| Summary: | Mosquito-borne infections are a constant problem in Vietnam, and mosquito vector control is a primary approach to control these infections. Essential oils represent environmentally friendly alternatives to synthetic pesticides for mosquito control. The essential oils of two weedy species in Vietnam, <i>Erechtites hieraciifolius</i> and <i>E. valerianifolius</i>, have been obtained by hydrodistillation and analyzed by gas chromatography⁻mass spectrometry. The essential oils have been screened for mosquito larvicidal activity against <i>Aedes albopictus</i>, <i>Ae. aegypti</i>, and <i>Culex quinquefasciatus</i>. The essential oil from the aerial parts of <i>E. hieraciifolius</i> was rich in α-pinene (14.5%), limonene (21.4%), and caryophyllene oxide (15.1%), while <i>E. valerianifolius</i> essential oil was dominated by myrcene (47.8%) and α-pinene (30.2%). Both essential oils showed good larvicidal activity against <i>Ae. albopictus</i> (24-h LC<sub>50</sub> 10.5 and 5.8 μg/mL, respectively) and <i>Ae. aegypti</i> (24-h LC<sub>50</sub> 10.6 and 12.5 μg/mL, respectively). The essential oil of <i>E. valerianifolius</i> also showed good activity against <i>Cx. quinquefasciatus</i> larvae (24-h LC<sub>50</sub> = 40.7 μg/mL). Thus, <i>Erechtites</i> essential oils may serve as low-cost vector control agents for mosquito-borne infections.
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