Diversity and Abundance of Pest Insects Associated with <i>Vigna unguiculata</i> (L.) Walp., 1843 (Fabales: Fabaceae) in Bockle and Dang Localities (North-Cameroon)

Abstract

Cowpea plants are damaged by insects in North-Cameroon. During ecological survey (2021 and 2022) in 44 plots of 4x3.5 m each, insects were captured on stems, leaves, flowers and pods, stored in vials containing 70° alcohol, identified in laboratory and the community structure was characterized. We captured 26,015 adults belonging to six orders, 13 families, 19 genera and 19 species. Coleoptera, Hemiptera and Hymenoptera were species-rich orders [five species each (26.3%)]. Hemiptera was mostly abundant (40.0%) followed by Coleoptera (27.6%), Hymenoptera (21.9%), Lepidoptera (0.9%). Heteroptera and Orthoptera were least abundant (0.8% respectively). We recorded five (26.3%) useful species [the West African predator species <i>Cheilomenes sulphurea</i> (Coleoptera: Coccinellidae), and four (21.1%) afrotropical Apidae species [<i>Apis mellifera adamsonni</i>, <i>Amegilla calens</i>, <i>Amegilla</i> sp. and <i>Xylocopa olivacea</i>]], seven (36.8%) phytophagous species [the indomalayan native <i>Aulacophora indica</i> (Coleoptera: Chrysomelidae), Nearctic native <i>Danaus plexippus</i> (Lepidoptera: Nymphalidae), Palaearctic native <i>Dolerus</i> sp. (Hymenoptera: Tenthredinidae), afrotropical native <i>Hypolimnas misippus</i> (Lepidoptera: Nymphalidae), afrotropical native <i>Monolepta marginella</i> (Coleoptera: Chrysomelidae), Palaearctic native <i>Phyllotreta cruciferae</i> (Coleoptera: Chrysomelidae) and the Eurasian native <i>Tettigonia viridissima</i> (Orthoptera: Tettigoniidae)]. We recorded seven (36.8%) sap-feeding species [the afrotropical native <i>Anoplocnemis curvipes</i> (Hemiptera: Coreidae), cosmopolitan Palaearctic native <i>Aphis crassivora</i> (Hemiptera: Aphididae), old world native <i>Bothrogonia</i> sp. (Hemiptera: Cicadellidae), subtropical native <i>Dysdercus cingulata</i> (Hemiptera: Pyrrhocoridae), western Palaearctic native <i>Lagria hirta</i> (Coleoptera: Tenebrionidae), North American native <i>Poecilocapsus</i> sp. (Hemiptera: Miridae) and the Palaearctic native <i>Riptortus dentipes</i> (Heteroptera: Alydidae)]. Giving up eight (42.1%) native species, 11 (57.9%) non-native species and 14 (73.7%) pest species [three natives species (15.8%) and 11 non-natives species (57.9%)]. The abundant species were <i>M. marginella</i> (39.9%), <i>Poecilocapsus</i> sp. (14.4%), Au. indica (11.4%), <i>Ph. cruciferae</i> (10.4%), <i>C. sulphurea</i> (4.6%), <i>H. misippus</i> (3.7%), L. hirta (3.4%), <i>Ah. crassivora</i> (2.4%) while 11 species (57.9%) were rare (<2.2% each). Insects associated with cowpea consisted mostly of non-native species and the situation calls for more research on the bio-ecology of recorded pests. Cowpea plants’ insect assemblage mostly presented in Bockle and Dang, a fairly significant regeneration force (Zipf and Zipf-Mandelbrot functioning models) and all conditions combine to soar. Due to the numerical and behavioural dominance of non-native insects, a significant number of resources are potentially exploitable. In due course, once the invaders would monopolize available resources and saturate the localities, they would not allow native species the niche opportunities to re-establish themselves. The consequences of loosing native species, which may well interact with the endemic flora and fauna, will be of extreme concern.