Reducing postharvest losses of bean seeds during storage by using essential oil from Mondia whitei (Hook. f.)

During storage, Acanthoscelides obtectus causes deterioration of bean seeds and offers favorable conditions for fungi development. To prevent losses, the application of chemical pesticides is the most effective method, but it can cause both health and environmental problems. Therefore, researchers have developed Plant-based products that could serve as potential alternatives. This study assessed the efficiency of essential oil from Mondia whitei roots (MWEO) in the preservation of bean seeds. This oil was extracted from the roots by hydro-distillation with a yield of 1.5%. Gas Chromatography-Flame Ionization Detector (GC-FID) and Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed that MWEO was rich in 2-hydroxy-4-methoxy-benzaldehyde accounting for 81%. The activity of this oil as an insecticide was evaluated both through contact and fumigation toxicity tests. Furthermore, the impact of the tested oil on germination of bean seeds and the inhibition of F1 progeny production of insects were investigated. MWEO exhibited excellent toxicity against adult A. obtectus with Lethal Dose 50 (LD 50 ) of 0.15 µl/cm 3 and 0.80 µl/g by fumigation and contact bioassay respectively. Compared to the control, MWEO significantly reduced F1 adult emergence and grain weight loss. However, it shows adverse effects on germination capability of seeds 3 months after treatment. The antifungal activity was assessed on some fungi strains previously isolated on bean seeds. Amongst the fungi tested, Aspergillus niger was the most susceptible with Minimum Inhibitory Concentration of 0.06 mg/ml. Our findings suggest that MWEO has a promising antifungal and insecticidal activities, and can therefore be used as a natural alternative and/or complementary to chemical pesticides.