Bioinsecticidal potential of rose essential oil against the cowpea beetle, Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae)

Abstract

Callosobruchus maculatus (Fabricius), also known as the cowpea beetle or pulse beetle, is the most important pest of stored cowpea. The beetle causes both qualitative and quantitative losses in the grains, all of which result in low crop yields. The objective of this work was to investigate the insecticidal effect of rose essential oil (REO) on adult Callosobruchus maculatus in terms of mortality and oviposition. In addition, the viable mesophilic aerobic bacteria of C. maculatus were evaluated, and surface molecular electrostatic potential (MEP) maps were examined to determine the interaction domains of the bioactive components of REO. The interaction mechanism between the AChE enzyme (PDB ID: 6XXY, 4EY6, 4EY7 and 6O4W) and the REO components was investigated using the molecular docking method. The highest mortality of 92.40 ± 0.03% was obtained at 16 μL within 72 h of exposure. Higher concentrations of the essential oil decreased the laying performance of C. maculatus. A significant decrease of 91.33% in the number of eggs laid was observed. Gas chromatography–mass spectrometry (GC/MS) results showed that the major constituents of Rosa damascena Miller essential oil (REO) were citronellol (46.15%), geraniol (16.19%), nonadecane (8.80%) and nerol (7.43%). Treatments of 4, 8, 12 and 16 μL of REO significantly reduced the viable mesophilic aerobic bacteria of C. maculatus samples compared with the control. It was found that the most effective binding was between the REO components and the 4EY7 protein, with binding energies ranging from −6.9 to −8.9 kcal/mol. Although the major component of REO was citronellol (46.15%), the best interaction was observed with farnesol isomer B (0.80%). Overall, these results suggest that REO has the potential to control C. maculatus as an environmentally friendly alternative to synthetic pesticides.