Studies On Bioactivities Of Thrity Six Essential Oils Against Two Mosquitoes

Mosquitoes affect human life and healthy.The main measure to prevent and control mosquitoes is the chemical pesticides.However,a series of adverse effects are produced for the long-term,large and irrational use of chemical synthetic insecticides,causing public concern.Therefore,people are trying to find safe and environmentally-friendly insecticides instead of chemical synthetic insecticides.Essential oils are low toxic,low residue,and exhibit high bioactivity against mosquitoes,which meet the requirements of environmentally-friendly insecticides.At present,most of the researches on the bioactivity of essential oils against mosquitoes are in the stage of laboratory research,there are few products in the practice of mosquito control.In view of this,this paper on the basis of previous research,the domestic common Culex pipiens pallens and Aedes albopictus are selected as the research object,evaluation of the 36 essential oils fumigation activity against C.pipiens pallens and repellent activity against A.albopictus.Initially,2 plant source mosquito control agents has a certain developed application value are found.The main results are shown as follows:（1）The fumigation activity of thirty-six essential oils against C.pipiens pallens adults was evaluated by airtight fumigation in sealed conical flasks or hermetic round canisters.The results of fumigation assay in sealed flasks showed that 10 essential oils including Pinus massoniana leaf oil,Magnolia oil and red moor besom leaf and so on,possessed high toxicity against C.pipiens pallens adults with low KT₅₀values（<10 min）at 12μL/L,and P.massoniana leaf oil exhibited the highest fumigation activity with the KT₅₀ value of 3.40 min.The fumigation of red moor besom leaf oil and grapefruit oil caused higher mortality rates at24 h after treatment,with the LC₅₀values of 0.95 and 1.11μL/L,respectively.The results of fumigation assay in hermetic round canisters revealed that the KT₅₀ value of P.massoniana leaf oil against C.pipiens pallens adults was 13.79 min at the concentration of 12μL/L,and the mortality rate of C.pipiens pallens adults caused by Red moor besom leaf oil at the concentration of 1.67μL/L was 100%.（2）The repellent activity of 36 essential oils against Aedes albopictus was evaluated by Y olfactometer.The amount of essential oil in 5μL,Blumea balsamifera oil,Thyme aetherolea oil and Forsythia oil and other 7 essential oils exhibited good repellent activity,the repellent rate more than 80%within 5 min,the B.balsamifera oil has the best effect,the rate is 100%within 20min.When the amount of essential oil 2μL,Blumea balsamifera oil,Thyme aetherolea oil and Forsythia oil still showed good repellent activity,the repellent rate is still above 80%within 5min,B.balsamifera oil repellent rate above 80%within 15 min,followed by Thyme aetherolea oil and Forsythia oil.According to the national standard GB/T 13917.9-2009verification shows that the effective protection time of B.balsamifera oil up to 90 min.（3）The main ingredients of P.massoniana leaf oil,Red moor besom leaf oil,B.balsamifera oil,Thyme aetherolea oil and Forsythia oil analyzed by GC/MS.P.massoniana leaf oil were detected 10 compounds,theρ-cymene was the highest,the content was 65.14%,followed byβ-pinene（7.54%）;Red moor besom leaf oil were detected 22 compounds,the highest content is 3-carene（42.12%）;The B.balsamifera oil were detected 24 main compounds,diacetone alcohol was the highest relative content is 11.74%,followed by eucalyptol（8.5%）,ocimene（6.6%）,bornyl acetate（6.2%）andα-pinene（5.25%）;Thyme aetherolea oil were detected 19main compounds,the highest component is thymol（35.58%）,followed by diacetone alcohol（10.06%）;Forsythia oil were detected 5 main compounds,3-carene content was the highest,the content is 75.59%,followed by diacetone alcohol（17.37%）and camphene（4.19%）etc..（4）The airtight fumigation in sealed conical flasks method determined fumigation activities of P.massoniana leaf oil and Red moor besom leaf oil with single and mixed pairs aganist C.pipiens pallens.the results showed when P.massoniana leaf oil and Red moor besom leaf oil volume ratio is 1:9,when mixed oil is 0.5μL,the KT₅₀ was 16.27 min and 24 h mortality rate was 100%against C.pipiens pallens,with the LC₅₀values of 1.33μL/L.It has the development potential of plant source fumigant mosquitoes.According to the national standard GB/T 13917.9-2009 valued repellent activity of B.balsamifera oil and Thyme aetherolea oil alone and mixed against A.albopictus.The results showed that mixed oil repellent effect were better than single oil,the effective protection time was 120 min.Through screen on oil formulation,found that a formula as”21%B.balsamifera oil+9%Thyme aetherolea oil+5%tween80+synergistic agent S₁”repellent effect on the human body was the best,the protection time up to 4 h,reached the national standard B.Therefore,B.balsamifera oil and Thyme aetherolea oil has potential of developed agent repellent mosquito.