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Famine weed (Parthenium hysterophorus) became well-established in South Africa in the 1980s after cyclone Demonia and is sometimes referred to as Demonia weed. In recent years, it has spread rapidly across KwaZulu–Natal, Mpumalanga and North-west provinces. It has the potential to infest frost-free sites throughout the summer rainfall zone.

Famine weed can generate up to 25 000 viable seeds per adult plant which can mature to the flowering stage in four weeks. This makes it a very dangerous invasive weed, especially in disturbed environments where it can rapidly establish and proliferate.

The name famine weed comes from the fact that it can have severe impacts on agriculture. In India, it caused yield decline of up to 40% in certain crops. In Ethiopia, sorghum yield was reduced by between 40% and 90% in areas where it was not controlled and in Queensland (Australia), it is estimated that rangeland infestation cost the livestock industry $168 million a year. The weed produces allopathic chemicals which inhibit the growth of other plants allowing it to spread rapidly. It is also toxic to livestock and can cause human health problems such as asthma, bronchitis and skin problems.

The plants’ seeds can easily be carried in mud caked on vehicles and are often spread over long distances in this way. It is important to identify new infestation early and to eradicate these plants

immediately before they get a foothold. Roads, railway lines, power lines, riparian areas and similar corridors often serve as pathways along which the weed spreads. These areas should be checked on a regular basis.

The best way to control the weed is to ensure good land management practices. Overgrazing results in bare soil and allows the weed to invade. Cultivated lands must be kept weed-free and plantations need regular inspection. Plants can be pulled out from the roots before flowering or sprayed using a registered chemical. Workers must wear protective gloves, clothing and a facemask at all times. Picloram 240g at a 0.5 concentration has proved to be effective as a foliar spray. If the weed is present on a farm, it is essential to do an initial spray with a minimum of two follow-up operations a year. This will ensure that plants to not have a chance to set new seed.

Biological control is going to be an essential part of the war on famine weed. Two leaf rust fungi, a stem-boring weevil and a leaf feeding beetle have already been released. Ongoing research by the Agricultural Research Council will result in further control agents being released in the future. However, it is essential that landowners improve their management practices to lower the risk of invasion by this plant and reduce current infestations on their land.

(Reference: Farmers’ Weekly – December 2013 – WESSA Training brochure)

FAMINE WEEDA threat to food security, biodiversity & health

Craig Norris, NCT’s Forest Technology Services Manager

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The plant is a prolific flowerer producing up to 25 000 viable seeds

A young plant growing in disturbed soil

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Roads often act as pathways for famine weed to spread along