Insect repellent and insecticidal potential of two Eucalyptus species essential oils from subtropical desert climate

In the present study, in order to search greener solution for food insects, the insecticidal and insect repellent potentials of e. oils of E. camaldulensis and E. citriodora leaves (different concentrations) have been evaluated against two stored food insects, i.e., rice weevil (Sitophilus oryzae) and red flour beetle (Tribolium castaneum). Insecticidal activity of these e. oils against Sitophilus oryzae (rice weevil) showed 76.67% mortality for E. citriodora and 40% for E. camaldulensis e. oil (100 mu L/mL in each case), after 96 contact hours. For Tribolium castaneum (red flour beetle), 66.67% mortality rate of E. camaldulensis e. oil was achieved by100 mu L/mL essential oil after 96 contact hours while 76.67% for E. citriodora e. oil at same concentration. The % repellent activity of both e. oils showed that it decreased with exposure time but increased with concentrations of essential oil. Hence the repellent activity of 100 mu L/mL concentration of E. camaldulensis e. oil against Sitophilus oryzae (rice weevil) was 90% after 24 h which decreased up to 76.67% after 96 h of exposure time. In case of E. citriodora e. oil, % repellency against same insect was found to be 73.33% for 100 mu L/mL concentration which decreased up to 56.67% after same time interval. In case of Tribolium castaneum (red flour beetle), the repellent activity of 100 mu L/mL E. camaldulensis e. oil was 86.67% after 24 h and decreased to 73.33% after 96 h' exposure. The 100 mu L/mL E. citriodora e. oil was having repellent activity 76.67% after 24 h which decreased to 60% after 96 h. Differences in insecticidal and insect repellent activities of two essential oils were found to be associated with major chemical components as indicated by GC-MS analysis. This study suggests that combination of these two e. oils can be very effective to repel as well as kill the food born insects. Also, these e. oils can be proved excellent green alternative of environmental damaging synthetic pesticides.