Diversity, Population Dynamics, and Damage Intensity of Insect Pests Associated with Oil Palm (Elaeis guineensis Jacq.) in Southwestern Côte d’Ivoire Industrial Plantations

Understanding the composition and dynamics of insect pest communities is crucial for developing effective and sustainable management strategies in oil palm (Elaeis guineensis Jacq.) production systems. This study provides an updated inventory and ecological analysis of insect pests associated with industrial oil palm plantations in southwestern Côte d’Ivoire. The objective was to characterize pest diversity, abundance, and damage intensity across plantations of different phenological stages. Sampling was conducted during the late rainy to early dry season (March to July 2024) across three strata: Young Non-Productive Crops (YNPC), Young Productive Crops (YPC), and Mature Crops (MC). A total of 30,380, 717, and 882 palms were respectively examined in these strata. Insects were collected from a single frond per tree and identified using both morphological keys and image-recognition tools, with confirmation at the Entomology and Agricultural Zoology Laboratory of INP-HB (Yamoussoukro). Ecological indices, including species richness (S), Shannon diversity (H′), evenness (E), and similarity (Jaccard and Sørensen), were calculated to compare community structures. Ten pest species belonging to nine families and three orders (Coleoptera, Lepidoptera, and Orthoptera) were recorded. Species composition varied markedly with plantation age. Oryctes monoceros dominated in YNPC (Ar = 100%), Zonocerus variegatus in YPC (Ar = 72.14%), and Coelaenomenodera lameensis in MC (Ar = 91.70%). Species richness and diversity increased with age (S = 1 to 8; H′ = 0 to 0.72), whereas evenness remained low (E ≤ 0.24), indicating strong dominance by a few species. Similarity indices revealed complete faunal turnover between young and mature strata, confirming a clear ecological succession. Multivariate analyses revealed near-complete faunal turnover between strata (ANOSIM R = 1.0, p = 0.001), with hierarchical clustering perfectly grouping plots according to plantation age. Damage intensity followed the same trend: minimal in YNPC (mainly due to O. monoceros), moderate in YPC, and severe in MC, where C. lameensis caused up to 78.68% moderate and 2.49% severe damage. These results demonstrate that pest pressure and community complexity increase with the maturity of oil palm. Effective pest management, therefore, requires a phenology-based integrated approach, combining preventive measures in young plantations with regular entomological monitoring and biological or selective chemical control in mature ones. Continuous surveillance and the conservation of natural enemies are crucial for enhancing the ecological resilience and sustainability of Ivorian oil palm agroecosystems.