Insects heading to Windhoek soon
Biological control measures will be introduced in a bid to control the destruction caused by three invasive cacti species.
04 February 2019 | Environment
With large areas of the capital already infested by three invasive cactus species, various avenues are being pursued to prevent further spread thereof.
One avenue being explored, is the introduction of a biological control measure against these plants. In this vein, stakeholders held a public meeting in November last year where interested parties could raise their concerns.
At the meeting, one concerned member of the public, Abraham Kanime, asked what the impact of these proposed insect species would have on local animal species. The team assured him that there would be no impact. “These agents will hopefully become part of the ecosystem, reducing the density of the cactus pests and providing permanent control. Neither the cactus nor the agent will ever completely disappear. There will always be some cacti, but they will also have populations of the agent on them. The aim of biological control is to reduce the cactus population density to below a damage threshold so that it is no longer a pest,” according to the Scoping report that was released in January.
The impact on other plant species have also been taken into consideration. “Over 100 years of similar work in South Africa and Australia have recorded no impacts on untargeted species.
“Monitoring by NUST students will be included in the project, as a safeguard for early detection of potential problems,” the report read.
The Namibian Chamber of Environment, together with the Botanical Society of Namibia and the Rhodes University Centre for Biological Control, are aiming to release three host-specific insect species to control infestations of these specific cactus species that are invasive. The pro-blematic cactus species are the Imbricated, Pest Pear and Snake cacti.
According the background information document, these cacti are likely to spread and invade other parts of the country if control measures are not implemented.
Gunhild Voigts, a representative of the Cactus Clean-up Initiative, said that although a cactus plant is already dying it is likely to activate a lot of generative and vegetative propagation beforehand. She said that even if a cactus is dead, it still has to be removed physically. In reaction to her worries, the team said that mechanical clearing is a vital strategy to control invasive alien cacti and should be continued. “Communication between biocontrol practitioners and mechanical clearance teams is important because mechanically clearing of areas where biological control is established should not take place,” they said. Other residents were on board with the proposal and appealed to government to approve the importation of the insects to help control the spread of cacti all over the country.
It was recommended that an Environmental Clearance Certificate be issued for the proposed project, on condition that a number of criteria be met. This includes that the necessary phytosanitary permits and customs approvals are obtained and the necessary precautions are taken to prevent accidental clearing of the growing population stocks that are released in Windhoek. The establishment and growth of the populations of biocontrol agents should be carried out, ideally involving local students. This will build experience and capa-city in the important field of biological control.