New drive to save African crops from parasitic weeds

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Scientists in Nigeria and Kenya have started a major war against parasitic weeds that cost small scale farmers in sub-Saharan Africa $1.2bn in harvests every year, aggravating food deficits

An initiative coordinated by the Nigeria-based International Institute of Tropical Agriculture (IITA), will introduce new methods for fighting Striga, or witchweed, and Alectra. Known as the “violet vampire” because of its bright purple colour, Striga attaches itself to the roots of plants like maize and cow peas and sucks out nutrients, reducing yields and destroying entire harvests.

Witchweed primarily affects smallholder farmers who cannot afford herbicides for fighting the parasitic plant. The most widespread Striga species is estimated to have infested up to four million hectares of land under maize in sub-Saharan Africa, causing yield losses of up to 80 per cent. According to researchers at IITA, this represents up to $1.2bn in losses for farmers and affects about 100mn people in the region.

The parasitic weeds have spread widely in Africa because of their seeds feed on substances released by the roots of crop plants to germinate faster. The weeds also produce seeds that can remain dormant in soils for decades.


“Push-pull” technology

The Bill and Melinda Gates Foundation has given IITA $6.75mn as part of a campaign to help 200,000 maize farmers and 50,000 cow pea farmers raise yields by 50 per cent and 100 per cent, respectively.

The four-year project aim to improve and expand access to methods of Striga control including using a “push-pull” technology that involves intercropping with legumes that inhibit the germination of Striga, using herbicide-coated seeds and deploying bio-control of Striga.

Scientists expect that the integrated witchweed control interventions will generate an estimated $8.6mn worth of additional grain (maize and legumes) increasing incomes, improving nutrition and reducing poverty.

“The project aims to raise farmers’ awareness of the technologies, and supporting community-based organisations with technical assistance,” said Prasanna Boddupalli, director of the Global Maize Programme based in Nairobi. About 80 per cent of the population in sub-Saharan Africa depends on agriculture for food, income, and employment.

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