Background to the project

Cowpea and bruchid

Cowpea is important in semi-arid areas:

  • Being a traditional crop, it is well adapted to semi-arid climates and can therefore withstand relative droughts and does not need as much inputs like fertiliser as other crops. In fact, as for all legumes, cultivating cowpea even enriches the soil in nitrogen.

  • As a source of non-animal protein. It is important for human consumption, because of the high protein content of its beans, in areas where meat is not available in sufficient quantities.

A cowpea field in northern Ghana

Cowpea and maturing pods

Cowpea on sale on Tamale market (Northern Ghana)

The importance of cowpea in Ghanaian food is illustrated by the many recipes used to prepare it. Two example available on the web are: Black-eye bean stew and Rice and Beans

In semi-arid areas, food produced during the rainy season has to be stored for the duration of the dry season which can last up to 7 or 8 months. Farmers have traditionally stored their foodstuff in granaries, in the household compound or nearby. The harvest is dried and stored, and over the dry season, the family will take out of the store what it needs to cook and sell on the market when it needs cash. Cowpea beans could then be consumed the whole year round, and financially it is worth storing it as the market price will rise with scarcity, over the dry season.

But the main pest of stored cowpea is the bruchid Callosobruchus maculatus which can damage severely stored grains

Cowpea damaged by bruchids

Adults cowpea bruchids (from A. P. Ouedraogo's Doctorate thesis, University of Tours)

The bruchid life cycle takes about 1 month, adults mate and lay eggs within 5 days of emergence, and each female can lay up to 100 eggs:

The damage caused by the bruchid can be very high, and the entire stock could be destroyed in a few months. Because of this risk, and because they need cash after the harvest season, farmers are reluctant to store their cowpea, and will sell it early after harvest, when its price is lowest. They will not benefit from the high prices attained later in the dry season, and will even have to purchase cowpea at that price because they have not got enough in their stores to feed their family.

This project had for objective to research methods of control against the bruchid, which would be effective, affordable and safe for small scale farmers in semi-arid areas, and would allow them to store cowpea during the dry season.

The geographical location

Most of the project work was undertaken in northern Ghana, in the Northern Region. The field work took place in Gushegu district, where cowpea is widely grown, and the project office was based at the Post Harvest Development Unit of the Ministry of Food and Agriculture, in Tamale.