Repellent And Insecticidal Activities Of The Essential Oils From Leaves Of Eucalyptus Against Mosquitoes

The chemical composition, repellent and insecticidal activities of the essential oils from leaves of nine Eucalyptus species(Eucalyptus globulus, Eucalyptus dunnii, Eucalyptus urophyllas, Eucalyptus exserta, Eucalyptus cirtiodora, Eucalyptus camaldulensis, Eucalyptus dives, Eucalyptus pellita, Eucalyptus grandis) growing in Guangxi were investigated,and then the correlations between terpenes and repellent, insecticidal activity of nine Eucalyptus oils were annlysizdc. The main research findings are as follows:(1)The essential oils from leaves of nine Eucalyptus species (Eucalyptus globulus, Eucalyptus dunnii, Eucalyptus urophyllas, Eucalyptus exserta, Eucalyptus cirtiodora, Eucalyptus camaldulensis, Eucalyptus dives, Eucalyptus pellita, Eucalyptus grandis) were obtained by steam distillation and the volatile components were analyzed by gas chromatography-mass spectrometry(GC-MS) method.The constitutes of nine Eucalyptus oils featured a high relatively content of terpenoids, monoterpenes( 32.119%～94.575%) and sesquiterpenes(1.184%～31.920%).The principal constituents of nine Eucalyptus oils were 1,8-cineole(0.504%～61.314%) andα-pinene(0.080%～23.678%).(2)The Eucalyptus oils and their principal constituents(1,8-cineole,α-pinene,β-pine- -ne, p-cymene,α-terpineol,β-citronellal,β-citronellol) were tested for repellency against Culexpipiens quinquefasciatus accorrding to the national standard of GB/T139179.9- 2009.The nine Eucalyptus oils have repellent effects on Culex pipiens quinquefasciatus under laboratory conditions. The range of the effective protection time for human body of nine Eucalyptus oils (12.5%) was from 0 min to 60 min;The range of the effective protection time for human body of nine Eucalyptus oils (25%) was from 60 min to 330 min; The range of the effective protection time for human body of nine Eucalyptus oils (50%) was from120 min to 660 min.The essential oils from leaves of Eucalyptus globulus,Eucalyptu dunnii,Eucalyptus urophyllas, Eucalyptus dives,Eucalyptus pellita had stronger repellen activitiy to against Culex pipiens quinquefasciatus; and they have potential for the development of new and safe control products for Culex pipiens quinquefasciatus.(3)Fumigating insecticidal activity of nine Eucalyptus oils and their principal constituents (1,8-cineole,α-pinene,β-pinene, p-cymene,α-terpineol,β-citronellal,β-citronellol) were investigated by airtight fumigation in conical flask. The nine Eucalyptus oils had a high and rapid insecticidal activity on Culex pipiens quinquefasciatus. The range of half lethal concentration (LC₅₀) of Eucalyptus oils when the fumigating time was 0.5h was from 1.560% to 6.600%;The range of half death concentration (LC₅₀) of Eucalyptus oils when the fumigating was 1h was from 1.217% to 4.324%;The range of half lethal concentration (LC₅₀) of Eucalyptus oils when the fumigating was 2h was from 1.283% to 4.612%;The range of half lethal concentration (LC₅₀) of Eucalyptus oils when the fumigating was 4h was from 0.915% to 4.268%;The range of half lethal concentration (LC₅₀) of Eucalyptus oils when the fumigating was 8h was from 0.825% to 5.223%;The range of half lethal concentration (LC₅₀) of Eucalyptus oils when the fumigating was 24h was from 0.642% to 3.003%.As see from half lethal time(LT50) of Eucalyptus oils,diffent Eucalyptus oils have diffent fumigating time。the shortest fumigating time appeared in Eucalyptus cirtiodora oil(LT50=5.514min);and the longest fumigating time appeared in Eucalyptus dunnii oil (LT50=37.156min).(4)By researching the correlation between terpenes and repellent, insecticidal activity of essential oils from Eucalyptus plants,we can find that sesquiterpenes are the active components to the repellent activity in Eucalyptus oils, the effective protection time for human body increase with the increasing of the relative contents of sesquiterpenes, especially oxygenated sesquiterpenes. the longer the effective protection time for human body,the more power repellent activity of essential oils from Eucalyptus plants. The monoterpenes are active components to the insecticidal activity in Eucalyptus oils,the half lethal concentration (LC₅₀) of Eucalyptus oils decrease with the increasing of the relative contents of monoterpenes, especially oxygenated monoterpenes. the smaller half lethal concentration(LC₅₀),the more power insecticidal activity of essential oils from Eucalyptus plants,moreover,the smaller half lethal time(LT50),the shorter fumigating time.