Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/1/2002
Publication Date: 5/1/2002
Citation: MEIKLE, W.G., MARKHAM, R., NANSEN, C., HOLST, N., DEGBEY, P., AZOMA, K., KORIE, S. PEST MANAGEMENT IN TRADITIONAL MAIZE STORES IN WEST AFRICA: A FARMER'S PERSPECTIVE. JOURNAL OF ECONOMIC ENTOMOLOGY. 2002. Interpretive Summary: 1. Problem: Prostephanus truncatus, a beetle, is an important introduced pest of stored maize and cassava in Africa. This paper attempted to determine a) whether the beetle is still a pest and whether the natural enemy introduced against the pest worked well; b) whether prophylactically treating the grain stores, where farmers intend to keep grain for up to 9 months to a year, with pesticide was a good idea to protect stores from that beetle and/ or to save money by protecting the store from other pests; and c) whether a rapid scouting program developed in other papers could have been useful. 2. Approach: 2 experimental grain stores were set up in each of 13 sites located in 3 regions of Benin, West Africa. One store at each site was treated with pesticide and the other was not. All 26 grain stores were sampled once per month, as well as farmer grain stores in 11 of the sites. All pests were counted, damage and loss was recorded, and market prices for maize were obtained. 3. Results: The beetle was found in over half the grain stores, even though the natural enemy was well established, so the beetle is still a problem even though the natural enemy is there. Prophylactic treatment of stores with pesticide did not protect them fully against attack by the beetle, and kept other pests down for up to 5 months but no longer. Pesticide did pay for itself in the first 5 months, but later in the season maize prices went up and people accepted more damage in market maize, so pesticide treatment became less valuable. The scouting program would have been useful, and could have been used even in stores that were treated to help manage them.
Technical Abstract: Farmers in Benin have few resources to invest in protection of stored maize, and prophylactic pesticide application is often recommended by extension and development agencies. Neither the efficacy nor profitability of such an application in traditional maize stores has been addressed quantitatively. In this study, existing management options for stored maize in southern Benin were evaluated with respect to their effects on grain injury and on densities of Prostephanus truncatus (Horn) and Sitophilus zeamais Motschulsky. P. truncatus infested 54% of the experimental stores in the study, even though Teretrius nigrescens, a natural enemy introduced against P. truncatus, was well established in the region. S. zeamais was the most common pest, found in 85% of the experimental stores. Prophylactic pesticide application was found profitable in the first five mo, where profitable was defined as a greater value of a prophylactically-treated store than an untreated store, after taking into account market price, pesticide costs, percentage grain damage and weight loss. After six mo, however, treated stores were not significantly different in terms of either percentage damage or profit from untreated stores. A rapid scouting plan intended to provide farmers with a means for identifying stores at greatest risk of severe P. truncatus infestation was field validated. Given that in practice unsafe pesticide use is prevalent, research and extension services should clearly state the limitations to prophylactic treatment and increase the effort to educate farmers on appropriate pesticide use, store monitoring and marketing.