Comparing the insecticidal effect of eucalyptus and thyme essential oils on potato aphid (Macrosiphom euphorbiae)

Herbal essential oils are known as suitable alternative for controlling pests due to low toxicity, fast decomposition and environment- friendly. This study aimed to examine the insecticidal effect of two herbal essential oils, i.e. Eucalyptus globulus and Iranian thyme (Zataria multiflora), on potato aphid. In the current study
Herbal essential oils were extracted by distillation with water using a clevenger device. The biometric experiments were performed on adult insects in 6 concentrations of eucalyptus, including 2000, 6000, 10000, 20000, 16000, 20000 ppm and in 6 concentrations of thyme, including 4000, 8000, 10000, 15000, 20000, 24000 ppm. The amount of losses in each experiment was counted during 24 hours after the experiment initiation.
According to the results of the probit data analysis, the values of LC50 and LC90 ​​for eucalyptus essential oil were 4699 and 37106 ppm, respectively, and for thyme essential oil, these values ​​were 11944 and 45620, respectively. In the present research, the highest fatality rates (loss percentage) for eucalyptus essential oil at a concentration of 20000 ppm and for thyme essential oil at a concentration of 24000 ppm were to 88.71% and 79.54%, respectively.
As the LD50 of eucalyptus and thyme essential oils were lower than the dosages of chemical insecticides and considering the phenomenon of resistance due to chemical insecticide, it seems that the herbal essential oils such as eucalyptus and thyme can be appropriate alternatives for chemical insecticides in the pest control program in the future.