Investigation of insecticidal properties of Rosmarinus officinalis L. and Lavandula angustifolia Mill. essential oils against German cockroach in laboratory conditions

The medical importance of the German cockroach in urban areas is increasing. Today, researchers are working to find environmentally friendly insecticides. In this study, laboratory toxicity of rosemary (Rosmarinus officinalis L.) and lavender (Lavandula angustifolia) essential oils was evaluated against German cockroaches.

The plant essential oils were obtained through hydro-distillation using a clevenger type apparatus. Then, filter papers were dipped in prepared 1.8, 6.25, 12.5, 25, 37.5, 50, 62.5 and 75 µg/m2 concentrations of mentioned essential oils and placed in the environment of male cockroaches to determine and compare their toxicity.

The results of regression probit analysis on cockroach mortality data after 24 hours showed that in both lavender and rosemary essential oils, the mortality rates of cockroaches increased with increasing essential oil concentrations. The insecticidal effect of lavender essential oil (LD50: 32.54 µg/m2) higher than rosemary essential oil (LD50: 35.97 µg/m2) that lavender essential oil exerted its insecticidal effect in a lower dose than rosemary essential oil.

Considering that the LDs50 of lavender and rosemary essential oils are much lower than current doses of chemical insecticides and due to the fact that the emergence of the phenomenon of resistance, It seems that the essential oils of plants such as lavender and rosemary can be good alternatives to chemical insecticides in the pest control program in the future.