Fumigant toxicity of essential oils fromLaurus nobilis andRosmarinus officinalis against all life stages ofTribolium confusum

Abstract

The essential oils from rosemary (Rosmarinus officinalis L.) and laurel (Laurus nobilis L.) obtained from Mersin Province in Turkey, were tested for their fumigant toxicity against all life stages of confused flour beetle (Tribolium confusum du Val.). GC-MS analysis showed that 1,8-cineole was found to be the major component of both rosemary and laurel essential oils. Vapors of rosemary and laurel essential oils were toxic to all life stages ofT. confusum. Only 65% mortality of the eggs was achieved when exposed to a dose of 172.6 mgl −1 air of rosemary essential oil at the longest exposure period (144 h); at the same dose, the pupae were the most resistant stage, with LT90 (lethal time) value of 120.2 h. The adults were the most resistant stage to laurel essential oil, with LT90 value of 77.2 h. On the basis of LT90 values, tolerance of the life stages ofT. confusum to rosemary and laurel essential oils was, in descending order: pupa < larva < adult, and larva < adult < egg < pupa, respectively. Based on the concentration × time (Ct) products (g hl −1), rosemary essential oil was more toxic than laurel to the adults and larvae ofT. confusum. However, laurel essential oil was more toxic than rosemary to the eggs and pupae. Since these essential oils need such high Ct products to obtain complete mortality ofT. confusum compared with the most commonly used commercial fumigants, it would be impossible to use them on their own as a commercial fumigant against stored-product insects.