Biological Control Release – Australian Pest Pear | Blog
Lalibela Game Reserve has begun a project in conjunction with the Rhodes University Centre for Biological Control (CBC). The Centre for Biological Control (CBC) focuses the majority of its research on understanding the ecological dynamics of invasive pests, aquatic and terrestrial weeds in particular. The focus is the development of biological control methods for these invasive plants. Biological control is seen as a positive solution because it is not toxic, pathogenic or harmful to humans.
We have begun releasing a biological control agent in June of 2021 against a particular species of cactus called the Australian Pest Pear (Opuntia stricta). It is an alien invasive cactus species indigenous to the USA that was extremely problematic in Australia prior to it being controlled using biological control. It is not known when it was introduced into South Africa but it is assumed that it was imported by succulent collectors. The Australian Pest Pear is a low sprouting shrub, approximately 1 meter tall with blue-green flattened stem segments or leaf pads that become narrower at the base. Yellow flowers, approximately 5 -6 centimetres in diameter give rise to dark-red or purple pear-shaped fruits. Wild animals, particularly baboons and elephants eat the fruit and spread the seeds through their dung across the reserve. This then spreads the invasive species across other areas of the reserve.
The species of biological control agent is a cochineal insect (Dactylopius opuntiae ‘stricta’) that can only feed on the Australian Pest Pear (Opuntia stricta) and a few very closely related cactus species, none of which are indigenous or valued in South Africa. Cochineal insects are sap-sucking insects that feed only on cactus species (plants within the family Cactaceae). It is therefore an environmentally friendly way to control the cactus species without harming any other plants.
The Conservation team at Lalibela Game Reserve have identified areas of the reserve that are infested with this species of cactus and in the past chemical control has been the means of eradication. We have started this project to clear the invasive cactus from our conservation area in order to bring back the natural indigenous vegetation, as well as to make the environment safe for all species to thrive.
We have currently released the biocontrol agent in two distinct areas of the reserve that have a high concentration of the Australian Pest Pear. The process involved releasing parts of the cactus infected with the biocontrol agent that was bred by the CBC at their mass-rearing facility in Kariega (previously known as Uitenhage) which is situated close to Port Elizabeth. The infected biocontrol agent is then placed in the areas heavily impacted by the cactus. This will create a breeding area of these biological agents that can be distributed to the rest of the infected area.
This process will take a couple of years and is left to the Cochineal insects to breed and spread and hopefully in a few years time we will have successfully controlled the Australian Pest Pear on the reserve. We will be working closely with CBC staff and students to do research and follow up releases on the reserve and are grateful to the Department of Forestry, Fisheries and Environment: NRM programmes for funding the CBC’s activities. This Conservation Project is a strong commitment from us to protect our environment for future generations and educate our visitors and communities on the importance of nature for all to enjoy.
In search of more reading? Here’s South Africa’s Eco Warrior – The Spekboom
Lalibela Game Reserve is located in the Eastern Cape of South Africa, close to Port Elizabeth and Addo, which means it is not only malaria free, but spans 5 ecosystems, resulting in a breath-taking diversity of flora and fauna.