Entomofaunal diversity in cowpea [Vigna unguiculata (L.) Walp.] cultivation systems within the cotton-growing zone of central Benin

Cowpea productivity in Benin remains low, largely due to multiple constraints-chief among them, insect infestations. Despite this, few studies have comprehensively examined the insect fauna associated with cowpea, limiting the development of targeted and effective management strategies. This study addresses the gap by investigating the entomofaunal diversity within cowpea cropping systems in the Central Benin cotton zone. Field sampling was conducted during the rainy season, from July to October 2024, across three distinct sites. The methodology included direct observations, insect collection from plants, and the use of buried traps. A total of 79 insect species, spanning 73 genera and 37 families across seven orders, were identified. The most represented were Hemiptera (34%), Coleoptera (25%), Lepidoptera (16%), Diptera (10%), Thysanoptera (6%), Orthoptera (5%), and Hymenoptera (3%). Biodiversity indices-Shannon (2.78 – 2.81), Equitability (0.67 – 0.80), and Simpson (0.91) — indicate a high level of species diversity, with a slight dominance of individuals from a few key families. These included Chrysomelidae, Crambidae, Aphididae, Coreidae, Cicadellidae, Agromyzidae, and Thripidae. Analysis of functional groups across cowpea phenological stages revealed a marked predominance of pest species over beneficial insects throughout the crop cycle. These findings highlighted the rich insect biodiversity within cowpea ecosystems in central Benin, while also underscoring a functional imbalance driven by pest dominance. The results advocate for integrated management strategies that prioritize the conservation of beneficial insects and the continuous monitoring of pest populations to enhance cowpea productivity.