Larvicidal Effect of Spearmint (Mentha spicata) and Rosemary (Rosmarinus officinalis) against Larvae of Culex

Mosquitoes are vectors or intermediate hosts for several infectious microorganisms worldwide. Due to harmful effects on the environment, high operating costs, as well as the resistance of mosquitoes to chemical insecticides, the need for biological control of mosquitoes has been considered by researchers. In the present study, the larvicidal effect of essential oil of spearmint (Mentha spicata) and rosemary (Rosmarinus officinalis) against larvae of Culex was investigated.

From May to September 2018 a total of 1,200 larvae of Culex mosquitoes were caught from four areas of Qarachai river located in Khondab city of Markazi province. The larvae were encountered to concentrations of 10, 50, 200 and 600 ppm aqueous solution of spearmint and rosemary essential oils produced by Barij Essence Pharmaceutical Company. Larval mortality was assessed at 6, 12, 24, 48 and 72 hours after exposure to the tested materials. The experiment was repeated three times and for each concentration, the average number of killed larvae was calculated. For negative control distilled water and for positive control 1 ppm cocentration of organophosphate larvicide “Temephose” were prepared and tested.

Although all concentrations of spearmint and rosemary essential oils at different timepoints showed some degree of effect on the larvaa, spearmint essential oil at 200 ppm and at 6 hours, showed the fastest and highest larvical effect.

The present study showed that both essential oils, especially spearmint, could be considered as a potential alternative to chemical insecticides for biological control of Culex mosquito larvae.