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Cowpea: bagging the bugs

Cowpeas are an important legume in the Sahelian tropical zones of Africa (© T. Abdoulaye/IITA)
Cowpeas are an important legume in the Sahelian tropical zones of Africa
© T. Abdoulaye/IITA

A simple triple bag technology is helping smallholder farmers in Africa, who produce 70 per cent of the global production of cowpeas, to save more than 25 per cent of the crop currently lost each year to pests after harvesting. An important legume in the Sahelian tropical zones of Africa, cowpea (Vigna unguiculata L. Walp) is an important protein source to the many lacking access to animal protein; the seeds contain upto 25 per cent protein and the leaves are a valuable fodder for livestock.

Cowpea is seen as being increasingly important in reducing malnutrition, and a recent four-year study by Miriam Otoo at the Agricultural Economics Department at Purdue University showed that there is significant value addition when cowpea is made into the deep-fried cakes known as akara and sold by women as street food in Niger and Ghana. Cowpeas could also prove a solution for farmers adapting to climate change because of its resilience in dry, hot conditions. But according to the International Institute of Tropical Agriculture (IITA), pests - particularly the Maruca vitrata pod borer - currently cause losses of up to US$300 million for smallholder farmers in Africa.

The triple bag

A technology developed by Purdue University in collaboration with African researchers, known as Purdue Improved Cowpea Storage (PICS), is literally 'bagging' the problem of cowpea bugs by using non-chemical, hermetic storage. PICS has been introduced in West, Central and East Africa where farmers are exposed to harmful chemicals while protecting their cowpea grains against insects. In Nigeria, Africa's major producer with 1.5 million tons annually, net gains from not using pesticides have been estimated to be in the region of US$500 million.

Hermetic storage works effectively when the bags are filled completely (© T. Abdoulaye/IITA)
Hermetic storage works effectively when the bags are filled completely
© T. Abdoulaye/IITA

Jess Lowenberg-DeBoer, a Professor of agricultural economics and director of the international programs in agriculture at Purdue University, explains that PICS works by sealing cowpeas in an airtight container, which kills all the adult insects and most of the larvae within days. At the same time the triple bags keep the remaining larvae dormant and unable to damage the seeds. "A PICS bag is composed of three layers: two inner layers of high density polyethylene and an outer layer of ordinary woven polypropylene," explains Lowenberg-DeBoer. "The inner bags protect the grain from insects, the outer bag takes the knocks and scuffs and gives durability." The PICS bags have been subjected to tests in the laboratory and at over 20,000 villages in West and Central Africa.

Hermetic storage works effectively when the bags are filled completely. They have a capacity of 100 kg but, if a farmer has only 50 kg of cowpea to store, the bag can be tied and sealed lower down. Then, the bag should be opened only when the cowpeas are ready for sale or consumption. Lowenberg-DeBoer says farmers can use a triple-bag for several years and research has shown that many of the bags have been used for four years where farmers are careful and do not open them between times. Available in ten countries in West and Central Africa, the PICS bags are manufactured in Senegal, Mali, Ghana and Nigeria costing between US$1.70 and US$3.0 depending on local production costs.

Careful sealing the key

Sealing cowpeas in an airtight container kills all the adult insects and most of the larvae within days (© T. Abdoulaye/IITA)
Sealing cowpeas in an airtight container kills all the adult insects and most of the larvae within days
© T. Abdoulaye/IITA

Sealing the bag properly is critical for the PICs technology to work effectively but the technique is difficult to explain orally. Where farmers are illiterate, drawings are used to illustrate the sealing procedures, and Purdue has also turned to mobile phone technology to help farmers get it right first time. Working with its partners in World Vision and INRAN, Purdue has developed a short video demonstrating the sealing procedure, which can be called up on mobile phones. This has been a hit with many West African farmers who have passed the videos to each other using bluetooth when they meet in the markets. When tested in Niger, the video was given to extension workers and within a month it had spread to hundreds of people who saw the cell phone video and used the information.

Greater awareness

Use of triple bags for other crops is being tested. Says Lowenberg-DeBoer, "There is some indication that they work well for some but we are just starting research to examine that systematically." The two problems are insects that can bite through the bags and high humidity in countries where moisture content must be reduced before storage.

IITA has been collaborating with Purdue University and other partners in the development and testing of this technology in Africa. The focus is to make this technology available to smallholder farmers in West and Central African countries (Nigeria, Benin, Togo and Cameroon) because it is expected that better storability would increase farmers' adoption of improved cowpea varieties in the region. Surveys in northern Nigeria show that up to 64 per cent of farmers who attended PICS demonstrations are buying and using the bags despite the US$2 price tag in Nigeria.

Written by: Busani Bafana

Date published: December 2010


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PICS technology is simple and adaptable. Its importance so g... (posted by: Sule Sale)


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