Field Monitoring Of Two Thrips And Effects Of Tomato Spotted Wilt Orthotospovirus On The Fecundity Of Frankliniella Occidentalis(Pergande)

Western flower thrips(WFT),Frankliniella occidentalis(Pergande)and onion thrips,Thrips tabaci(Lindeman)are wideworld vegetable and ornamental pests,incurring damage directly,by rasping plants organs,and indirectly,by spread a variety of plant virus,such as Tomato Spotted Wilt Orthotospovirus(TSWV),then causing significant yield loss to crop production.In order to clarify the occurrence and prevalence features of WFT and TSWV in the field and the TSWV impact on the fecundity of WFT,screened insecticides with high efficacy and low toxicity to control T.tabaci.In this study,we used conventional PCR to ’detect the carrying virues rates of WFT in different geographic groups.We investigated the occurrence characteristics of TSWV and WFT in greenhouse pepper.We studied the TSWV impact on the fecundity of WFT.The toxicity and control effect of different insecticides on T.tabaci was evaluated via laboratory and field experiments.The main results were as follow:1.Testing the carrying viruses rates of WFT in different geographical groupsWe used conventional PCR to detect the carrying virues rates of WFT in 9 geographical groups.The results showed that the carrying viruses rates of WFT collected from greenhouse pepper in Yuanmou of Yunnan,Zhangjiakou of Hebei and Yanqing of Beijing were 85%,10%and 5%,respectively.However,the carrying viruses rates of WFT collected from greenhouse pepper in Changping District of Beijing,greenhouse cucumber in Urumqi of Xinjiang,and Huairou District of Beijing,field vetch in Songming County of Yunnan province and field cabbage in Shangsuan County of Yunnan province.2.Investigating the occurrence features of WFT and TSWV in greenhouse pepperWe investigated the occurrence features of WFT and TSWV in greenhouse pepper.The results showed that the occurrence of TSWV was closely related to the population density of WFT.The initial incidence of TSWV in pepper in spring and autumn were 20%.The incidence of TSWV in pepper in spring reached peak over 90%in early May,meanwhile,the population density and the carrying viruses rates of WFT also reached respectively their peak with 1.4 individuals per plant and carrying viruses rates 100%.The incidence of TSWV in pepper in autumn increased slowly,and with a peak of 45%,the population density and the carrying viruses rates of WFT were respectively 3.1 individuals per plant 27.8%.The results further showed that the incidence of TSWV in solar greenhouse pepper in spring was significantly higher than that in autumn.3.Detecting the occurrence of TSWV in different organs of pepperWe detected the occurrence of TSWV in leaves,petals,stamens,fruits and seeds of the pepper.The results showed that the incidence of TSWV in the leaves,petals,stamens,fruits and seeds of the pepper were 100%,90%,70%,100%and 86.67%,respectively.The seeds were stored at room temperature for 60 d,the carrying viruses rates of TSWV in them were 88.64%(selected randomly and detected respectively).Then,the seeds were seeded,and the carrying viruses rates of TSWV in pepper which grown to cotyladom and initial anthesis stage were respectively 0%.The results further showed that TSWV was a kind of systematic infection virus which could infect all kinds of the organs in pepper,but the seeds could not transmit TSWV.4.Clarifying the TSWV impact on the fecundity of WFTWe collected the first instar nymph of WFT which hatched within 6 h,and puted them in TSWV-infected Datura stramonium leaves for feeding,after 3 h,transferred them to health kidney bean leaves for raising.When TSWV-exposed and unexposed WFT emerged,the adults were paired(one female and one male)and contained with heath kidney bean.The total number and the sex ratio of their offspring were recorded.A total of four cross-pairing treatments were designed as follows:treatment 1:F(-)× M(-);Treatment 2:F(-)×M(+);Treatment 3:F(+)×M(+);Treatment 4:F(+)×M(-).The results showed that the carrying viruses rates of WFT was 61.11%after exposed for 3 h in TSWV-infected Datura stramonium leaves.The highest and the lowest TSWV-exposed level of WFT were respectively 3 and 1,which respectively account for 6.02%and 49.62%of the total number of the parental generation.TSWV had no significant impaction on the total number of F1 generation.However,when female of parental generation was TSWV-exposed and on matter whether the paired-male was TSWV-exposed or not,the total number of males of F1 generation were greater than that of the females.The female/male ratio of F1 generation shifted from 2.10-2.68/1 to 0.53-0.55/1.The TSWV-exposed level had no significant impaction on the total number of F1 generation which the TSWV-exposed level 3 was respectively greater than that of the TSWV-exposed level was 1 and 2.5.Sceening insecticides with high prevention effect on onion thripsThe lethal concentration(LC50)of 8 kinds of insecticides and 9 kinds of insecticides on the adult and nymphal of T.tabaciwere determined by indoor virulence and field control experiments.Laboratory bioassay showed that abamectin,spinetoram and clorfenapyr had the highest toxicity to adults,with their LC50 values below 1 mg/L,and followed by spinosad with the LC50 value was 2.11 mg/L.Pyriproxyfen had high toxicity to the 2nd instar nymphs of T.tabaci.Filed trial showed that the lambda cyhalothrin,chlorfenapyr and spinetoram had strong rapidness and persistence to T.tabaci,the control efficacies of all above were over 90%after 3 d to 14 d post spraying.The rapidness of abamectin,broflanilide and emamectin benzoate was strong.The control effect reached more than 92%after 3 days,but the holding effect gradually decreased.The control effect on 14 d were 88.51%,87.60%and 82.31%,respectively.The rapidness of Spinosad and thiamethoxam was low,but the control effect increased gradually with the extension of time,and the control effect of 14 d after the drug reached more than 88%.The rapidness of pyriproxyfenin the control of nymphal fumarate was good,and the control efficiency was 86.83%after treatment 3 d.However,the holding efficiency of pyriproxyfen was poor,and the control efficiency of treatment after 14 d was 58.51%.As a result,lambda cyhalothrin,clorfenapyr and spinetoram could be the product insecticides to control T.tabaci,and the insectcides could be used alternately.