'Noxious' weed spreads across Africa towards Kenya's savannahs

Laurence Caramel in the Guardian (UK): No one knows how feverfew reached south-west Kenya. But the threat it poses led to a recent alert from the International Union for Conservation of Nature (ICUN) issued to the international scientific community: "The Serengeti – Masai Mara ecosystem in Africa, which hosts the largest wildlife migration known to man, is under attack from a noxious weed."

Masai Mara, which runs along the border with Tanzania, is home to Africa's largest herbivore population. At the start of the annual rainy season, millions of wildebeest, gazelles, zebras and giraffes leave the Tanzanian savannah for the plains of Kenya in search of fresh pastures. A few months later, towards December, they circle back completing a round trip of several hundred kilometres. But what would happen if the weed, originally from Central America, colonised this wildlife sanctuary?

Parthenium hysterophorus, commonly known as Santa Maria feverfew or whitetop weed, is one of the world's 10 most dangerous weeds. It can grow two metres tall. Until now it has only been seen on tracks crossing the wildlife reserve and on the shores of the river Mara, which flows through the Serengeti.

"It is very hard to say how long it will take for the invasion to spread to the whole park, because that depends on many factors, in particular climatic conditions," says Arne Witt, Invasive Species Co-ordinator at the Centre for Agricultural Bioscience International (Cabi). "But the example of neighbouring Uganda shows that it may be very quick. The plant was first spotted three years ago and it is now seen all over the country. Bearing in mind that it can grow from seed to maturity in four to six weeks and can produce 10,000 to 25,000 seeds, contamination can happen very quickly," Witt adds....

Parthenium, also called gajar ghas, is a genus of flowering plants in the aster family, Asteraceae. It is also called bitterweed, carrot-grass, false ragweed, feverfew, parthenium-weed, ragweed parthenium, Santa Maria feverfew, whitetop, coentro-do-mato, losna-branca, cicutilla. It is biggest problem in cultivation in India. Photographed at Howrah, India by Biswarup Ganguly,
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