Study On The Attractiveness Of Different Sugar Baits And Their Volatile Compounds On Culex Pipiens Pallens

Culex pipiens pallens,a common mosquito species in Northern China,is the primary vector of lymphatic filariasis and epidemic encephalitis.Current mosquito control methods in China depend heavily on chemical insecticides to control mosquitoes,whose abusement has resulted in multifarious problems,such as environmental pollution problems and increasing insecticide resistance.Sugar feeding is a common behaviour of adult mosquitoes.Based on the sugar feeding behaviour of mosquitoes,researchers have designed the attractive toxic sugar baits(ATSB)to control mosquitoes,and it turned out to be an effective method on killing mosquitoes in the field.However,whether mosquitoes show preferences for different sugar baits remains unclear,and how mosquito adults successfully locate the sugar bait deserves further research.This dissertation investigated the preferences of Cx.pipiens pallens for different fruit-based sugar baits under laboratory and field conditions identified the volatile profiles of different sugar baits,and determined the attractiveness of synthetic compound blends to Cx.pipiens pallens adults in the olfactometer.The following results were obtained:(1)Nine common fruit species(Broussonetia papyriferae,Cucumis melo,C.melo var.saccharinms,Amygdalus persica,Pyrus bretschneideri,Malus pumila,Saccharum sinense,Prunus salicina and Ficus carica)were selected and the fruit-based sugar solutions were prepared.The attractiveness of different sugar baits to newly emerged Cx.pipiens pallens was investigated under laboratory condition.The results showed that when tested against the 5%brown sugar solution,all the sugar baits were significantly attractive to both females and males.When tested together in the mesh-covered cage,there was a significant difference on the attractiveness between different fruit-based sugar baits.The most attractive fruit species included Broussonetia papyriferae,Cucumis melo,C.melo var,saccharinus,Amygdalus persica and Pyrus bretschneideri.(2)In the field study,four fruit species(Broussonetia papyriferae,Cucumis melo,C.melo var.saccharinus and Amygdalus persica)were selected and the fruit-based sugar solutions were prepared.The attractiveness of different sugar baits to mosquitoes was investigated under field condition.The results showed that most mosquitoes that were captured were identified to be Cx.pipiens pallens in the storm drain,and Cx.pipiens pollens were still differentially attracted by the tested fruit-based sugar baits.Meanwhile,the results indicated that the mosquito population density decreased with the application of fruit-based sugar baits.(3)The volatile compounds released by the seed pods of honey melon and cantaloupe were collected by headspace solid phase microextraction,and the constituents were analyzed by gas chromatography-mass spectrometry.The results revealed that the constituents and their relative contents of the fermented fruit-based sugar baits changed when compared with those of the crude juices.(4)Based on the compound species in the volatile profiles of the crude juices and the fermented sugar baits made from honey melon and cantaloupe seed pods,the behavioural responses of female Cx.pipiens pallens to 14 kinds of compounds from the crude juices and the sugar baits were determined by Y-olfactometer under laboratory condition.The attractiveness of the synthetic compound blends with different concentrations was also determined in the same way.The results indicated that most compound species were significantly attractive to Cx.pipiens pallens females when prepared in low concentrations,and they had no attractive effect or became repellent with high concentrations.Meanwhile,the results showed that the synthetic compound blends on basis of the fermented sugar bait volatile profiles was significantly more attractive than those from the crude juices.In summary,the fruit-based sugar baits showed significantly attractiveness to Cx.pipiens pallens under laboratory and field conditions and could be potentially used in the mosquito control strategies has a wide application prospect.The attractive fruit-based sugar baits and their volatiles identified in the present study would provide necessary information and insights into developing safe,effective and environmentally friendly novel mosquito attractants.