding populations from weather and predation by insects.
Information about Cochineal:
• The insect has a 55-day breeding cycle, producing 2000 offspring each cycle
• Live on succulents and feed on sap, effectively sucking the plant dry and killing it
• Cochineal is active in its lifecycle but are less active in winter months. Rain can wash the insects away or drown them.
• The reproductive fitness can vary and it’s important to protect and spread these productive strains. This fitness varies within a population and can affect development success, development time and number of eggs laid over a lifetime.
• Predation from ants and beetles can impact cochineal. Controlling ants around cactus by spreading Coopex powder around the base of the plant can help protect the cochineal long enough to allow it to establish.
• Cochineal was first released in 1920 and many strains have been released since then.
• When harvesting infected cladodes (pads), it is best to cut them off at the node to reduce the area of sap flow. Cochineal that walk onto the sap can drown. Paper can also be used to slow down the sap flow. When attaching infected pads, the cut side should be placed face down to prevent cochineal drowning.
Background
The Blinman-Parachilna Opuntia Control Group (BPPPCG) is a community group which has worked with volunteers and contractors to control pest weeds, mainly cacti, in the Northern Flinders region since 2002. Its work to control Opuntia in the region has contributed to putting cactus on the state and national agenda, helped drive funds for cactus control in other NRM regions, and influenced the listing of Opuntia cactus in the Weeds of National Significance program.
Peter Jones is an Experimentalist in the Invasive Plants and Animals group within Biosecurity Queensland. He has over 20 years of experience in working in biological control of weed projects and is one of Australia’s leading authorities in cochineal biotypes to control the eight naturalised Cylindropuntia in Australia.
Volunteer groups involved in Opuntia control in the region include the Toyota Landcruiser Club, Adelaide Bushwalkers, Mitsubishi 4WD Club, Overland 4WD Club, and Australian retired Pensioners Association Bushwalkers.
Biological control
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