Evaluation of Six Plant Essential Oils against Three Stored Product Insects and Their Effects on the Haemogram under Laboratory Conditions

Abstract

The effect of six plant essential oils against three stored grain insects, Sitophilus oryzae, Rhizopertha dominica and Tribolium castaneum were studied under laboratory conditions. The tested oils are namely, fennel oil (Foeniculum vulgare), caraway oil (Carum carvi), cinnamon oil (Cinnamomum verum), citronella oil (Cymbopogon winterianus), nutmeg oil (Myristica fragrans) and black cumin oil (Nigella sativa). The result showed that increasing of the oil concentration and exposure times significantly increased the mortality percentage. Generally, the toxicity of essential oils at all tested concentrations increased with the increasing of exposure time. So, the results indicated that toxicity of all tested essential oil against the three stored grain insects at the high concentration was recorded high mortality faster than low concentration. The tested essential oils significantly decreased the different haemocyte counts in tested insects, cinnamon oil markedly increased the haemocyte surface areas in the tested insects especially the surface area of oenocytoides in T. castaneum. The recorded results indicate that the essential oils of fennel, caraway, cinnamon and citronella could be applicable to the management of S. oryzae, R. dominica and T. castaneum adults.