10 May 2005 

How companion planting is helping over 3000 African farmers

Parasitic witchweed, Striga species

Scientists from Rothamsted Research (1) will be exhibiting at the Chelsea Flower Show (2) in order to explain the science behind companion planting. Their work is helping to support new farming systems, which are transforming the livelihoods of over 3000 resource poor farmers in Kenya, Uganda and Tanzania.

Companion planting (3) is a traditional way for gardeners to protect their plants. However, in many cases, it is not known why such partnerships work. Scientists, led by Professor John Pickett, are investigating these interactions and their discoveries are helping to enhance the effectiveness of such systems for the protection of crops on a field scale, particularly in developing countries.

Maize and sorghum are the main food crops in sub-Saharan Africa. The major constraints to the production of these crops are stem borer moths and parasitic witchweeds (Striga species). A "Push-pull" companion-planting strategy has been developed (4) for the control of these pests. Intercrop plants, such as silverleaf and greenleaf (Desmodium species), planted between the crop rows, emit an odour which repels stem borers from the crop (the "push"). At the same time, a trap crop, such as Napier grass, planted around the crop, attracts the stem borers away from the crop (the "pull"). Desmodium species also produce root exudates that inhibit the growth of witchweed.

Kenyan smallholders Lawrence and Joseph Odek have seen stem borers and witchweed devastate their yields for as long as they can remember, often forcing them to turn to charities for food. After three years with the push-pull system, their maize yields have increased from five 90kg bags to 35 bags. They now have food security and have been able to sell some maize to pay for their childrens' school fees and re-roof their house.

Scientists at Rothamsted Research in partnership with scientists at ICIPE in Kenya have determined the nature of the ecological interactions behind this, and other similar intercropping systems. Only by identifying the chemical signals involved can such systems be fully understood and sustained.

The exhibit at Chelsea will show companion planting at work in both an English vegetable garden and an African smallholding. An African crop advisor (George Genga) and an African small holder (Mary Rabillo) will be on the stand at selected times for interviews and photo-opportunities. Scientists are available for interview on request.

Contact

Press Office Tel: 01582 763133 ext 2260. Angela Cornford
Tel: 01582 763133 ext 2320
Email: angela.cornford@bbsrc.ac.uk

Notes for editors

1. Rothamsted Research (www.rothamsted.ac.uk) is one of the largest agricultural research institutes in the country and is sponsored by the BBSRC.
2. The RHS Chelsea Flower Show 24-28th May (24th & 25th RHS member days) www.rhs.org.uk
3. Companion planting is the planting of certain combinations of species close together for mutual benefit.
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4. The approach was developed by the International Centre of Insect Physiology (ICIPE, www.icipe.org; www.push-pull.net), Rothamsted Research, the Kenya Agricultural Research Institute (KARI) and the Kenya Ministry of Agriculture.
5. The research was funded by the Gatsby Charitable Foundation, the Rockefeller Foundation and the Department for International Development.

1. For further information, please contact the Rothamsted Research Press Office on 01582 763133 ext 2260 or email Adélia de Paula (adelia.depaula@bbsrc.ac.uk)
2. Rothamsted Research is based in Hertfordshire and is one of the oldest and largest agricultural research institutes in the country. The Applied Crop Science department is based at Broom's Barn, Higham, Bury St. Edmunds. North Wyke Research is located near Okehampton, Devon.