Applying Research with Extension: 22 years of Strengthening Cowpea Storage in Africa

Joan Fulton¹, Larry L. Murdock², Bokar Moussa³,

Lee Stanish4, Kira Everhart-Valentin5, James Lowenberg-DeBoer6

The most economically-important indigenous African grain legume is cowpea, Vigna

unguiculata, related to common beans and chickpeas. Cowpea is one of the few crops that can

grow well in the harsh conditions in the semi-arid areas of West and Central Africa, making it an

important cash crop for small-scale farmers. In the 1990s it was planted on an average of 8

million hectares in West and Central Africa annually and on average produced 2.65 million

metric tons of grain (Langyintuo, et al., 2003). As a legume, cowpea is an important source of

protein for the entire population, both rural and urban. This nutritious food is prepared in a

variety of dishes, some of which are made at home, and others that are purchased on the street

either for immediate consumption or to take home for family meals (Ibro, Fulton, Lowenberg-

DeBoer, Moussa, & Otoo, 2007). Cowpea can also provide a relatively inexpensive source of

animal feed, its fodder is fed to cattle.

According to official statistics, during the 1990s nearly 300,000 metric tons of cowpeas were

traded in West Africa alone and marketed by an estimated 3.4 million households.

The Triple bagging method serves as the basic concept behind the most recent cowpea storage

program. Current efforts by Purdue University research and extension specialists, its African

partners and the Bill and Melinda Gates Foundation have combined in an $11.4 million extension

project launched in 2007.

Drum storage

Originally developed by Dr. Dogo Seck and others, drum storage is a version of hermetic (i.e. oxygen deprivation)

storage and involves storing the cowpea grain in a 60-liter metal drum. The drum is filled and sealed in an airtight manner.

Filled drums were shown to allow minimal losses to cowpea storage in a 6-month time period. However, good quality

metal drums can be cost prohibitive and/or unavailable in various parts of Africa.

Ash storage

Ash storage has also been a common traditional technique used to

fight post-harvest insects. It involves the mixing of cowpea grain with

sieved ash from cooking fires prior to storage. However, as traditionally

used, the amount of ash and how it was mixed with the grain varied

greatly from farmer-to-farmer. Therefore, research of this technique

was conducted at Purdue, and it was concluded that proportions of three

volumes or more of cooking ash spread on four volumes of cowpeas was

the minimum required to suppress the development of a weevil

infestation. Ash storage works well for small quantities of cowpea.

Solar disinfestations

Originating in the customary practice of spreading cowpeas out in the

hot sun to dry, solar disinfestations has been used by both farmers and

researchers to protect cowpeas. The weevil has a thermal death point of

57° C (Murdock and Shade, 1991). In solar disinfestations, the natural

heat of the sun is collected in man-made prototype heaters - such as the

one developed at Purdue involving black plastic sheeting - are employed

to raise the temperature of the grain to the thermal death point necessary

to kill all stages of the cowpea weevil. Farmers comment on the extra

labor required for solar disinfestations, compared to hermetic storage.

Triple bagging

Twenty-two years of research and extension work by Dr. Larry Murdock , other Purdue University scientists and

partners in Cameroon led to an extremely simple storage method – the triple bag system. Similar to drum storage, triple

bagging is version of hermetic storage. By sealing the cowpeas in a plastic bag and then sealing that bag within two

additional bags, the respiration of the feeding and growing weevils raise level of carbon dioxide in the bag while utilizing

the oxygen. Ceasing to feed, grow, and reproduce in this environment, the weevil population remains small and inactive

and so do not damage the grain. On-farm tests as a part of the Purdue/Cameroon Bean/Cowpea CRSP validated the

effectiveness of this technology, and additional research by the Purdue team led to the recommendation of a triple bagging

system in lieu of single or double bags. Triple-bagging of the cowpeas, using heavy-grade plastic bags, proved to be a cost

effective storage method that could be adapted by farmers with varying amounts of cowpea to store.

Ibro, G., Fulton, J., Lowenberg-DeBoer, J., Moussa, B., & Otoo, M. (2007). Niébé: Importance au Niger. Factsheet

produced as part of the USAID Bean/Cowpea Collaborative Research Support Program (CRSP).

Langyintuo, A., J. Lowenberg-DeBoer, M. Faye, D. Lambert, G. Ibro, B. Moussa, A. Kergna, S. Kushwaha & G.

Ntoukam. (2003). Cowpea Supply and Demand in West Africa. Field Crops Research. 82, 215-231.

Moussa, B. 2006. Economic Impact Assessment of Cowpea Storage Technologies in West and Central Africa.

Master’s thesis, August 2006. Purdue University, West Lafayette Indiana.

Murdock, L.L., Shade, R.E., 1991. Eradication of cowpea weevil (Coleoptera: Bruchidae) in cowpeas by solar

heating. Am. Entomol. 37, 228–231.

The Improved Cowpea Project (PICS) aims to extend the technology of the triple bag storage

system to 3.4 million African households – a total of 47.6 million people. The program goal is to

see 50% of all farm-level cowpea in West Africa stored utilizing non-chemical hermetic storage

technologies by the end of the 5-year project. Conservative estimates prescribe the savings of this

technology to yield $255 million dollars annually if utilized by 50% of the population in Africa.

Direct benefits will include avoiding loss of cowpeas by the weevil as well as an option for on-

site storage of cowpeas until market price is deemed attractive. Insecticide use on stored cowpeas

should be reduced as well. Additional results could include a new entrepreneurial opportunity in

the area of bag manufacturing and distribution, higher incomes for African families, as well as

increased levels of safe, nutritious food on the African family table.

Trade in cowpea is severely hampered by storage insects, especially the cowpea weevil

(Murdock et al., 1997), which attacks the grains after it has been threshed. Unprotected cowpea

can be destroyed by the cowpea weevil after only two or three months. Farmers use a variety of

traditional storage methods, but recent research estimate a 25% total loss in storage throughout

West Africa. Storage insecticides can be used to control cowpea weevils, but farmers that lack

resources often do not have access to these insecticides and when they do, they may misuse

them, resulting in health and environmental problems.

Beginning in 1987, the United States Agency for International Development (USAID)-funded

Bean/Cowpea Collaborative Research Program (CRSP) developed a portfolio of non-chemical

methods for cowpea storage. Carried out by Larry Murdock and his team of Purdue University

researchers and extension specialists, along with their partners, this program resulted in the

improvement of multiple storage methods: DRUM STORAGE, ASH STORAGE, SOLAR

DESINFESTATIONS and TRIPLE BAGGING.

Research by Moussa (2006) revealed that many farmers were not using the improved storage

technologies because the information did not reach to them and/or the appropriate storage

materials were not available. This demonstrates the importance of implementing an explicit

extension/outreach program in order to experience the full impact of the improved technology.

INTRODUCTION

PROBLEM STATEMENT

IMPROVED COWPEA STORAGE METHODS PURDUE COWPEA STORAGE

CURRENT PROGRAM

CONCLUSIONS

SELECTED BIBLIOGRAPHY

¹Professor, Department of Agricultural Economics, Purdue University

²Entomologis,t Department of Entomology, Purdue University

³Ph.D. Research Assistant, Department of Agricultural Economics, Purdue University4International 4-H Coordinator, International Programs in Agriculture, Purdue University5International Extension Program Coordinator , International Programs in Agriculture, Purdue University6Professor and Associate Dean, International Programs in Agriculture, Purdue University

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Present Value Benefits for Improved

Cowpea Storage Methods

Ash Method Double-TripleBag Metal Drum