Mosquitoes are vectors of many human diseases such as Japanese encephalitis, vivax malaria, west nile fever, dengue fever and yellow fever. However, factors affecting the abundance and distribution of mosquitoes are not well-understood. Moreover, the global climate change makes it even more difficult to address and predict the population dynamics of mosquitoes. Therefore, it is important to monitor this medically-important pest throughout landscapes over a long period of time. This study was conducted as a part of the nation-wide surveillance program to monitor insect vectors. In 2015, mosquitoes were collected using black light traps and BG-Sentinel traps in Gyeonggi-do at every two weeks from April to September. Three types of potential mosquito habitats were selected for surveillance: urban area (Suwon), cattle shed (Yongin) and wild bird refuge (Gwangju). Among the three habitats, female mosquitoes were first caught on April 4 by BG-Sentinel trap in the urban area. The highest density of female mosquitoes in the traps was recorded in July in the urban area (134 ± 84 per trap); the highest density was observed in June in the cattle shed (2473 ± 1319) and wild bird refuge (21 ± 15) (mean ± SE). The dominant mosquito species were Culex pipens pallens (91%), Aedes vexans nipponii (79%) and Anopheles sinensis (33%) in the urban area, cattle shed and wild bird refuge, respectively. The results of this study indicate that female mosquitoes were most abundant in the cattle shed habitat type. It is also noteworthy that the dominant mosquito species varied among the habitat types surveyed. This nation-wide monitoring program for medical pests will provide fundamental basis to develop effective management strategy under the global climate change environment.

We examined the adulticidal activity of 34 plant essential oils when they were sprayed on female Culex pipiens pallens adults. At concentrations of 1000 ppm, four oils, namely, cardamon, coriander, rosemary, and sandalwood, had adulticidal activities ranging from 67.8% to 98%. Sandalwood oil had the highest adulticidal activity with an LC50 value of 445ppm. Gas chromatographic (GC) and GC-mass spectrometric analyses revealed that the major constituents of cardamon were 1,8-cineole, α-terpinolene and α-terpinene; those of coriander were γ-terpinene, camphor, linalool and geranyl acetate; those of rosemary were β-pinene, 1,8-cineol, camphor and linalool; and those of sandalwood were α-santalol (69.4%) and β-santalol (15.3%). Both of the major components of sandalwood had the highest adulticidal activity of all the monoterpenes tested. When inhibitors of enzymes known to promote insecticide resistance were mixed with each of the four essential oils, a synergistic effect was only observed when sandalwood was mixed with 100 ppm PBO, which enhanced the adulticidal activity of 500 ppm sandalwood from 41% to 90%.