| Aedes albopictus Skuse and Culex pipiens quinquefasciatus Say, two species of common blood-feeding mosquitoes, can transmit diseases which are seriously harmful to human health. Essential oils of plants are rich of bioactive substances and has advantages such as little harm to humaning beings and livestock, environmentally friendly, easily degradable, and little resistance to mosquitoes. Cupressaceae plants resources are heterogeneous in China, many species of the family contain various insecticidal active components. It will be great ecological and economic efficiency for developing botanical repellent insecticide using the essential oils with high-efficiency and low-toxicity sifted from cupressaceae plants.Essential oils were extracted from annual and biennial stems and leaves of five cupressacede plants [Sabina chinensis var. chinensis cv. Kaizuca, Chamaecyparis pisifera cv. Squarrosa, Sabina procumbens (Endl.) Iwata et Kusaka, Fokienia hodginsii (Dunn) Henry et Thomas and Chamaecyparis obtuse (Sieb. Et Zucc.) Endl.)] by steam distillation. Insecticidal activity of the essential oils against IV instars larvae and pupae of Ae. albopictus and Cx. quinquefasciatus was investigated by immersion method; Fumigation toxicity against adults of Ae. albopictus and Cx. quinquefasciatus at different concentration were carried out by airtight fumigation in conical flask and airtight cylinder method; Repellent activity was examined using human skin tests; The chemical components of these five essential oils were also qualitatively analyzed by gas chromatography-mass spectrometry. The results were listed as follows.The24h LC50values of essential oils from Sabina chinensis var. chinensis, Chamaecyparis pisifera, Sabina procumbens, Fokienia hodginsii and Chamaecyparis obtuse for the IV instar larvae of Ae. albopictus/Cx. quinquefasciatus by immersion method were43.99/44.06,47.66/31.74,64.84/54.11,53.21/55.85,73.11/63.94μg·mL-1respectively. And Sabina chinensis var. chinensis oil demonstrates the highest larvicide activities to Ae. Albopictus, Chamaecyparis pisifera oil demonstrates high larvicide activities to Cx. quinquefasciatus.The results of fumigation activity for adults of mosquitoes by two different methods as the follows:(1) The24h LC50values of essential oils from Sabina chinensis var. chinensis, Chamaecyparis pisifera, Sabina procumbens, Fokienia hodginsii and Chamaecyparis obtuse against adults of Ae. albopictus/Cx. quinquefasciatus by airtight fumigation in conical flask were19.44/29.08,39.35/30.46,16.77/21.68,11.99/14.32and13.79/15.63μg·cm-3respectively. And the24h LC50value of Fokienia hodginsii oil was the lowest; At the concentration of fumigation were20.82/31.24,37.99/32.57,15.73/23.59,11.32/13.59,12.95/15.54μg·cm-3, the KT50values of essential oils were8.66/6.68,8.89/6.36,9.21/7.66,9.19/8.09,7.67/7.04min.(2) The24h LC50values of essential oils from Sabina chinensis var. chinensis, Chamaecyparis pisifera, Sabina procumbens, Fokienia hodginsii and Chamaecyparis obtuse against adult of Ae. albopictus/Cx. quinquefasciatus by airtight cylinder method were3.47/2.77,5.63/3.40,3.79/1.93,3.43/3.47,4.26/3.83μg·cm-3respectively. The24h LC50value of Fokienia hodginsii oil to adult of Ae. albopictus and Sabina procumbens oil to adult of Cx. quinquefasciatus were the lowest respectively; At the concentration of fumigation were3.76/3.13,5.55/3.92,3.79/1.89,3.27/3.27,4.37/3.74μg·cm-3, the KT50values of essential oils were17.63/16.87,18.14/18.88,16.67/15.40,17.00/17.24,15.70/15.54min.Essential oils from Sabina chinensis var. chinensis, Chamaecyparis pisifera, Sabina procumbens, Fokienia hodginsii, and Chamaecyparis obtuse provide100%protection times by human skin tests were1.42/1.93,3.24/5.45,1.36/1.82,1.43/2.36,0.78/1.86h at the dosage of1.5/2.0μL·cm-2against adult of Ae. albopictus in the laboratory respectively. Chamaecyparis pisifera oil showed the longest protection time, at the dosage was2.0μL·cm-2, protection time of Chamaecyparis pisifera oil against adult of Ae. albopictus was more than10%DEET's (3.83h).Qualitative analysed chemical components of essential oils were measured by gas chromatography-mass spectrometry. Fifty five compounds were identified in essential oil of Sabina chinensis var. chinensis, including the main component a-fenchyl acetate (18.8%), followed by elemol (16.66%) and limonene (12.26%); Seventeen compounds were identified in essential oil of Chamaecyparis pisifera, including the main component a-pinene (29.89%), followed by17-norkaur-15-ene (9.96%) and△-3-carene (9.79%); Fifty eight compounds were identified in essential oil of Sabina procumbens, including the main component α-fenchyl acetate (12.49%), followed by elemol (10.46%) and t-muurolol (9.05%); Ninteen compounds were identified in essential oil of Fokienia hodginsii, including the main component α-pinene (29.25%), followed by bicyclo[2.2.1] hept-3-en-2-ol (10.88%) and caryophyllene oxide (9.64%). Twenty four compounds were identified in essential oil of Chamaecyparis obtuse, including the main component△-3-carene (35.33%), followed by α-pinene (25.60%) and β-myrcene (12.86%).The mutual compounds of essential oils was α-pinene. And many compounds of essential oils have been reported fumigataon activity and repellent activity against mosquitoes.The results show that essential oils extracted from Sabina chinensis var. chinensis, Sabina procumbens and Chamaecyparis pisifera have potential to be developed into plant mosquito larvicide; Essential oils extracted from Fokienia hodginsii and Sabina procumbens have significant fumigation activity to adults of mosquitoes, would be good sources to be developed into plant mosquitocide; The protection time to adult of Ae. Albopictus of the essential oil extracted from Chamaecyparis pisifera is the longest among the oils investigated in the study, it is concluded that Chamaecyparis pisifera oil have high potential to be developed into a plant mosquito repellent. |
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