Experts to Probe Acacia ‘Cancer’


By Moses Magadza


A team of top South African-based scientists is expected in Namibia “soon” to further investigate a cancerous outbreak threatening the Acacia karroo, one of sub-Saharan Africa’s most common trees.

Last year, The Southern Times reported that Namibian-based scientists had detected a cancerous outbreak among the trees and warned that the outbreak could decimate the tree and spell doom for Namibia’s burgeoning tourism industry, which is driven by tourists and trophy hunters who are drawn to the country by wild animals that largely feed on Acacia karroo and other similar species.

Acacia karroo is very widely distributed in Africa and is a prominent component of the savannah ecosystem.

It has very nutritious leaves and is also used for medicinal purposes, treating an array of health conditions that include sores, headaches, pneumonia, diarrhoea, gynaecological problems and eye inflammation.
Its sap is sweet and edible.

The bark can be used as a perfume, while its sap is also used as a softener in the tanning industry. When in flower, it attracts a lot of insects, notably bees that are crucial to the well being of the honey industry. In Namibia, the Ovaherero use the sap from its bark to flavour sour milk.

The disease under investigation causes pod malformation among Acacia karroo, inhibiting seed development and literally rendering the trees ‘barren’.

Now Professor Yolanda Roux, a plant pathologist and expert in forestry extension services in South Africa, will lead a group of other experts to Namibia to collect more samples and conduct a national survey to determine the nature and extent of the outbreak.

Plant Biologist, Dr Percy Chimwamurombe, who highlighted the outbreak and has since written an academic paper on this disease, has confirmed that the scientists would indeed come “before winter”. He was optimistic that they would confirm findings that he and others made last year.

“We expect them to arrive before May so that they can visualise the impact because trees will be green and it becomes easy to observe affected trees,” Chimwamurombe said.

When the outbreak was detected in January last year, Namibian scientists suspected that insects caused the infection but extensive studies have exonerated the insects.

“We hypothesised that these were insects or microbial infections. We have now ruled insects out as the cause. Based on Deoxyribonucleic Acid (DNA) tests and other analyses, we can now conclusively say that this is a fungal infection. The visiting scientists will do more sampling and give a second opinion, which we expect will be a confirmation of the identity of the disease-causing organism. They will conduct further tests and infection studies as well as monitor the development of symptoms over time, ideally two seasons,” he said.

The envisaged study will be thorough and has been made possible through funding from South Africa’s National Department of Science and Technology through the National Research Foundation funding mechanism.

Some of the researchers will be drawn from the prestigious Forestry and Agricultural Bio-Technology Institute, which is widely acknowledged as the “be all and end all” of research in commercial forests and indigenous trees in southern Africa.

Chimwamurombe said lack of human and financial resources was slowing down research by his team and ran short of telling New Era he was annoyed at feet-dragging over the matter by various stakeholders.

“We have written to various organisations and companies requesting funding to do more research, to no avail. It would appear that the wisdom inherent in the famous adage that a stitch in time saves nine is not generally appreciated,” he said.

Acacias constitute the highest percentage of tree flora in Namibia and most semi-arid parts of southern Africa. They form the bulk of the diet of browsers that include giraffe, kudu, springbok and large herbivores such as elephants, which have been known to draw tourists and trophy hunters. Goats and cattle browse on it. Fungal infections have wiped out important generations of plants elsewhere in the world. In 1840 a fungus triggered the well-documented Irish potato famine, while in the 1900s a fungus called Cryphonectria parasitica wiped out America’s chestnut plants. During biblical times another fungus, Phytophtora infestas, attacked barley in Israel, causing famine, which drove the Israelites off their land into Egypt.


Please enter your comment!
Please enter your name here