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Les investigations ont été faites sur les fleurs de Cajanus cajan en vue d’estimer l’impact de l’activité de Dactylurina staudingeri sur la pollinisation, la production en gousses et en graines à Dang, en 2016 et 2017. Pour chacune de ces années, 540 boutons floraux ont été étiquetés sur 120 plantes réparties en quatre traitements: 120 fleurs laissées en libre pollinisation, 120 fleurs protégées des insectes, 200 fleurs protégées, puis découvertes, visitées exclusivement par D. staudingeri et de nouveau protégées et 100 fleurs protégées, découvertes et à nouveau protégées, sans visite d’insectes ou de tout autre organisme. Le taux de fructification, le nombre moyen de graines par gousse et le pourcentage de graines normales ont été comparés entre ces traitements. Sur 33 espèces d’insectes recensées, D. staudingeri était majoritaire avec 12,19% de 6037 visites. Cette abeille prélevait fortement le nectar et récoltait faiblement le pollen au niveau des fleurs de C. cajan. La vitesse moyenne de butinage était de 7,14 fleurs/min. Via l’efficacité pollinisatrice d’une visite florale, D. staudingeri a augmenté le taux de fructification de 14,71%, le nombre moyen de graines par gousse de 35,29% et le pourcentage de graines normales de 17,31%. La conservation des colonies de D. staudingeri à proximité des exploitations de C. cajan est recommandée pour assurer la hausse des rendements de cette culture et favoriser une bonne pratique de la méliponiculture dans la région.Abstract Investigations were made on the flowers of Cajanus cajan in order to estimate the impact of the activity of Dactylurina staudingeri on pollination and yields at Dang, in 2016 and 2017. For each of these years, 540 flowers buds labeled on 120 plants were divided into four treatments: 120 open-pollinated flowers, 120 bagged flowers, 200 flowers protected, then unbagged, exclusively visited once by D. staudingeri and rebagged, and 100 flowers bagged, unbagged and rebagged without insect or any other organism visit. The fruiting rate, the mean number of seeds per pod and the percentage of normal seeds were compared between these treatments. Among 33 insect species recorded, D. staudingeri was prominent with 12.19% of 6037 visits. This bee harvested intensely nectar and collected slightly pollen from C. cajan flowers. The mean foraging speed was 7.14 flowers/min. Through the pollinating efficiency of a single flower visit, D. staudingeri increased the fruiting rate by 14.71%, the mean number of seeds per pod by 35.29% and the percentage of normal seeds by 17.31%. The conservation of D. staudingeri colonies close to C. cajan farms is recommended to improve yields of the crop and to promote the good meliponiculture in the region.

The study of the variability of the flower visiting entomofauna between Palar and Djarengol-Kodek (Maroua, Cameroon) and the influence of the pollination type were carried out in 2020 for assessing their impact on sesame production. Three treatments of 50 plants each were used according to whether the flowers were open-pollinated (TA) or protected using mosquito net cages (TB) and plastic cages (TC) for analysis. The diversity and composition of the entomofauna were compared between localities from TA as well as the resulting pod and seed yields of the crop. 21 and 12 insect species were found foraging on sesame flowers in Palar and Djarengol-Kodek respectively. Hymenoptera had a high relative abundance ˃ 92% at both sites and played a key role in pollinating the flowers of the host plant species. The diversity index was higher in Palar (H’ = 3.10) than in Djarengol-Kodek (H’ = 2.64). The Jaccard similarity index between both sites was J = 0.43. During their floral activity, these bees promoted autogamy, geitonogamy and xenogamy on S. indicum flowers. The impact of the floral activity of bees on sesame pod and seed yields was in the range of 17.92% - 29.27% and 12.97% - 18.39% in Djarengol-Kodek and Palar respectively with a significant difference between these values (X2 = 156.20; df = 1; P ˂ 0.001 and X2 = 69.74; df = 1; P ˂ 0.001). These differences showed the important role of the variability of the composition and the relative abundance of pollinators on sesame production between sites. Moreover, bee pollination (TA) highly increased anemophily (TB) and cleistogamy (TC) in sesame. Encourage producers to adopt more environmental friendly management methods to help preserve the habitat of sesame pollinator species for better productivity is an important practice.

In the Far-North region of Cameroon, watermelon cultivation still faces several constraints that represent a major threat to fruit production. This requires research for maintaining and improving the crop yields. The present study was aimed at investigating the insect fauna associated with watermelon for its optimal management. Observations allowed the identification of insect-visiting fauna to the crop, to assess the role played by each species on growing watermelon, to evaluate the means of protection used by farmers and to make useful projections towards the biological control of the natural enemies of insect pests. Twenty two insect species visited the vegetative organs of watermelon. Fruit flies were found to be the most common and most damaging group for watermelon production. The larval stage of Syrphidae and adults of Coccinellidae and Formicidae were identified as important biocontrol agents. Watermelon requires effective phytosanitary cover for its optimal production. A non-significant fruit set rate was obtained between experimental treatments (T). The rate of mature fruit was zero in T0 which does not benefit from pollination and health care. Protective means used locally guaranteed the production of mature fruits by 24% in T1 without any sanitary care, 36% in T2 impregnated with neem Azadirachta indica (Meliaceae) leaf’s extract, and 54% in T3 treated with an insecticide named Optimal. Due to the strong involvement of chemicals in the protection of watermelon production at the study site, their use is often a problem for safeguarding the balance of the ecosystem and the health of farmers and consumers. It is therefore essential to promote the use of pollinators and to protect the natural enemies of insect pests to enhance sustainable production of watermelon in Yagoua.