Insecticidal Effects of Aqueous Extracts of Carica papaya, Tithonia diversifolia and Strychnos spinosa Leaves on the Population Density of Aphis gossypii and the Foraging Activity of Apis mellifera on Bell Pepper in Ngaoundéré, Cameroon

Abstract

Aims: This study was conducted to evaluate the insecticidal effects of aqueous extracts from Carica papaya, Tithonia diversifolia, and Strychnos spinosa leaves on Aphis gossypii population density and Apis mellifera foraging activity in an experimental field of Capsicum annuum. Study Design: The trials were arranged in a completely randomized block with nine treatments, repeated four times. These included three insecticide treatments, a negative and a positive control to evaluate the population density of A. gossypii, and four treatments to study the activity of honey bees. Place and Duration of Study: The study was carried out in Ngaoundéré (Adamawa, Cameroon) from August to December 2020 and from March to July 2021. Methodology: Bell pepper plants were sprayed from the bud stage until fruit ripening at 14-day intervals. The population density of A. gossypii was recorded, and the foraging activity of A. mellifera was monitored. Results: All bio-insecticide treatments significantly reduced the population density of A. gossypii. The highest density was observed during the rainy season (9.27 ± 1.44) compared to the dry season (5.37 ± 1.35). Among the four insect pollinators recorded on C. annuum flowers, A. mellifera ranked first, accounting for 95.45% and 63.39% of visits in the rainy and dry seasons, respectively. The bees exclusively collected nectar from C. annuum flowers. Foraging activity occurred between 7 a.m. and 1 p.m., with peaks between 10 a.m. and 11 a.m. for all treatments except S. spinosa, which peaked between 8 a.m. and 9 a.m. during the rainy season. In the dry season, a single peak of activity was observed between 10 a.m. and 11 a.m. for all treatments. The abundance of A. mellifera per 1,000 flowers and the mean duration of visits were higher in the C. papaya and T. diversifolia treatments during both seasons. Conclusion: Apis mellifera was the most dominant pollinator, while Aphis gossypii was the major pest. To protect bell peppers from insect pests while preserving pollinators, especially A. mellifera, botanical insecticides should be considered as an alternative to synthetic insecticides.