Smallholders' acceptance of innovations depends largely on the approach used to take their needs and constraints into account. The adoption of integrated pest management (IPM) strategies by smallholders can lead to a reduction in pesticide use in cotton, as soon as the recommended cropping practices are adapted to local conditions and associated with a threshold-based use of chemicals. To achieve this goal, farmers need to be trained on the biological basis of IPM. To ensure effective and rational implementation of IPM by farmers, it is essential to overcome constraints associated with pest scouting, identifying and preserving beneficial insects, and gaining access to the right inputs on time. In the current African context, where the extension system is sometimes in very poor shape, participatory methods fostered by the 'farmer field school' concept could enable farmers to implement an integrated approach to pest management, while keeping researchers informed about farmers' needs and constraints. Our paper is an attempt to use such a participatory method as a tool to explore farmers' needs and constraints when smallholders are asked to adopt an integrated approach to cotton pest management.

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Pyrethroid resistance in Helicoverpa armigera (Hübner) field populations was investigated in Benin over several years by using third- and fourth-instar larval topicalbioassays. H. armigera was resistant to pyrethroids tested as cypermethrin, deltamethrin, bifenthrin, and fenvalerate. Pretreatment with piperonyl butoxide significantly decreased the LD50 value of cypermethrin and deltamethrin, and the resistance suppression by this synergist effect was observed. No significant decrease in the LD50 value was obtained when S,S,S-tributyl phosphoro-trithioate was applied before deltamethrin. In the field, cypermethrin's LD50 value varied, and the highest LD50 values were observed during the rainy season, the cotton, Gossypium hirsutum L., crop period, when pyrethroids are extensively used. In the dry season when there was no cotton cultivation, the lowest LD50 values were obtained. However, reversion was never total in the field; resistance did not revert to the level we observed in the susceptible strain. In the laboratory, when field populations were reared in insecticide-free conditions, resistance decreased and total reversion was observed. Results are discussed with regard to insecticide resistance fitness cost and resistance management strategies.

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