Low fruit set rates in oil palm plantations may be related to inadequate entomophilous pollination. The objective of this study was to follow the variations of fruit set and to determine its relationships with the entomofauna visiting inflorescences at La Mé, Grand-Béréby and Iboké in Côte d’Ivoire. Densities of the insects were followed out on male and female inflorescences during 12 months. The fruit set rate was also monitored over the same period on young bunches. The results showed that pollination is provided by Elaeidobius kamerunicus, Elaeidobius plagiatus, Elaeidobius singularis, Elaeidobius subvittatus, Microporum congolense, Microporum dispar and Atheta burgeoni. At La Mé, the fruit set rate was negatively correlated with the damage of Prosœustus spp (r = -0.43, p = 0.01) and positively with the abundance of E. kamerunicus and E. plagiatus on female flowers (respectively: r = 0.60, p = 0.002 and r = 0.47, p = 0.020). At Grand-Béréby, it is negatively correlated with the damage of Prosœustus spp (r = -0.42, p = 0.01). At Iboké, positive correlations were observed with the density of E. subvittatus (r = 0.40, p ˂ 0.001), M. congolense (r = 0.41, p = 0.046), M. dispar (r = 0.57, p = 0.004) and A. burgeoni (r = 0.65, p ˂ 0.001). This study highlighted the necessity to manage the populations of pollinators and the inflorescences pest insects to improve the production of oil palm in Côte d'Ivoire.

Prosoestus sculptilis and Prosoestus minor (Coleoptera, Curculionidae) are female inflorescences of the oil palm pest. These insects can cause a considerable decrease (about 40%) of the setting rate. The currently proposed control method is the chemical control with the use of thiocyclam-hydrogen-oxalate, derived from the Nereistoxin. For sustainable agriculture, it is appropriate to use an integrated pest management system, including biological control. The purpose of this work is to contribute to the biological control of Prosoestus spp. by the use of Metarhizium anisopliae, entomopathogenic fungus, to improve fruit set rate of oil palm. A screening of five (05) isolates of the fungus was performed by passive and active suspensions inoculation of spores in increasing concentrations. Coded isolates CNRA-BME2 and CNRA-BME5 were most virulent for these insects with mortality rates of approximately 80% during the passive inoculation on fungic cultures. The concentration c = 10 9 spores/mL was optimal during active inoculation. Metarhizium anisopliae is therefore a potential biological control agent against Prosoestus.