Repellancy and contact toxicity of clove bud oil and its constituents against German cockroaches, Blatella germanica (Dictyoptera: Blattellidae), under laboratory conditions

Abstract

The German cockroach, Blattella germanica L. (Dictyoptera: Blattellidae), an invasive pest of human habitats, is distributed throughout the world, except in Antarctica. They have developed resistance against chemical pesticides used for the management of their populations. Numerous essential oils and their constituents have been tested; however, the insecticidal activities of clove bud powder, oil, and their constituents have not yet been tested against the German cockroaches. Thus, in this study, clove bud powder, oil, and their major constituents, eugenol and eugenol acetate, were evaluated for their contact toxicity and repellancy against adult German cockroaches under laboratory conditions. The clove bud powder applied at 30 mg/cm2 killed 92% of German cockroaches at 6 hours after treatment (HAT). Similarly, clove bud oil, eugenol and eugenol acetate applied at 4.00 ml/cm2 provided 95%, 85%, and 87% German cockroach mortality at 24, 6, and 24 HAT, respectively. At 2.0 ml/cm2, clove bud oil repelled 80% of German cockroaches within 30 min. In contrast, eugenol and eugenol acetate repelled 85% at 1.0 ml/cm2 and 2.5 ml/cm2, respectively, at 0.5 HAT. Based on this study, clove bud powder, oil, eugenol, and eugenol acetate could be environmentally friendly tools for the management of German cockroaches.