| Hemiptera pest is the greatest species,largest abundance,and heaviest pest group in rice region ecosystem of China.Rice planthopper is the most important pest group threatening rice production among the Hemiptera pest,which accounts for more than1/3 of the area yearly.Over a long period,the major measurement against rice pests in China has mainly relayed on chemical pesticides.The “3R”(Residue、Resistance and Resurgence)caused by the chemical pesticides is more and more serious.Therefore,the application of sustainable,environmentally friendly and ecological based control strategies has become an urgent need.Parasitic wasps,the most common natural enemies in the paddy field,are important factors to control the rice pests.At present,the systematic records of parasitic wasps in rice fields of China were mostly conducted during 1970s-1980 s.However,with the rapid development of China,the mode of agricultural production and the ecological environment of rice field have been changed greatly,which has deeply affected the parasitic wasp community in rice field consequently.Therefore,re-investigating the diversity of parasitic wasps in rice fields,accurately identify the species of parasitic wasps,ascertaining the occurrence of major species,studying the biological characteristics of important species,and evaluating the application potential of parasitoids are important aspects for using of parasitic wasps to control rice pests.In view of the above points,this study carried out the inventory of parasitic wasps of hemiptera pests and understand the community structure of parasitic wasps and the occurrence of dominant populations in Chinese rice region,build a digital image and DNA barcode database for identifying common species and study on the biological traits of an important parasitic wasp of rice planthopper-Gonatopus flavifemur(Esaki & Hashimoto).The results are as follows:1.Diversity and species description of parasitic wasps on Hemiptera pestsFifteen provinces in southern China was involved and more than 33,600 specimen were identified.118 species were collected,including 16 new species and7 new record species in China.There are 109 species of primary parasitic wasps,namely 9 species of Trichogrammidae,31 species of Mymaridae,3species of Eulophidae,4species of Pteromalidae,16 species of Encyrtidae,10 species of Aphelinidae,1 species of Signiphoridae,7 species of Aphidiinae,7 species of Scelionidae,21 species of Dryinidae.9 species are hyperparasitic wasps,including 2species of Encyrtidae,1 species of Pteromalidae,1 species of Eurytomidae,3 species of Ceraphronidae,2 species of Megaspilidae.Compared with previous studies,there were 45 species of primary parasitic wasps added on the list.The total species were almost doubled.At the same time,the distribution range either inside and outside China,host information,collecting methods of each species were summarized in systematic way.In addition,a new taxonomic key of parasitic wasps was compiled by focusing on the southern China.More than 380 high-resolution images of wasps were obtained by using the extended depth of focus(EDF)system and digital software.The high resolution primary color photographs of Mymaridae,the smallest parasitic wasps in rice fields,have been taken for the first time in China.2.Study on DNA barcoding of common dryinids in rice regionThe partial 16 Sr DNA,COI and Cytb gene sequence of 16 species,representing 5subfamilies and 7 genera,were sampled in this study.Comparison and analysis of gene sequence characteristic,genetic distance on different taxonomic levels and phylogenetic information,the Cytb gene sequence was further verified to be a DNA barcode suitable for the identification of dryinids species in rice field,the DNA barcode database was constructed.Based on the Cytb gene,the phylogenetic relationship of these Dryinids has been constructed.The results showed that Anteoninae,and Conganteoninae are sister group,this sister group and Gonatopodinae,Dryininae formed a larger monophyletic group,Aphelopinae was a monophyletic group.In addition,the specific molecular marker primers were designed on Cytb gene for rapid molecular identification of five species of dryinids,including G.flavifemur,G.nigricans,Haplogonatopus apicalis,H.oratorius and Echthrodelphax fairchildii,that solved the problem of species identification in nymphal stage.3.Community structure and occurrence of parasitic wasps of Hemiptera pests and rice planthopperThe parasitic wasp communities in 10 provinces were continuously monitored using Malaise trip during the field season.The results showed that the number of species of parasitic wasps against Hemiptera pest accounted for 20.62-27.37% of total species and 29.81%-57.84% of total amounts.The number of species and individuals of Mymaridae wasps were the highest among the parasitic wasps,accounting for28.57-39.39% and 62.80-87.73% of total,respectively.Meanwhile,the parasitic wasps against rice planthopper consists to the greatest part,accounting for19.72-29.41% and 57.47-85.84%,respectively.Anagrus nilaparvatae,Mymar taprobanicum,Paracentrobia andoi,Oligosita shibuyae,O.nephotetticum,G.flavifemur,H.apicalis,these 7 species could collected over all sites suggesting they are wide distributed species.4.Dynamics of two groups of important rice planthopper parasitic wasps in paddy fieldsMymarids and dryinids are two major parasitic wasps,Mymarids against eggs and dryinids parasitism /feed on the nymphs and adults.Anagrus nilaparvatae,A.optabilis,A.toyae were three major parasitic wasps in Fuyang,Zhejiang,according to the four consecutive years investigation.The combined parasitic rate of all three parasitoids was the highest at the yellow ripening stage with 12.33%;the lowest at the full heading stage with 2.16%.A.nilaparvatae was the most common species among them.The planthoppers parasitized by dryinid would be found under the light trap over all areas.Gonatopus flavifemur and Haplogonatopus apicalis were two dominant dryinid wasps.The highest parasitic rate,4.03% of WBPH was reported in Yizhou,Guangxi,and the highest parasitic rate,2.23% of BPH was reported in Qionghai,Hainan.There were Gonatopus flavifemur,Haplogonatopus apicalis,Echthrodelphax fairchildii and Gonatopus nigricans collected from rice fields in Fuyang,Zhejiang over 4 years investigation.The highest parasitic rate of rice planthopper was 10.1% in yellow ripening stage and the lowest was 1.07% in tillering stage.In addition,the parasitic rate of Haplogonatopus apicalis was the highest at tillering stage and jointing stage,and the parasitic rate of Gonatopus flavifemur was the highest at breaking stage to yellow ripe stage.5.Biocontrol capacity of Gonatopus flavifemur associated with different stages of brown planthopperG.flavifemur could parasitize and feed on BPH.The parasitic rate was highest on4 th instar nymphs(58.52±5.69%),and the feeding rate was highest on 1st instar nymphs(38.52±3.19%)according to our laboratory study.If parasitize on male BPHs,the cocooning rate of F1 generation was significantly lower in compared to parasitize on other stage of BPHs.There were more female offspring emerged if parasitize on the 5th instar nymphs.Both the parasitism and host-feeding functional responses of G.flavifemur to different BPH stages fit well with Holling type II model,along with the results of parasitism and feeding rates under different host stages.Meanwhile,the searching efficiency of parasitic was showed negative relation to its density,it is similar to the interference coefficience.The results indicated that there was a strong interference among dryinid wasps.6.Effects of temperature on biological traits of the Gonatopus flavifemurG.flavifemur could survive over the range of 17-36℃,the optimum suitable temperature ranged from 27℃ to 32℃.And the most suitable temperature is 27℃.The 12℃ and 38℃ were the unsuitable temperature zones.The developmental threshold temperature of male and female were 11.85±0.52℃ and 11.99±0.55℃,respectively.The generation effective accumulative temperature of male and female were 337.62±29.38d·℃ and 343.82±32.34d·℃,respectively.In addition,cocoons stored at low temperature 10℃ and 8℃ for 7-15 days had little effect on them.This results provided a necessary information for its commercial application.7.Artifcial rearing Gonatopus flavifemurThe life table was constructed based on the growth and development of G.flavifemur under the optimum temperature and host stages.The life table parameters such as population survival rate,fecundity,female parasitism and predation rate were obtained,and the population growth trend under unrestricted conditions was predicted.These resluts provided the important evidences for the breeding G.flavifemur artifically and continously.Additionally,by comparing the adult longevity,parasitic rate,feeding rate and offspring development of different generations of G.flavifemur,these parameters were all decreased along with generation reared.We concluded that there was obvious population degradation of G.flavifemur reared.Population rejuvenation couls be achieved by introducing wild populations and interbreeding with populations from different hosts.These measures would be useful to rear G.flavifemur successively. |
PDF Full Text Request