Biological activity of four plant oils, against the red palm weevil, Rhynchophorus ferrugineus (Oliver), (Coleoptera Curculionidae)

Abstract

In the present study, four botanical oils of Melissa officinalis, Borago officinalis, Laurus nobilis and Carapichea ipecacuanha were tested against newly emerged adult males and females of the red palm weevil, Rhynchophorus ferrugineus (Oliver) for investigating their insecticidal activity, their effects on some bilogical aspects and morphogenetic abnormalities in the all stages.The results revealed that the males of Rhynchophorus ferrugineus were more susceptible to the four botanical oils than the females, followed by the immature larvae. The larvae showed different degrees of susceptibility to the four botanical oils, they showed the highest susceptibility to C. ipecacuanha and the lowest to B. officinalis oil at LC 50 levels. Both adult males and females showed the highest susceptibility to C. ipecacuanha and the lowest to L. nobilis oil at LC 50 levels. Also, the obtained results showed that the four tested oils disrupted some biological aspects of the tested insects. These oils markedly reduced male and female longevity, female fecundity and hatchability of the laid eggs. Morphogenetic abnormalities such as darkness of pupae, incomplete adult eclusion , dwarfism and crumpled wings and legs of adults appeared in the different stages of the insect as a result of treatment with the four tested oils.