A HIGHLY invasive plant that goes by the sinister common name of ‘famine weed’ is starting to make its deadly presence felt in KwaZulu-Natal.
At the recent South Coast Conservation Forum annual general meeting, invasive weed expert Peter Charlton warned local conservationists about this threat. While this Category 1 invader, Parthenium hysterophorus, had not yet been spotted on the South Coast, it had already invaded large areas of Swaziland and adjoining areas in northern KwaZulu-Natal.
Its common name was most descriptive as it caused devastating disruptions in agricultural areas and had indeed triggered famines in some countries, he said. It also posed a threat to wildlife, tourism and even to people.
Mr Charlton explained that it posed a serious health risk, causing extreme allergic reactions in both animals and people. Animals grazing where the weed was growing suffered from severe lesions around their mouths and on their limbs. Humans also developed sores and blisters if they touched any part of the plant and workers eradicating it had to wear protective gear.It also triggered asthma attacks in humans, even those who had never suffered from asthma before coming into contact with the plant.
When it invaded agricultural land it rendered it useless for grazing. Invasions along river banks by the poisonous weed also prevented domestic and wild animals from drinking from the river, he said.
“In some areas of norther KwaZulu-Natal about 70 percent of farmlands have been invaded,” he said.
This rapidly growing plant appeared to be spreading along transport routes, as vehicles driving through a patch of the weeds would inadvertedly disperse the seeds. In Australia, where it had become a major problem, authorities had been forced to set up roadblocks and spray the exterior of all passing vehicles to prevent the spread of the plant. Environmental agencies might well be forced to set up similar programmes here, he said.
The Durban Early Detection and Rapid Response Unit, set up by eThekwini Municipality, the Natural Resources Management Programmes and the South African National Biodiversity Institute’s Invasive Species Programme, has also sounded the alarm.
According to the unit, famine weed was an annual herb that came from North America. The weed posed a major health hazard as it was a nerve depressant. It also produced allergenic dermatitis and asthma in humans. It was spread by seeds that could be viable for many years and was browsed by stock. Cattle that had consumed the Parthenium weed were not fit for human consumption and their milk became toxic.
Parthenium weed was typically kept under control by using mechanical and chemical removal. Spraying with a selective herbicide so that other species were not killed was highly recommended. Treated areas should be closely monitored for up to seven years so that outbreaks did not occur, the unit advised.
The good news was that famine weed had already been subjected to biological control in Australia where nine insect agents and two rust fungi had been successfully established. The unit hoped that cooperation with Australian researchers would help South African authorities to ‘fast track’ the control of this menace in South Africa.
Mr Charlton said authorities were already taking the problem seriously. Some R3-million had been allocated to control the weed in the area next to the Swaziland border. Ezemvelo KZN Wildlife had also requested R10-million to be used to eradicate the weed from its reserves, he said.
