A Novel Method For Repellency And Evaluation Of Effective Components For Solenopsis Invicta Workers

The red imported fire ant,Solenopsis invicta Buren,native to South America,is an invading pest that has posed serious harm to ecosystem,economy,and human health.Whatever children or adults suffer inflammation,itching,and tingling while being bitten by fire ants.Some people may be allergic and anaphylactic to the biting or even death comes across.In this experiment,the mosquito repellents were selected as candidates for repellency against the red imported fire ants and then were for the first time screened using digging behaviour bioassay.The composition of the best mosquito repellent(essential oil)was analyzed and identified using GC-MS technology.The walking speed and quantity of fire ant workers on the arms of Y-type repellency device were observed and recorded.The effective concentration and persistent period of better plant essential oils against fire ants were detected with the device.The main results are as follows:1 Screening of mosquito repellents against fire ant workersEleven kind of mosquito repellents were purchased in the market and their repellency to fire ant workers were tested by digging behaviour bioassay.Among them two of mosquito repellents did not show any repellent effect.The average repellent rate of six mosquito repellents reached more than 30%.One repellent formulation(active ingredient is N,NDiethyl-3-methylbenzamide)has 100% repellent rate against fire ants.2 Innovation of a Y-type repellency device and efficacy tests both indoor and in the fieldThe Y-type repellency device of five-sized arms were tested indoors.The statistical analysis showed that there was no significant difference among the number of fire ant workers walking on the different arms of Y-type device at each time period.The 11 cm Y-type device was considered as standard device for the rest of the research.If ant colony was disturbed with Y-type device,the number of fire ants climbing on the Y-type device was highest at the time of 30 s,and gradually decreased after 30 s,and then ant colony returned to quiet.The shortest time for ant colony to return quiet was 89.67 s and the longest one was203.11 s.The indoor and field experiments showed that there was no interaction between arm surface texture and time on the workers number.The field experiments showed that the number of worker ants,the calm-down period were correlated with the mound volume of fire ants on the nakedarm treatment,and calm-down period was correlated with the workers number of walking on the Y-type device.In the bandaged-arm treatment,the worker number and the calm-dowm period was also correlated with the mound volume,and the calm-down period was correlated with the cumulative number of climbing workers.3 Detection of active ingredients of mosquito repellents by GM-MS technologyThe effective components of the candidate repellent consisted of nine plant essential oils e.g.cineole,menthol,citronellal,citronellol,geraniol,nerol,terpineol,linalool and citral and2-(2-Hydroxypropan-2-yl)-5-methylcyclohexanol as well.4 Verification of essential oils’ s repellency to fire antsGC-MS analysis showed the mosquito repellent with 100% repellent rate against fire ant contained two active ingredients: the lowest content of was N,N-Diethyl-3-methylbenzamide and the highest content linalool.Once 100%,the of repellency rate the longest persistent time against workers was N,N-Diethyl-3-methylbenzamide and the shortest time is nerol.All componets with different concentrations can repel fire ants for at least 15 minutes and the repellent time of terephalin was at least 200 minutes.5 Walking speed and worker amount of fire ants on the arms of Y-type deviceThe Y-type repellent measuring ruler was used to test the climbing speed of the imported fire ants.The results showed that the climbing speed of fire ant workers was more than 2 cm/s during the periods of 15 s,30s and 45 s after disturbed,whether on bare-or bandaged-arms.The walking speed reached the maximum at 15 s and gradually decreased afterward.The highest walking speed on bare-arm was 2.76 cm / s and the lowest 1.33 cm / s;the maximum on bandaged-arm 2.46 cm / s and the minimum speed 1.15 cm / s.The results showed that whether on the bare-and bandaged-arm,the number of workers began to significantly increase at 15 s,the maximum increment in the bare-arm 16.67 at 60 s and the highest at 75 s and then gradually decreased.The maximum increment 15 in 60 s on the bandaged-arm and the highest at 75 s and started to rise or fall gradually.6 The effective concentration and persistent time of plant essential oils against fire antsThe repellency of twelve plant essential oils and chemicals to fire ants was tested using digging behavior biossay.The results showed that at the treatment of 10 mg / kg,50 mg / kg,100 mg / kg,and 150 mg / kg,11 compounds showed significantly repellent effect on fire ants compared to control.Geraniol,citral,menthol,citronellol and nerol at 10 mg / kg-150 mg /kg showed a better repellency.In addition,the repellent effects of linalool,citronellal and menthol increased with concentrations.There were no significant difference of the sand amount excavated by workers at the treatement of four concentrations of eucalyptus olein,indicating that the compound had no repellency against fire ants at all concentrations.