Cacti infestation out of control
Even with a biological control proposal currently under review, much more needs to be done to end the cacti infestation in the capital.
03 December 2018 | Environment
Even when a cactus is already dying, it is likely to activate a lot of generative and vegetative propagation beforehand. Gunhild Voigts, Cactus Clean-up initiative.
“Several alien invasive plants are taking over the habitat of our own vegetation in the city and spreading into the rest of the country,” says Gunhild Voigts, representative of the Cactus Clean-up initiative.
According to her, 90% of the affected areas in the capital are municipal open spaces. “The problem has not been addressed by the City of Windhoek authorities and it has now reached a tipping point. There is also no funding available from the CoW,” Voigts added.
According to Harold Akwenye of the CoW, the cacti infestation is a major problem countrywide. When asked if meetings have been held to stop the spread of these alien species, he said that Dr Ian Patterson, an expert on biological control from South Africa, gave a presentation at the Scientific Society on the benefits of biological control at the end of last year. “Various stakeholders were present, like the Ministry of Agriculture, the Namibian Chamber of Commerce and Industry, private entities and the CoW.”
However, not much came of the meeting and the last clean-up campaign the CoW did, was in 2011. “It was with a chemical treatment conducted by our Parks Division, but nothing since then due to limited resources,” he said. “However, there is some support from private individuals who conducts cactus clean up campaigns around Windhoek.”
Akwenye's advice to curb the problem is to not dump any material in rivers and not to plant cacti anywhere.
“Spreading takes place mostly due to the illegal dumping of unwanted material in rivers. Rather take it to a dumpsite where it can be covered with soil at least 1 meter thick,” he said.
He added that the process to release biological control agents is underway and that these agents are target specific and will only target the particular cactus species.
The agents Akwenye is referring to is a proposed plan by the Namibian Chamber of Environment to release three host-specific insect species to control infestations of these invasive cactus species. Voigts supports this move, saying, “Wherever there are tested and safe natural enemies available, they should be released into our environment as a matter of urgency to help bring down the speed of vegetation conversion.”
As South Africa and Australia experienced similar problems, Namibia can profit from their research.
But she warns, “Even when a cactus is already dying, it is likely to activate a lot of generative and vegetative propagation beforehand.”
So, even if a cactus is dead, it still has to be physically removed. Moreover, it will take years before an infested cactus will be killed by an insect infestation and in this time the cactus will still produce offspring and seeds.
“We should not rely on one single method, but activate all means simultaneously and as fast as possible,” she proposed.
The cacti are especially proliferate and have destroyed the vegetation in Zenobia Street and at Farm Windhoek around the Waldorf School. “The problem can no longer be handled by a few individuals and some supporters alone, and we cannot rely entirely on proposed insects.”
The cheapest and fastest way to get rid of cacti is to rake it out. “If we throw it into a City of Windhoek cactus skip, the municipality will remove it for us,” she says.
Workers employed through the Cactus Clean-up initiative get paid N$140 a day, which is paid from donations received.
If you would like to become involved or make a donation, send an email to [email protected]