Got a bug problem with your beans? Just bag it.

More than 25 percent of unprotected cowpea is lost as a result of pest attacks during postharvest. However, these losses are being substantially stemmed, thanks to the Purdue Improved Cowpea Storage (PICS).

PICS aims to put half of all farm stored cowpea harvest in West and Central Africa in non-chemical, hermetic storage. Here's how: PICS works by sealing cowpeas in an airtight container. The airtight container within a couple of days kills all the adult insects and most of the larvae. The technology also keeps the remaining larvae dormant and unable to cause further damage. PICS was developed through collaboration between Purdue University's Faculty, students and researchers in North Cameroon in response to farmers, who had problems storing cowpeas and needed an effective storage method.

A PICS bag is composed of three layers: two inner layers of high density polyethylene and an outer layer of ordinary woven polypropylene. The inner bags protect the grain from insects. The bag was tested in the laboratory and in over 20 000 village tests in West and Central Africa. It has drawings illustrating sealing procedures to help illiterate farmers.

Jess Lowenberg-DeBoer, a Professor of Agricultural Economics and Director of the International Programs in Agriculture at Purdue University, said hermetic storage works effectively only when containers are completely filled. PICS bags have a 100kg capacity but if a farmer has 50 kg of cowpea to store, the bag can be tied lower down and this works just as well. Can it be reopened continuously?
"Yes it can, but the problem is that it introduces oxygen again," Lowen-DeBoer said. "We have found that once farmers re-open the bags, particularly if they are using cowpea for household use, it means the insects that are not killed will wake up and start trying to eat the cowpea. So it is better once sealed, to leave it sealed until the cowpea is taken out for sale."

Smaller containers, like plastic bags can be used to store cowpea for household use.

The PICS bags are available in 10 countries in West and Central Africa and are currently being manufactured in Senegal, Mali, Ghana and Nigeria. On average, the bags cost between $1.70 and $3 depending on local manufacturing costs.

"The bag makes a difference. For example, if a bag of cowpea is worth the equivalent of $50 at harvest and $150 six months later and you spend $3 on the bag, there is still a tremendous possibility for gaining."

Purdue University is working with IITA in Nigeria to promote the adoption of the cowpea storage technology.

- Busani Bafana