| Bemisia tabaci Gennadius(Hompptera:Aleyrodidae)is one of the most important pests in tropical,subtropical regions and adjacent temperature zone.The B-biotype of the whitefly B.tabaci had spread quickly and broke out in many areas since it invaded into china in mid.to late 1990s.It has caused severe losses to crops.Selecting pest-resistant plant strains turns out to be one of the efficient ways to control B.tabaci.At present,chemical control is still an important way to manage B.tabaci application of organic silicon can enhance the activities and reduce the dosage of insecticides in large scale.It is important for the reasonably and efficiently utilization for pesticides against this pest.In this thesis,laboratory experiments were carded out to investigate selectivity and fitness to twelve varieties of eggplant Solanum melongena Linn,toxicity of pesticides mixed with organic silicon to B type B.tabaci and it's parasite Encarsia formosa(Gahan),with the purpose of providing scientific information for application of pest-resistant varieties of eggplant,and for the reasonably and efficiently utilization of pesticides to manage B-type B.tabaci.The results of the experiments were summarized as follows:(1)Selectivity and oviposition preference of B-biotype B.tabaci were significantly different among the twelve tested varieties of eggplant.B.tabaci preferred Heishanhu,No.lYinqie,Heijin to No.lHangqie,Xiaoshanbaiqie,Yeshengqie,No.2Guanwang,it had least preference for Bengbuqingchangqie,Moqie,Sairuima,Tongfenghongqie.(2)There were significant differences in survival rate,development duration,longevity and female fecundity of B-biotype B.tabaci among the twelve tested varieties of eggplant.The development duration of B-biotype B.tabaci from egg to adult is longest(21.29days)on the Yeshengqie whereas it was shortest on Fangchengqingqie(18.19 days).The survival rate was high in every stars of B.tabaci,from egg to adult,the survival rate is highest on Heishanhu,and No.1Yinqie-, lowest on Yeshengqie,B.tabaci had the most fitness,longest adult longevity and higher female fecundity on Heishanhu,No.1 Yinqie,whereas it had the poorest fitness,the shortest adult longevity and the least fecundity on Moqie,Tongfenghongqie,suggesting that Moqie and Tongfenghongqie can be used as pest-resistant cultivars.(3)The toxicity of five insecticides mixed with organic silicon on the egg,nymph,adult stages were evaluated using leaf dip method under laboratory conditions.Generally speaking,the toxicity order of tested insecticides against the egg stage was as follows:cyhalothrin＞acetamiprid＞pyriproxyfen＞pymetrozine＞azadirachtin;the toxicity order of tested insecticides against the younger(first and second nymphal instars)nymph stage was:acetamiprid＞pyriproxyfen＞pymetrozine＞azadirachtin＞cyhalothrin;the toxicity order of tested insecticides against the older (third and fourth nymphal instars)nymph stage was:acetamiprid＞azadirachtin＞cyhalothrin＞ pyriproxyfen＞pymetrozine.After there days adult exposure to the pesticides,the toxicity order of tested insecticides against the adult stage was:acetamiprid＞azadirachtin＞pymetrozine＞pyriproxyfen＞cyhalothrin,the toxicity of acetamiprid was highest,it could produce 100%mortality of adults.When the pesticide mixed with the organic silicon,silicon could effectively influence the toxicity of the pesticides,organic silicon showed effectively synergism for acetamiprid against any star of B. tabaci,even low concentration acetamiprid mixed with organic silicon,it also had high toxicity to B. tabaci,when organic silicon mixed with azadirachtin,the mixture showed high toxicity to the egg star of B.tabaci,the mixture of silicon and pymetrozine showed high toxicity to the older nymph and adult star of B.tabaci,organic silicon showed no synergistic effect to two other pesticides.Applying organic silicon as synergists,it not only enhances the activities of pesticides but also enhance the penetrability of acetamiprid and pyriproxyfen.(4)The adults of B-type B.tabaci,which had exposed to pyriproxyfen coated on eggplant leaves for 2 days,laid significant more eggs than those that had not exposed to pyriproxyfen,and the eggs laid by the former gave significant lower hating percentage than those laid by the latter.The mixture of pyriproxyfen and silicon could effectively decrease hating percentage of eggs.(5)Encarsia Formosa(Gahan)is an important natural enemy of B.tabaci,it has widely and successfully used for biological control in greenhouse.The toxicity order of five pesticides to the pupae of E.formosar was:cyhalothrin＞acetamiprid＞azadirachtin＞pyriproxyfen＞pymetrozine.When acetamiprid,cyhalothrin,pymetrozine,pyriproxyfen mixed with organic silicon respectively,there was no different toxicity to the pupae between the mixture and that four kinds of pesticides without silicon,but the toxicity of azadirachtin mixed with silicon was higher than the azadirachtin only.
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