Impact of Plant Extracts on the Pollination Activity of <i>Apis mellifera</i> Linnaeus, 1758 (Hymenoptera: Apidae) on Flowers of Cowpea Variety Feekem, in Dang (Adamaoua, Cameroon)

Abstract

Synthetic pesticides present worldwide risks of contamination of humans, livestock and the environment due to the strong persistence and the toxic residues in fruits and vegetables. Natural biopesticides of local plant origin present low persistence and are the best alternative for the control of crop pests. In the Adamaoua region (Northern Cameroon), few studies exist concerning effects of botanical pesticides on the behavior of beneficial insects. Studies aimed to draw up a list of pollinating insects on flowers of <i>Vigna unguiculata </i>(L.) Walp., 1843 (Fabales: Fabaceae), in situations of treatment with botanical pesticides compared to the situation of the use of synthetic insecticide and to determine the effect of the biopesticides on the behavior of the main floricultural insects. Field investigations were carried out during two cowpea cultivation campaigns (June to September 2021 and June to October 2022) in Dang (suburb of Ngaoundere) on the effect of leaves extracts of local plant origin on the foraging behavior of <i>Apis mellifera</i> Linnaeus, 1758 (Hymenoptera: Apidae) and the main sap-sucking insect <i>Aphis craccivora </i>Koch, 1854 (Hemiptera: Aphididae). Forty-four cowpea plots of 4x3.5 m each distributed according to the randomized complete block model (four untreated plots as negative control, four plots treated with the synthetic insecticide Parastar (40EC 535/ 10/IN, 20 g/l of imidacloprid and 20 g/l of lamda-cyhalothrin) as positive control, and 36 experimental plots treated with three concentrations (10%, 20% and 30%) of aqueous leaves extract of <i>Calotropis procera</i> (Gentianales: Apocynaceae), <i>Eucalyptus camaldulensis </i>(Myrtales: Myrtaceae), and <i>Tithonia diversifolia</i> (Asterales: Asteraceae) respectively, made it possible to conduct four treatments: (1) flowers left to freely pollination, (2) flowers protected against pollinators, (3) flowers visited exclusively by <i>Ap. mellifera</i> and (4) flowers protected against insects. Among eight species (four orders, four families and seven genera) recorded on the flowers of <i>V. unguiculata</i>, the domestic bee <i>Ap. mellifera</i> was the most common and collected nectar and pollen. The control plots and those treated with 10% or 20% aqueous leaves extracts allowed the bee to carry out its activity. Plots treated with 30% extract of each plant and those treated with the synthetic insecticide Parastar, drastically altered the rhythm and speed of activity in <i>Ap. mellifera</i> foragers. This behavior became less coordinated and slow on treated plants. It would be wise to use 10% or 20% aqueous extracts as botanical insecticides and an alternative to the synthetic insecticide Parastar.