Fumigant Toxicity of Plant Essential Oils and Selected Monoterpenoid Components against the Adult German Cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae)

The fumigant toxicity of various essential oils and selected monoterpenoid components were tested against the adult German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae). Responses varied according to plant material, concentration, and exposure time. High insecticidal activity against adult B. germanica specimens was achieved with allyl isothiocyanate (component of horseradish) and the essential oil of Allium sativum (L.) (Liliales: Liliaceae) at the concentration of 2.5 and 5 μl l of air, respectively, while the essential oils of Thymus vulgaris (L.) (Lamiales: Lamiaceae), Oregano dubium (L.) (Lamiales: Lamiaceae), Allium cepa (L.) (Liliales: Liliaceae), and Rosemarinus officinalis (L.) (Lamiales: Lamiaceae), and the monoterpenoid components eugenol, carvacrol, and citronella at the concentration of 5 μl l of air did not show any insecticidal activity. Allyl isothiocyanate at 2.5 μl l of air caused 100% mortality within 18 h, whereas over 95% mortality within 48 h was achieved with the essential oil of A. sativum at 5 μl l of air. Allyl isothiocyanate was the most toxic compound, followed by A. sativum oil. Concentrationand time-mortality tests were conducted for these 2 chemicals. Estimated LC50 and LT50 values for allyl isothiocyanate were 0.68 μl l −1 of air and 6.51 h, respectively. The findings show that allyl isothiocyanate and A. sativum had high insecticidal activity, and that they have potential as fumigants for use against the German cockroach. The essential oils and monoterpenoid components studied herein require further investigation to determine their potential as fumigants for cockroach control.