Toxicities of 10 insecticides were examined against late third instars of Culex tritaeniorhynchus using the direct-contact mortality bioassay. Six geospatially distant field mosquitoes were collected from Chuncheon-si (designated CC-CT), Hwaseong (HS-CT), Seosan (SS-CT) Jeonju (JJ-CT), Daegu (DG-CT), and Busan (BS-CT) in the Republic of Korea (ROK). Marked regional variations of insecticide susceptibility were observed. Field populations of SS-CT, JJ-CT and DG-CT from agricultural areas showed higher to extremely higher insecticide susceptibility to pyrethroids than those of CC-CT, HS-CT and BS-CT strains from none agricultural areas. Extremely high to low levels of susceptibility were measured: bifenthrin, susceptible ratio (SR) = 2.7–896.3; β-cyfluthrin, SR = 1.8–633.3; α-cypermethrin, SR = 1.2–1,051.9; deltamethrin, SR = 1.3–711.1; permethrin, SR = 1.5–1,053.4 etofenprox, SR = 2.2–29.3; chlorfenapyr, SR = 5.1–103.6; chlorpyrifos, SR = 2.3–337.0; fenitrothion, SR = 2.0–142.3 and fenthion, SR = 1.4–186.2. Culex tritaeniorhynchus populations from rice paddies had been under heavy selection pressure due to the agricultural insecticides and that’s why the mosquito species demonstrated high resistance to pyrethroids which were used for a long time to control agricultural pests in the localities. These results indicate that careful selection and rotational use of these insecticides mayresult in continued satisfactory control against field populations of Japanese encephalitis vector mosquitoes.

The volatile flavor compounds of Saussurea lappa C.B. Clarke, a perennial, aromatic and medicinal herbaceous plant of the Asteraceae family, were isolated by the hydro distillation extraction method using a Clevenger-type apparatus, and analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). The plant yielded a light yellow colored oil (0.02%, v/w). From S. lappa C.B. Clarke root oil, sixty-three volatile flavor compounds were tentatively identified, among which sesquiterpene was predominant (2 1.70%). The identified compounds of the root oil constituted 87 .47% of the total peak area. From the constituents making up more than 5% of the volatile flavor components, a long-chain aldehyde, (7Z, 10Z, 13Z)-7, 1 0, 13-hexadecatrienal, was the most abundant volatile flavor compound (2 1.20%), followed by dehydrocostuslactone (10 .30%) belonging to sesquiterpene lactone, valerenol (5.30%) and vulgarol B (5.06%).