Young-Su Jang

Mosquito larvicidal activity of active constituent derived from Chamaecyparis obtusa leaves against 3 mosquito species.

ABSTRACT Mosqutio larvicidal activity of Chamaecyparis obtusa leaf-derived materials against the 4th-stage larvae of Aedes aegypti (L.), Ochlerotatus togoi (Theobald), and Culex pipiens pallens (Coquillett) was examined in the laboratory. A crude methanol extract of C. obtusa leaves was found to be active (percent mortality rough) against the 3 species larvae; the hexane fraction of the methanol extract showed a strong larvicidal activity (100% mortality) at 100 ppm. The bioactive component in the C. obtusa leaf extract was characterized as β-thujaplicin by spectroscopic analyses. The LC50 value of β-thujaplicin was 2.91, 2.60, and 1.33 ppm against Ae. aegypti, Oc. togoi, and Cx. pipiens pallens larvae. This naturally occurring C. obtusa leaves–derived compound merits further study as a potential mosquito larval control agent or lead compound.

Larvicidal Activity of Australian and Mexican Plant Extracts Against Aedes aegypti and Culex pipiens pallens (Diptera: Culicidae)

Abstract Larvicidal activity of methanol extracts of 22 Australian and 12 Mexican plants against early 4th-instar larvae of Aedes aegypti and Culex pipiens pallens was examined. At 200 ppm, 100% mortality in larvae of A. aegypti and C. pipiens pallens was obtained in extracts of Kigelia pinnata and Ruta chalepensis. The extract of K. pinnata gave 76.3 and 80.3% mortalities in larvae of A. aegypti and C. pipiens pallens at 100 ppm but, at 50 ppm, 23.7 and 42.1% mortality against larvae of A. aegypti and C. pipiens pallens , respectively. The extract of R. chalepensis gave 81.2 and 87.9% mortality in larvae of A. aegypti and C. pipiens pallens at 100 ppm but 23.4 and 53.3% mortality against larvae of A. aegypti and C. pipiens pallens at 50 ppm, respectively. Larvicidal activities of K. pinnata and R. chalepensis extracts were significantly reduced when used at 25 ppm. Consequently, further studies of these plants as possible agents for mosquito control are warranted.