Fumigant Toxicity of Essential Oils From Five Officinal Plants Against Two Stored Product Insects: Cowpea Weevil, Callosobruchus maculatus (Fabricius) and Red Flour Beetle, Tribolium castaneum (Herbest)

Fumigant toxicity of various doses of essential oils (185.2, 370.4, 555.5, 740.7, 925.4, 1111.1, and 1296.3 µl/l water) from five officinal plants, including rosemary (Rosmarinus officinalis), lavender (Lavandula vera), fennel (Foeniculum vulgare), tarragon (Artemisia dracunculus)and summer savory (Satureja hortensis)on two stored products pests, cowpea weevil (Callosobruchus maculatus) and red flour beetle (Tribolium castaneum) have been studied. The cowpea weevil was more susceptible than red flower beetle for all essential oils have been tested. The essential oil of rosemary showed the most fumigant toxicity among the tested plants so that mortality of cowpea weevil in treatment with the least dose of related essential oil reached 100% after 12 h. The mortality of red flower beetle was 5% at the same time; however, after 24 h it reached 30%. The essential oil of tarragon that showed the least fumigant toxicity caused 100% mortality in cowpea weevil after 18 h and 95% mortality in red flower beetle after 24 h. The mortality of cowpea weevil in treatments with high doses of essential oils from lavender, fennel and summer savory after 5, 18 and 18 h reached 100%, respectively. This time was 24 h for the red flower beetle, treated with mentioned treatments. The LT₅₀ calculated for cowpea weevil and red flower beetle in treatment with lavender essential oil were 24.96 and 4.78, that of rosemary 30.14 and 11.73, of fennel 15.64 and 8.71, of  tarragon 11.74 and 6.10 and essential oil of summer savor were 12.28 and 3.60 h, respectively.