Insecticidal activities of the leaf oils of eight Cinnamomum species against Aedes aegypti and Aedes albopictus

The leaf oils of eight Cinnamomum species (C. rhyncophyllum Miq., C microphyllum Ridl., C. pubescens Kochummen, C. mollissimum Hook. f., C. impressicostatum Kosterm, C. scortechinii Gamb., C. sintoc B1., and C. cordatum Kosterm) were investigated for their larvicidal and adulticidal activities against Aedes aegypti (Aedes aegypti Lynn) and Aedes albopictus (Aedes albopictus Skuse). Acute mortalities of the fourth instar larvae and the adult mosquitoes were determined according to the standard WHO methods. Among the essential oils studied, the leaf oils of C. rhyncophyllum, C. microphyllum, C. pubescens, C. mollissimum, and C. impressicostatum showed significant effects against the larvae of Ae. aegypti and Ae. albopictus with concentrations that caused 50% mortality (LC50) values of less than 12.8 and 11.8 mu g ml(-1), respectively. The essential oils that showed strong larvicidal effects also demonstrated relatively strong adulticidal effects on the mosquitoes after 3 h exposure with LC50 values ranging from 133.0 to 243.0 mu g ml(-1) against Ae. aegypti and from 118.0 to 194.0 mu g ml(-1) against Ae. albopictus. The efficacy of the oils toward the larvae and adult mosquitoes of both species was nonselective as the LC50 values showed little variation. The chemical composition of the oils was investigated by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). This study suggested that the essential oils containing high levels of benzyl benzoate and benzyl salicylate exhibited strong insecticidal activities against the larvae and adult mosquitoes.