SA famine threat from toxic alien
‘Frankenstein plant’ fast taking over arable land
ALMOST reluctantly, Riaan Malan (not his real name) bends down in a field filled with pretty white flowers. He tears one off at the stem. “Do you know that each of these plants can make as many as 25 000 seeds? Jis, this plant is very bad.”
Malan, an ag ricultural adviser who does not want to be named because he works closely with the government, is right to be worried about this dangerous yet inconspicuous-looking plant that resembles a daisy.
The Department of Environmental Affairs has dubbed it a “Frankenstein plant”, describing it as an “unwanted and relentless gatecrasher” in South Africa.
And here in Brits, North West province, Parthenium hysterophorus, more commonly known as famine weed, is “spreading like wildfire”.
In the past five years, Malan has watched how the plant, which takes only a month to germinate, has crept into the town, spreading on to the roadsides, farms and waterways.
Malan surveys the field, which two years ago looked nothing like this. “The last time I was here, there were just a few plants. Now, look at how it’s taken over this valuable grazing land.”
Later, as he circles Brits in his bakkie to illustrate the spread of famine weed, Malan’s hands start to itch. The weed secretes a highly toxic substance called parthenin, which can cause severe allergic reactions including dermatitis, hay fever and asthma. This can contaminate milk and the meat of the animals that eat it.
Like the dreaded fall armyworm that threatens to wreak havoc on maize crops in southern Africa, the pesky famine weed is on the march, too. “We have armyworm in Brits, but the farmers are dealing with it. You can see it’s impact, but the famine weed, in two to three years, it explodes everywhere.
“In Nigeria it’s so bad they say when you have famine weed, you must leave your farm.”
That’s what concerns Lesley Henderson, a weed scientist at the Agricultural Research Council’s Plant Protection Research Institute.
“South Africa’s worst drought in more than 30 years led to vast tracts of denuded land in large parts of the country,” she writes in its newsletter. “Recent good rains in northern Kwa-Zulu Natal and Mpumalanga low-veld has seen the massive resurgence of the rapidly-growing, invasive alien species, which out-competes indigenous plants and crops and causes allergic reactions in humans and animals. Left uncontrolled it can lead to famine, hence the name.”
Famine weed is spreading to areas “that were lightly invaded are now densely invaded and some areas which were critical to keep clean have now been invaded”.
She salutes efforts by landowners and authorities to curb its spread, using biological control agents – natural enemies like weevils and rust fungi to eradicate the species.
But a national strategy drawn up last year and accepted by the Department of Environmental Affairs with a refined implementation plan, has still been unable to control the weed.
The department did not respond but Bomikazi Molapo, of the Department of Agriculture, Forestry and Fisheries, pointed out that under the steering committee co-ordinated by the department, the Agricultural Research Council (ARC) has released biological control agents in South Africa and in East Africa since 2003.
“It’s incorrect the government is not doing anything. Certainly, there’s action being undertaken with co-operation and technical support of the ARC,” said Molapo.
The 2016 plan, An Approach to the Development of a National Strategy for Controlling Invasive Alien Plant species: the Case of Parthenium hysterophorus in South Africa, was drawn up by a team of researchers from the SA National Biodiversity Institute, the ARC and the Centre for Invasion Biology at Stellenbosch University.
They warn how the spread of the species could have “serious consequences for the agricultural economy, human health and biodiversity coupled with its recent rapid expansion”.
Growing infestations “will almost undoubtedly have serious consequences for rural economies and the health of people in invaded areas”.
The researchers cite a 2007 study that found if famine weed was allowed to spread beyond control, returns to small-scale far mers could decline by as much as 41%.
Native to tropical America, famine weed has become invasive in more than 30 countries, thrives in disturbed areas and is easily dispersed by water, animals, vehicles, tools and machinery. The plant’s seed banks can persist in soil for up to six years.
The abundance of invasive alien plants is recorded within quarter degree grid cells of 25km x 25km. In 1980, three cells of famine weed were found; by 2014, this had grown to 76.
“It’s not clear whether the goals of the strategy are achievable because implementation will face many challenges arising from ecological features of the target plant, social and cultural practices that will influence management, inadequate levels of funding and multiple political considerations,” states the strategy.
After it published amended re gulations on Alien and Invasive Species in 2014, the department described famine weed as having “the potential to invade all but the driest parts of South Africa, and most of Africa.
“Fields of famine weed will wreak economic, ecological and health havoc. Neither South Africa’s stock nor game species can survive in these invaded areas.”