Insecticidal Effect of Thymus citriodorus (Pers.) Schreb (Lamiaceae) Essential Oil on Sitophilus granarius (Linnaeus, 1758) (Coleoptera: Dryophthoridae) and Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae)

Abstract

In the current study, the essential oil of Thymus citriodorus (Pers.) Schreb (Lamiaceae) was evaluated for its ability to control adults of two significant pests of stored products, Sitophilus granarius (Linnaeus, 1758) (Coleoptera: Dryophthoridae) and Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae), under laboratory conditions. Using a microapplicator, test insects were exposed to 0.025, 0.05, 0.1 and 0.15 µl/insect concentrations of plant essential oil in order to assess contact toxicity. At 24, 48, 72, and 96 hours following applications, deaths were noted. The experiment revealed that, depending on the insects and dosages, the essential oil showed varying degrees of contact activity. The essential oil of T. citriodorus generally had low effect on adult T. castaneum, with the greatest effect was 15.32% at 0.15 µl/insect dose after 96 hours. Adults of S. granarius showed greater sensitivity to the essential oil of T. citriodorus. After 48 hours, doses of 0.1 and 0.15 µl/insect concentrations of the essential oil resulted in over 95% of S. granarius adult mortality. The findings of the study indicate that T. citriodorus essential oil has the potential to be used in the control of S. granarius.