Diversity and Abundance of Pest Insects Associated with Solanum aethiopicum Linnaeus, 1756 (Solanaceae) in Balessing (West-Cameroon)

Despite chemical treatments, all development stages of Solanum aethiopicum Linnaeus, 1756 plants are damaged in the field by insects in Balessing locality (West-Cameroon). During ecological surveys conducted from July to October 2020 in 11 plots presenting four development stages: seedlings (St1), fruit setting plants (St2), flowering phase plants (St3), and fruiting phase plants (St4). Insects active on stems, leaves, flowers and fruits, were captured, identified and the community structure was characterized. Abundance of each species and the part of the plant attacked were noted. Specimens were stored in vials containing 70° alcohol while immature insects were reared in the laboratory till the adult emergence. A total of 155 specimens collected in the field belonged to four orders, 13 families and 22 species. Lepidoptera and Hemiptera were most abundant (38.7% and 34.8% of the total collection respectively). Coleoptera and Orthoptera were least abundant (14.2% and 12.3% respectively). In the laboratory rearing, two Lepidoptera emerged from reared caterpillars: the Crambidae (Leucinodes orbonalis Guenee, 1854) and the Noctuidae [Helicoverpa armigera (Hubner, 1808)]. This gives a total of four orders, 14 families, 22 genera and 23 species associated with eggplant plants. In the field, plants were damaged by three borer species (13.0%) [Phrissotrichum grenieri (Desbrochers, 1875) (Coleoptera, Brentidae), Le. orbonalis (Lepidoptera, Crambidae) and H. armigera (Lepidoptera, Noctuidae)], by five phytophagous pest species (21.7%) [Lagria villosa (Fabricius, 1781) (Coleoptera, Tenebrionidae), Leptoglossus occidentalis Heidemann, 1910 (Hemiptera, Coreidae), Manduca sexta Linnaeus, 1763 (Lepidoptera, Sphingidae), Sphaerocoris annulus (Fabricius, 1775) (Hemiptera, Scutelleridae) and Taphronota ferruginea (Fabricius, 1781) (Orthoptera, Pyrgomorphidae)], three sap-feeding species (13.0%) [Dysdercus volkeri (Schmidt, 1932) (Hemiptera, Pyrrhocoridae), Edessa rufomarginata (De Geer, 1773) (Hemiptera, Pentatomidae) and Gonocerus acuteangularis (Goeze, 1778) (Hemiptera, Coreidae)] and 12 species of unknown pest-status. We recorded 11 pest species (47.8% of the total species richness) [six (26.1%) non-native and five (21.7%) native species]. Coleoptera presented a high number of species (34.8%) followed by Hemiptera (30.4%), Orthoptera (21.7%) and Lepidoptera (13.0%). Lepidoptera Crambidae (38.1%) was the most represented, followed by Hemiptera Pentatomidae (14.1%), Orthoptera Acrididae (10.2%), Hemiptera Coreidae and Hemiptera Pyrrhocoridae (7.7% respectively), Hemiptera Scutelleridae (5.2%), Coleoptera Tenebrionidae (5.1%), Coleoptera Chrysomelidae (4.5%), Orthoptera Pyrgomorphidae (3.9%) and Coleoptera Brentidae (1.3%). Three families (Carabidae, Sphingidae and Scarabeidae) were rare (<1% of the total collection). Chemicals were not efficient in Balessing, since entomofauna associated with eggplant plants remained diverse and consisted mostly of alien species. The situation calls for more research on the bio-ecology of the recorded pests with further goal of developing sustainable management strategies to reduce yield losses.