Selection Of Botanical Insecticides Against Pomegranate Aphids In Bengbu Area And Their Field Control Effects

Pomegranate cultivation in Bengbu area of Anhui province has a long history and pomegranates have been sold overseas for its gorgeous colors and crystal-clear fruits.However,pomegranate aphids are the most important pests of pomegranate from germination to stable fruiting stage,which reduces fruit setting rate and affects pomegranate yield severely.At present,chemical pesticides are used widely for controlling pomegranate aphids,which seriously destroy the environment and causing potential harm to human health,restricted the process of building“green food”in the Bengbu area.In date,lots of researchers focused on the biological control agents,which have been used to instead chemical pesticides for pest control.However,systematic studies on biological control agents for controlling pomegranate aphid have not been reported.Therefore,different botanical pesticides were used to control pomegranate aphids in the Bengbu area.In this study,we got the most suitable botanical pesticide for controlling pomegranate aphids in Bengbu area,with serval biocontrol assays（indoor toxicity and field efficacy test）were performed with nine kinds of botanical pesticides on different instar larvae of pomegranate aphids,which provides the basis for botanical pesticide application in Bengbu area.The main results are as follows:1.Indoor toxicity test:Firstly,nine botanical pesticides were prepared with the concentration as the instructions recommended.And indoor toxicity test of different botanical pesticides was performed.According to the data obtained from the test,eight botanical pesticides（tea saponin excepted）showed a significant effect on the control of pomegranate aphids after 24 h treated.Of which,pyrethrin,rotenone and nicotine revealed great toxicity on the pest,and the corrected mortality rates are moreover than 70%;matrine and cineole showed good toxicity on the pest,and the corrected mortality rates are 54%and 45%;the corrected mortality rates of emamectin,avermectin,azadirachtin EC and are under 40%.Five botanical pesticides（pyrethrin,rotenone,nicotine,matrine and cineole）,the corrected mortality rates are more over than 40%,were used for further toxicity test with different concentrations.The data reveled that nicotine at the 50000mg/L concentration showed good effect on the pest toxicity,which the corrected mortality rate is over 90%on the third day of the test;rotenone showed the strongest toxicity at 120mg/L concentration at the third day,which the corrected mortality rate is over 92%;pyrethrin showed the strongest toxicity at or more than 60mg/L concentration at the fifth day,which the corrected mortality rate is nearly 92%;cineole showed the strongest toxicity at 50mg/L concentration,the corrected mortality rate is less than 60%,which the virulence is relatively weak;matrine showed the strongest toxicity at or more than 300mg/L concentration,the corrected mortality rate is 65%.Based on the results mentioned above,the virulence order:pyrethrin,rotenone,nicotine>matrine>cineole.Based on the virulence order,we choose rotenone,pyrethrin,and nicotine to determine these botanical pesticide toxicities under different temperatures and humility.The data showed that both temperature and humidity had an obvious influence on the insecticidal effect of these three pesticides,and three pesticides were most effective in controlling pomegranate aphids under 80%humidity and 25^?C.Furthermore,these botanical pesticides toxicity on different instar larvae(2nd,3^rd,and 4th)of pomegranate aphids was detected.Pyrethrin showed the best control effect for 2nd,3rd and 4th instar larvae,among the three insecticides used.Following the pyrethrin,rotenone showed the strongest toxicity,although nicotine revealed more stronger toxicity than rotenone within three days,rotenone showed better toxicity than nicotine at the third day,which suggested rotenone showed better control effect on pomegranate aphids than nicotine.Field efficacy test:The change of the outdoor environment will directly affect the insecticidal effect of botanical pesticides.Therefore,we choose two botanical pesticides（pyrethrin and rotenone）for field efficacy tests,and chemical pesticide（Imidacloprid）was used as control.In order to ensure the virulence effect for pomegranate aphid in the whole Bengbu area,we performed field efficacy test in Huaiyuan,Wuhe and Guzhen area,respectively.Pyrethrin showed the strongest toxicity at or more than 60mg/L concentration,and the dropping rate of insects is 42%on the first day,more than 48%on the third day,and more than 60%after seventh day.Rotenone showed the strongest toxicity at 120mg/L concentration,and the dropping rate of insect is over 36%at the first day,nearly 60%between the third and seventh days.Combined with the data from indoor toxicity and field efficacy test,pyrethrin（60mg/L）showed the strongest toxicity among all nine tested botanical pesticides.