Study On Insecticidal And Repellent Activity Of Five Essential Oils Against Culex Pipiens Quinquefasciatus And Aedes Albopictus

Mosquitoes are blood-feeding insects, which transmit many diseases, such as malaria, filariasis, Japanese encephalitis and dengue fever. It is the most important public health problem in wide areas. Many methods and materials have been using to control mosquitoes. One of the better materials is the chemical insecticides, which control activity is good and continuing time is very long. The chemical insecticide was the most important to control the mosquito-borne diseases at special areas in past, and also can't replace by else in our daily life. But the level of insecticide resistance was higher and higher, and the hazard effect on the environment was harder and harder, induced by the extensive and long time usages of synthetic chemical insecticides during the last five decades. It is necessary to search and develop on the new insecticides with environment safely, biodegrading easily, lower cost and choosy toxicity.Essential oils and their components are products chemicals from the secondary metabolism of the plants. Generally, essential oils consist of hydrocarbons or monofunctional compounds from mono- and sesqui-terpenes, together phenylpropanoids and other volatile aliphatic and aromatic substances. Essential oils extracted by steam distillation from plants. They can easily dissolve by ethanol and aether, but difficultly by water. As known many essential oils have insecticidal and repellent activity. For the pleasant odor of essential oils, it is promising for them to be applied for mosquito control and for us to find natural template of artificial chemicals. Therefore, studies on essential oils have ecological, social and economic potential for exploitation.In this study deals with the investigation of five essential oils, their adulticidal and repellent effects against Culex pipiens quinquefasciatus and Aedes albopictus. the chemical components of the most effective essential oil, adulicidalactivity of the major component against Cx. pipiens quinquefasciatus and to discuss the five essential oils' mechanism against Cx. pipiens quinquefasciatus.The result is as the follows:1. The five essential oils have toxic effects on Cx. pipiens quinquefasciatus under laboratory conditions. The most effective essential oil was Rutaceae oil.2.7% five essential oils have repellent activity of Ae. albopictus to protect Kunming mouse. Carvacryl oil was the best repellent which gave protection against Ae. albopictus for at least 7h. Citronella oil repelled at an average of 94% after 8h treated. The protection time of Rutaceae oil and Asteraceae oil against Ae. albopictus are correlative with the concentration.3.To study the change of acetylcholinesterase(AchE) and non-specific esterase(NSE) activity of the five treated groups, provide scientific basis for the five essential oils' mechanism against Cx. pipiens quinquefasciatus, the result indicated that AchE was the main target enzyme of Carvacryl oil and Citronella oil. NSE was the target enzyme of Rutaceae oil, Carvacryl oil Citronella oil and Mentha piperita oil.4.The chemical components of Rutaceae oil were analyzed by GC-MS technique. Fifty-five components were identified. A and B were the major components (69%). A showed a marked mosquito adulticidal activity against Cx. pipiens quinquefasciatus at short-term fumigation. But Rutaceae oil showed highly toxic effects on mosquito adults at long-term. The result indicated that the msecticidal effect of Rutaceae oil was the combination of many components.