We evaluated the larvicidal activity of 20 plant essential oils and components from ajowan (Trachyspermum ammi) and Peru balsam (Myroxylon pereira) oils against Aedes aegypti. Of the 20 plant essential oils, ajowan and Peru balsam oils at 0.1 mg/mL exhibited 100% and 97.5% larval mortality, respectively. At this same concentration, the individual constituents, (+)-camphene, benzoic acid, thymol, carvacrol, benzyl benzonate and benzyl trans-cinnamate caused 100% mortality. The toxicity of blends of constituents identified in 2 active oils indicated that thymol and benzyl benzoate were major contributors to the larvicidal activity of the artificial blend. We also tested the acute toxicity of these 2 active oils and their major constituents against the water flea, Daphnia magna. Peru balsam oil and benzyl trans-cinnamate were the most toxic to D. magna. Two days after the treatment, residues of ajowan and Peru balsalm oils in water were 36.2% and 85.1%, respectively. Less than 50% of benzyl trans-cinnamate and thymol were detected in the water at 2 days after treatment. Our results show that the essential oils of ajowan and Peru balsam and some of their constituents have potential as botanical insecticides against Ae. aegypti mosquito larvae.

The larvicidal activities of 11 Myrtaceae essential oils and their components against Aedes aegypti were tested by the immersion method. We also tested the acute toxicity of 4 active oils and their components against the water flea, Daphnia magna. Further, the aqueous residues of these oils and their components were determined at 2 and 7 days after suspending in water. Among the 11 oils tested, 0.1 mg/mL of Melaleucalinariifolia, M. dissitiflora, M. quinquenervia, and Eucalyptus globulus oils showed strong larvicidal activity against A. aegypti. Among the test compounds, allyl isothiocyanate, γ-terpinene, p-cymene, (+)-limonene, (-)-limonene, γ-terpinene, and (E)-nerolidol showed strong larvicidal activity against A. aegypti. The acute toxicity test revealed M. linariifolia was the most toxic to D. magna. Among test compounds, allyl isothiocyanate was the most toxic to D. magna. Two days after treatment, the residues of M. dissitiflora, M. linariifolia, M. quinquenervia, and E. globulus oils in water were 55.4, 46.6, 32.4, and 14.8%, respectively. Low concentrations of allyl isothiocyanate, γ -terpinene, p-cymene, (-)-limonene, (+)-limonene, and γ-terpinene were detected in the water at 2 days after treatment. Therefore, Myrtaceae essential oils and their components could be developed as control agents against mosquito larvae.