Natural Infestation of Coelaenomenodera lameensis (Coleoptera: Chrysomelidae-Hispinae) by Entomopathogenic Fungi in Oil Palm Groves in the Southern Part of Côte d’Ivoire

Abstract

In Côte d'Ivoire, oil palms generate approximately 3.15% of GDP. They provide a livelihood for more than 2 000.000 people, generating 200.000 regular jobs. Despite its importance, oil palms are exposed to numerous pests, the most significant of which is the leaf miner Coelaenomenodera lameensis (Coleoptera, Chrysomelidae: Hispinae). The fight against this pest is mainly based on the use of chemical insecticides. In the current context of sustainable agriculture and environmental preservation, biological control is a less dangerous and more environmentally friendly alternative. The overall objective of this study is to inventory the entomopathogenic fungi responsible for the death of C. lameensis under natural conditions on oil palm tree. The study was conducted in oil palm production areas in the southern part of Côte d'Ivoire, in village and industrial plantations. The diagnosis, based on the assessment of C. lameensis larval and adult indexes and the counting of dead individuals on leaflets, revealed a very high adult index at CNRA-Divo with 62.59 ± 8.41 adults per palm and, to a lesser extent, at Palmafrique-Anguédédou (4.54 ± 1.86 adults per palm) and Palmci-Boubo (Divo) in industrial plantations (4.99 ± 0.67 adults per palm). However, larval indexes remained low overall. In village plantations, the level of larval infestation was generally low, but the highest was 3.63 ± 1.34 larvae per palm at Palmci-Boubo (Divo). The rate of fungal infestation of the pest was higher in Palmafrique-Anguédédou (60.99 ± 5.79%) in village plantations, while in industrial plantations it was observed at CNRA-Dabou with 26.92 ± 12.48% of C. lameensis adults parasitized. Five entomopathogenic fungi were isolated from dead C. lameensis adults with fungal mycelium on their bodies. These include Aspergillus niger, Aspergillus sp., Cordiceps sp., Isaria sp., Metarhizium sp., and Penicillium sp. For better use of these fungi against this pest, it seems wise to conduct pathogenicity tests to confirm their actual responsibility for the death of the pest in plantations and use as potential microbial agents.