Insecticidal and Repellent Actions of Methanolic Extracts from Five Medicinal Plants against the Saw-Toothed Grain Beetle Oryzaephilus surinamensis (Linn.) (Coleoptera: Silvanidae)

Abstract

The insecticidal and repellent activities of methanolic extracts of Ruta chalepensis L. (Rutaceae: Sapindales), Rhazya stricta Decne (Apocynaceae: Gentianales), Heliotropium bacciferum Forssk (Boraginales: Boraginaceae), Salvadora persica L. (Salvadoraceae: Brassicales), and Moringa oleifera L. (Moringaceae: Brassicales) were investigated against the saw-toothed grain beetle Oryzaephilus surinamensis L. (Coleoptera: Silvanidae). Results demonstrated that all these plant extracts had variable toxicity against the beetle. The effectiveness of the tested plant extracts was shown by increasing the used concentrations. The methanolic extract from R. stricta performed the best and was able to cause 93.3% and 89.2% mortality for the adult and larval stage of O. surinamensis, respectively, at 500 ppm after six days of plant extract treatment. The tested extract of S. persica at 500 ppm caused 80.8% and 82.5% mortality on larvae and adults of O. surinamensis after six-day of treatment. On the other hand, repellent effects of extracts of R. stricta, S. persica, and R. chalepensis at 500 ppm were recorded, with higher values of 91.7%, 83.3%, and 78%, respectively, against the adults of O. surinamensis, which were under 500 ppm. These extracts especially from R. stricta, S. spinosa, and R. chalepensis could be useful to prevent damages and store grain production losses for O. surinamensis.