IITA
International Institute of Tropical Agriculture
Projet Lutte Biologique contre les Locustes et les Sauteriaux
BP. 08-0932 Cotonou, Benin
tel. 229 35 05 53/35 01 88 fax 229 35 05 56
IITA-Benin@cgnet.com

By D. Müller¹, C. Gbongboui¹, H. De Groote¹, J. Langewald¹, R. Badou², and Y. Bocco^1
1IITA, Cotonou, ²Service Protection des Végétaux, Porto Novo

Farmers of two villages in Mono province, Benin, in collaboration with researchers of the biological control of locusts and grasshoppers program (LUBILOSA) at IITA, developed a use and marketing strategy for the biopesticide Green Muscle, an oil-based formulation of the entomopathogenic fungus Metarhizium anisopliae var. acridum for the control of Zonocerus variegatus L. Three different doses, two different sprayers and two different periods of control were tested. Farmers preferred the preventive treatment with a medium dose (20 g/ha) by ULV spinning disk sprayer. Half a day of training for a village brigade was found to sufficient to enable them to identify the egg laying areas and to apply the biopesticide. Farmers would prefer the producer to sell the biopesticide on credit, directly to the village association. The village brigade will treat the grasshoppers, and be reimbursed by the concerned farmers.

LUBILOSA Socio-economic Working Paper Series No. 99/2
Paper presented at the regional workshop
"Farmers and scientists in a changing environment: Assessing research in West Africa"
February 22-26, 1999, Cotonou

The variegated grasshopper (Zonocerus variegatus) is the only major grasshopper pest in the humid and subhumid zones of West Africa. It is most active by the end of the second rainy season and all the way through the major dry season. It especially attacks cassava in the major dry season from January to March, when this crop constitues most of the remaining green vegetation. Grasshopper attacks can be very impressive and have generated substantial donor support in the past. However, few studies have treated the economic impact of the variegated grasshopper. Crop losses have been simulated by cutting the leaves or the whole stem during the dry season. While one study found no impact at all (Baumgart 1994), another one (Page et al., 1980) found yield reductions of 36% but only when manual defoliation was carried out at monthly intervals during the dry season from November to March. This study indicates that grasshoppers only reduce cassava yields through damage at the end of the dry season, when natural leaf regeneration starts. No studies of yield loss on other crops are available.

The LUBILOSA program (Lutte Biologique contre les Locustes et Sauteriaux) has developed Green Muscle as a specific biopesticide for the control of locusts and grasshoppers. Green Muscle is an oil-based formulation containing the fungal pathogen Metarhizium anisopliae var. acridum (Prior et al. 1992, Bateman, 1997). After developing the technology, LUBILOSA started a third phase with more emphasis on implementation, incuding socio-economic analysis and farmer participatory research (De Groote, 1997). In 1997, LUBILOSA started a farmer participatory development of a control strategy for the variegated grasshopper, following the 4 standard stages (Werner 1993): exploring the demand, identifying different options, testing different alternatives, and assessing those alternatives.

Preliminary surveys and secondary data led to the hypothesis that demand for grasshopper control in Benin would be highest in the northern part of the Mono province. A survey in the dry season of 1990/1991 showed high variegated grasshopper densities (> 20 grasshoppers/m² ) in most of that area (Paraïso et al. 1992). A survey by the Ecologically Sustainable Cassava Plant Protection (ESCaPP) project in the countries of Nigeria, Benin, Togo and Côte d'Ivoire showed that problems with the variegated grasshopper are most important in the transition zone between rain forest and humid savanna (ESCaPP, unpublished data). For this zone in Benin, North Mono is the only region with substantial cotton production (Colnard 1995). The cotton marketing board has established a credit system to finance inputs, and cotton is the crop with the highest level of insecticide use in Benin. Application of the biopesticide developed by LUBILOSA is similar to that of cotton pesticides, and if it could be purchased through a similar distribution system, demand for the biopesticide can be expected where grasshopper densities are high and where cotton is an import crop. Both of these conditions are met in North Mono. Moreover, this zone falls in IITA's benchmark site for the derived savanna.

This potential demand for a biopesticide against grasshoppers was confirmed during an informal survey in January and February 1997 in 11 villages of North Mono. During group interviews, farmers consistently ranked the grasshoppers among three most important crop pests in their fields. Subsequently, three villages (Hontoui, Eglime and Zouzouvou) were chosen for a farmer participatory development of a grasshopper control strategy. Hontoui was chosen because of highly infested fields, Eglime and Zouzouvou were chosen because the Institut Nationale de Recherche Agronomique du Benin (INRAB) has permanently technicians based here for its research programme "Recherche Développement".

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