Insects to control infestation

The end of invasive species in sight

19 November 2018 | Environment

The Namibian Chamber of Environment is proposing the biological control of alien invasive cacti in the capital.

Yolanda Nel - Large areas of the capital have already been infested with three specific cactus species that are preventing other plants from growing.

For this reason, the Namibian Chamber of Environment, together with the Botanical Society of Namibia and the Rhodes University Centre for Biological Control in South Africa, are working on introducing biological control against these plants.

A public notice that appeared in various media, stated that the project entails releasing three host-specific insect species to control infestations of these specific invasive cacti species. The problematic cacti species are the Imbricated, Pest Pear and Snake cacti – all likely to spread and invade other parts of the country if control measures are not implemented.

These species are such a problem, that “their spines can damage and kill local wildlife and make the areas impenetrable for people”.

Although the clearing of cacti can be done manually, it is expensive and time-consuming and no people can ever get ahead of new infestations that constantly appear in new locations. Control using poisons is dangerous due to the pollution risk and it also expensive. Also, these methods can only react to the presence of new plants once they are detected.

“Introducing species-specific natural enemies of each cactus species, will effectively control their abundance at very low levels,” according to the document.

The insects that can control the invasive cactus plants will be imported from South Africa, where they have been proven to be very effective against the targeted cacti. Two of the agents are cochineal insects, which appear as white waxy blotches, like cotton wool on the cactus leaves. The other is a mealy bug which forms lumps in the cactus plants and prevents it from propagating.

These species feed on the plants by sucking the sap, which kills or sterilises the plant.

Biological control

Biological control is considered to be the most effective and environmentally friendly method of controlling alien invasive cacti in Southern Africa and Australia, where very problematic cacti have been controlled for more than 100 years. All the agents are host specific, only feeding on the target weed and a few other closely related cactus species that are also alien to Africa.

No indigenous plants can be harmed by the release of these agents.

Since there are no active biological control practitioners in the country, this project will include students who will participate in the trial by mapping the invasive alien species in the country and monitoring the outcomes.

The Namibia University of Science and Technology (NUST) has committed to undertake long-term studies ­in collaboration with this programme.

“The release of these agents in Windhoek will be beneficial as it would result in the sustainable, long-term control of these damaging invasive species for the protection of ­agricultural productivity and indigenous biodiversity,” the document read.


The cactus mealy bug can damage other alien columnar cactus plants, and a small amount of spread to garden plants may occur.

However, the dispersal of the mealy bug is likely only over short distances, not more than a few hundred metres.

Since alien cacti should not be

encouraged at all, nurseries are

being asked to rather sell and promote indigenous succulents which are not invasive and do not cause problems for local wildlife.

“Any damage to local garden cacti should be considered a small price to pay for the huge

benefit that the bio-control will have on invasive cacti.”

For comments or concerns about the project, contact [email protected] or [email protected] by Monday 26 November.

Similar News


Seeing the unseen

2 days ago - 24 March 2019 | Environment

Bank Windhoek, in conjunction with the University of Namibia (Unam) and Netherland’s Radboud University (RU) Nijmegen, host a scientific event titled ‘Building the Namibian Africa...

From cooking oil to biofuel

2 weeks ago - 10 March 2019 | Environment

Windhoek • Yolanda NelA bottle of cooking oil is heated up in the deep fryer to make the perfect, golden chicken nuggets. Once the oil...

How the Moringa can purify water

2 weeks ago - 10 March 2019 | Environment

Next Thursday (14 March), the National Commission on Research, Science & Technology (NCRST) hosts a public lecture presented by Prof Habauka Kwaambwa on the evaluation...

Where to with the animals?

2 weeks ago - 10 March 2019 | Environment

Windhoek • Nina Cerezo Following the recent culling of hyenas to save the Wild Horses of the Garub, environment minister Pohamba Shifeta repeatedly referred to...

Climate change slows aquaculture

3 weeks ago - 03 March 2019 | Environment

Lüderitz • Ewin LeuschnerA workshop titled Enhancing Climate Change Resilience in the Benguela Current Fisheries System was ­held in Lüderitz recently, where experts discussed the...

Blue economy faces myriad challenges

3 weeks ago - 03 March 2019 | Environment

Windhoek • Jana-Mari Smith “The work on Namibia's blue economy is on-going, yet little information on the status thereof exists,” says Institute for Public Policy...

Way too much waste in Africa

1 month - 24 February 2019 | Environment

Windhoek • Yolanda Nel Current trends indicate that Africa's waste generation is expected to reach more than 240 million tonnes per year by 2025...

Conservation snapshot

1 month - 17 February 2019 | Environment

On Tuesday (19 February), Peter Bridgeford launches the book Conservation Pioneers in Namibia and stories by Game Rangers at the Scientific Society.This book of personal...

Elke bietjie help

1 month - 10 February 2019 | Environment

Yolanda Nel Daar is niks so lekker soos ’n heerlike espresso nie – veral nie as daardie varsgemaalde goue stroop deur ’n masjien loop nie.En...

Insects heading to Windhoek soon

1 month - 04 February 2019 | Environment

Yolanda Nel With large areas of the capital already infested by three invasive cactus species, various avenues are being pursued to prevent further spread...

Latest News

Beach volleyball action at the...

1 day - 25 March 2019 | Sports

Social division action from the first day of the Namibian Volley Ball Federation (NVB) organised 2019 Bank Windhoek Swakopmund Beach Volleyball tournament at the Mole....

Schools compete at desert sport...

1 day - 25 March 2019 | Sports

The sixth annual Buco Desert Sport Festival took place from 19 to 23 March at the Walvis Bay Private High School sports field. This year...


1 day - 25 March 2019 | Sports

Thirty eight archers are competing at the first ever outdoor target archery competition in Swakopmund. The competition which is taking place over two days...

The soldiers among us

1 day - 25 March 2019 | Sports

Windhoek • Yolanda NelHundreds of athletes and rookies joined in the fun during the Toyota Warrior Race that took place at Heja Lodge yesterday. Armin...

Two in a row for...

1 day - 25 March 2019 | Sports

Swakopmund • Adolf KaureThe second edition of the Sanlam Coastal Marathon took place in Swakopmund.Mynhard Kauanivi won the men's 42.2 km marathon for the second...

Fundraising for strays

2 days ago - 24 March 2019 | Society

Windhoek • Yolanda NelGiven that a single pair of dogs and their offspring are able to produce more than 11 000 puppies a year and...

Kom bak en brou saam

2 days ago - 24 March 2019 | Society

Windhoek • Yolanda NelWou jy nog altyd ook koekies mooi versier, maar die taak lyk glad nie bereikbaar nie?Dan is hierdie ’n geleentheid wat jy...

Little foot entertains

2 days ago - 24 March 2019 | Business

A newly erected chameleon structure is entertaining children at the Grove Mall of Namibia.Since chameleons are well-known for their adaptations to survive the brutal deserts,...

A better future for the...

2 days ago - 24 March 2019 | Social Issues

Windhoek • Yolanda NelStatistics on how many Namibian children are at risk, is dire. As a result, a group of people decided that something needs...

Load More