In the present study, the synergistic effects of Beauveria bassiana (Bals.-Criv. Vuill.) (isolate Bb11) and Bacillus thuringiensis var. kurstaki (Berliner) with neem oil were evaluated in three agroecological zones in Bénin. Four bioinsecticide treatments (neem oil, neem oil and B. bassiana used separately for different target pests, neem oil mixed with B. bassiana and neem oil mixed with B. thuringiensis) were compared with a calendar-based treatment using synthetic insecticides and a control without insecticides. The bioinsecticide treatments were less effective than the calendar-based treatment at controlling cotton pests. There was no difference in yields and the number of damaged bolls in plots under treatments with the four bioinsecticide formulations, suggesting an absence of synergy between neem oil and B. bassiana and neem oil and B. thuringiensis. The numbers of natural enemies in all the bioinsecticide treatment plots and the control plots were similar and higher than those in the calendar-based treatment plots. The highest yield and profitability were obtained with the calendar-based treatment. Screening the compatibility of plant-based products and biopesticides through bioassays is essential for a successful application of their combinations in any integrated pest management strategy.

The bioefficacy of various plant extracts, namely Azadirachta indica A. Juss, Khaya senegalensis Desrousseaux (A. Jussieu) and Hyptis suavuolens (L.) Poit, either alone or in combination with half the recommended dose of synthetic pesticides, was studied with farmers to find a more sustainable strategy for the management of bollworms in cotton. A number of treatments were farmer innovations. The treatments were compared six times during the season to the application of the fully recommended dose of synthetic pesticides and to a control with no pesticide application. Applications of either the fully recommended dose of the synthetic pesticides or the combinations with a neem seed extract (6 kg/ha) were most effective in reducing bollworm incidence and damage. Both the treatments gave the highest yields of cottonseed, the latter being the most cost-effective. All the pesticides used, except neem alone, had a toxic effect on bollworm predators. This study has increased farmers' confidence in endogenous technology. The researcher's interaction among the local learning group members, who conducted the experiments, facilitated the introduction of a cost-effective alternative to the standard full-dose synthetic pesticide recommendation.