Killer weed invades farms, grazing lands and national parks

[Daily Nation 26 Jan 2011][Jacob Ng'etich]--Just like hyacinth in the early 1990s, and Striga weed a decade later, the Parthenium hysterophorusa weed which “sneaked” into the country a few years ago threatens to hurt the flora and fauna if its spread is not curtailed. There are fears that unless the government acts immediately, the Parthenium hysterophorusa, a noxious weed now spreading alarmingly in several parts of the country, will reduce agricultural and livestock productivity, and seriously affect wildlife. At great risk from the weed also known as Santa Maria feverfew, are farmlands, grazing fields, national parks and game reserves. The weed multiplies and spreads fast, while inhibiting other underground growth. According to the director of Agriculture, Mr Humphrey Mwangi, the weed is alarmingly sprouting in several places within the short period it has been noted.

Parthenium hysterophorusa weed. Photo/LIZ MUTHONI

Mr Mwangi said of the weed which came into the limelight early last year: “The weed was designated by agricultural authorities in the Ministry of Agriculture as plants that are injurious to agricultural crops because they grow aggressively, multiply quickly and adversely affect desirable plants’ qualities.”

The director noted that the weed had limited distribution but had the potential of becoming more widespread and cause impact on agriculture as well as human health and environment. The potential adverse impact of the weed exceeded far beyond the cost of implementing the control measures, he said. Ms Triza Karanja a pathology and weeds officer at the ministry said the impact on the noxious weed was reduction in agricultural yields and grain weight. It also acts as alternate host to crop pests. According to Ms Karanja, there was also an enormous impact on animal husbandry where the Parthenium weed could reduce pasture carrying capacity by up to 90 per cent.

Other serious dangers have been raised over the growth of the weed in game reserves and national parks. Maasai Mara ecosystem in Kenya which hosts the largest wildlife migration known to man has not been spared the attack by the noxious weed. According to researchers, the weed originally from Central America has been found growing along parts of the Mara river and along some dirt tracks in Maasai Mara National Reserve. Dr Arne Witt, an invasive species coordinator at the Centre for Agriculture and Bio-Sciences International (CABI) Africa said although the weed may look benign to most people, it probably posed one of the most serious threats to the ecosystem.

Mr Joseph Ng’etich, head of Plant Protection Services Division, said the weed could also reduce yields of crops, such as sorghum, by up to 97 per cent. Mr Ng’etich said the noxious weed was also toxic, which means that animals would not eat it unless they are starving or stressed, with fatal consequences. Dr Witt also explained that many people who came into direct contact with the plant could develop severe skin allergies (dermatitis) and pollen production by the plant can result in respiratory problems. The implications for wildlife conservation in the Maasai Mara ecosystem are potentially serious; the movements of thousands of grazing animals searching for pastures, meant that the grasslands were often highly disturbed, making it easier for parthenium to invade.

“Unless action is taken immediately to eradicate known infestations in the Maasai Mara it is not unrealistic to expect a drastic reduction in wildlife population in the long term as the parthenium population rapidly expands as an invading species,” says Geoffrey Howard, IUCN’s global invasive species programme coordinator.

“It is therefore possible for a little green plant to transform one of the greatest spectacles on earth.” Early last year, former Agriculture minister William Ruto gazetted Parthenium hysterephorus as a noxious weed.

In a gazette notice of 13th April, 2010 under The Suppression of noxious weeds Act he declared: “Because of the threat that this weed poses to biodiversity, agriculture and human health, the government of Kenya has declared it a noxious weed under the Suppression of Noxious Weeds Act.”

The Parthenium hysterophorus weed has also been declared a noxious weed in other countries like America and Australia due to its vigorous competitive growth and also its intense dermatitis reaction in many people. Parthenium produces large numbers of light seed in a short time which is easily distributed by wind, passing vehicles, machinery and water. Dr Witt exuded optimism that the invasion could be stopped if the government and other institutions were committed to managing invasive species in Kenya.

Wreaked havoc

In the past, different types of invasive weeds have wreaked havoc and affected human lives in different parts of the country and in the region. Hyacinth menace still exists two decades after it was reported in the country in the early 1990s. In 2008, the prevalence of Striga weed was reported in western Kenya and parts of eastern Uganda heralding a crisis due to its ability to greatly affect the production of food. But according to the scientists, Parthenium is the most worrying.

Source