Seed Yield Improvement in Vigna unguiculata (L.) (Fabaceae): Efficiency of Pollinators and Impact of Aqueous Leaf Extract of Three Plant Species in North Cameroon

Abstract

Aims: Because of the problems in agroecosystems following the anarchic use of synthetic insecticides, studies propose an alternative, the use of botanical biopesticides against pests.
 Study Design: The present study was conducted to evaluate (1) the potential of leaf extract of Calotropis procera (Gentianales: Apocynaceae), Eucalyptus camaldulensis (Myrtales: Myrtaceae) and Tithonia diversifolia (Asterales: Asteraceae) against insects and (2) impact of Apis mellifera (Hymenoptera: Apidae) on Vigna unguiculata (Fabales: Fabaceae) seed yield in North Cameroon.
 Place and Duration of Study: A field study was set up in 2021 in North Cameroon, during the rainy season. Fourthy four plots of 4x3.5 m each were distributed according to a randomized complete block design model comprising four untreated, four treated using parastar (40EC 535/10/IN, 20 g/l imidaclopride and 20 g/l lamda-cyhalothrine), and 36 plots treated using 10%, 20% and 30% aqueous leaf extracts separately sprayed against Aphis craccivora (Hemiptera: Aphididae).
 Methodology: Four groups of flowers were randomly selected: (1) free, (2) protected from insects, (3) free exclusively to Ap. mellifera and (4) protected against insects.
 Results: A total of 10,984 captured flower insects belonged to three orders (Hemiptera, Hymenoptera and Lepidoptera), three families (Aphididae, Apidae and Nymphalidae) and seven species [one (14.3%) sap-sucking Aphis craccivora (Hemiptera: Aphididae), four (57.1%) pollinators Hymenoptera Apidae [Amegilla calens, Amegilla sp., Apis mellifera and Xylocopa olivacea] and two (28.6%) Lepidoptera Nymphalidae [Danaus plexippus and Hypolimnas misippus]. A total of 7,425 insects associated with V. unguiculara corresponded to four orders [Hemiptera (56.7%), Coleoptera (41.5%), Heteroptera and Orthoptera with 0.9% respectively], nine families [Aphididae (45.3%), Chrysomelidae (38.7%), Pyrrhocoridae (4.8%), Coreidae (3.8%), Cicadellidae (2.8%), Coccinellidae (1.9%), Alydidae, Tenebrionidae and Tettigoniidae with 0.9% respectively], 11 genera and 11 species.
 Conclusion: Apis mellifera was the major pollinator and Aphis crassivora the major pest. The seed yield was improved by 30% extract of plants without impact on pollinators.