Occurrence Regularity And Forecasting Research Of Brown Planthopper Nilaparvata Lugens (St(?)l) And Whitebacked Planthopper Sogatella Furcifera (Horváth) After Immigration

Brown planthopper, Nilaparvata lugens (Stal) and whitebacked planthopper, Sogatella furcifera (Horvath) are two important long-distance migration insect pests that cause great losses to rice yield in China. Their occurrence area and the frequency increased in late 30 years. There are many researches about the two pests in China and it is prolific about Middle and East of China but deficient about the southwest of China. The occurrence regularity and forecasting study of brown planthopper and whitebacked planthopper after their immigration are revealed in this paper by using the two years field investigation, indoor trial from 2008 to 2009 in Xiushan county and historic data of Xiushan and Jiangkou county which locate in the southwest of China. Based on the knowledge of biology ecology, taxonomy, statistics, systematic and the mastery of software of EXCEL,SPSS,SURFER,ArcGIS, the study goes well and the main results are summarized as follows:1. The occurrence regularity of brown planthopper and whitebacked planthopper in rice field and light-trapped was analyzed by using 20 years historic data collected in naturally-occurred rice plots and trapped by ordinary incandescent light since 1990 in Xiushan, Chongqing. The results showed that the first appearance date of brown planthopper had the tendency of postponing, while whitebacked planthopper had the tendency of advancing. The first appearance date of whitebacked planthopper was 16.68±17.58 days earlier than brown planthopper's. There were two occurrence peak of rice planthopper in naturally-occurred rice plots. The first one was mainly caused by whitebacked planthopper and the second one was by brown planthopper. The damages caused by the two insects during occurrence peaks were all great and the area was large. The occurrence peak of brown planthopper in rice field was mainly in early or middle August in 1990's but in late August from 2000 to 2009 and the occurrence peak of its macropterous was mainly in middle August in 1990s but in late August in late 10 years. So the occurrence peak of brown planthopper and its macropterous in the field had tendency of postponing.The occurrence peak of whitebacked planthopper in rice field was mainly in middle July in 1990s but in early July in late 10 years and the occurrence peak of its macropterous was in middle July or early August in 1990s but in middle or late July in late 10 years. So the occurrence peak of whitebacked planthopper and its macropterous in the field had tendency of advancing. The peak of light-trap catches of brown planthopper was mainly in late August and whitebacked planthopper was in early or late July. The quantity of whitebacked planthopper trapped by the light was larger than brown planthopper during rice growing stages mainly but smaller than brown planthopper after the rice harvestry in all years. The back immigration peak of brown planthopper was earlier than whitebacked planthopper because the former is in middle Sept. and the later was in late Sept. or Oct..2. To provide a theoretical basis for its integrated control, dynamic process and spatial pattern of the whitebacked planthopper after their immigration were studied. Models of space variation were constructed at the directions of east-west and south-north based on the geostatistical method by using survey data from the transplanting to ripening of the rice in the scale of 900 m2 in Xiushan, Chongqing in 2008. The variograms showed the higher population density was the greater space variation became for both nymphs and macropterous. Average space variation of nymphs was 38.7% caused by the random factor and 61.3%caused by the autocorrelation, and the random degree of space variation became greater as the rice grew up. Space-related distance of nymphs was 18.99 m in the direction of east-west and 25.09 m in south-north averagely. Average space variation of macropterous was 37.6%caused by the random factor and 62.4%caused by the autocorrelation and space-related distance was 12.86 m in the direction of east-west and 28.85 m in south-north averagely. The application of isoline map based on Surfer8.0 to these data provided more detailed information to the spatial dependence and structure. The result showed the aggregated scope in the south to north was larger than in the east to west for both nymphs and macropterous. That is to say south to north is the main direction for the whitebacked planthopper nymphs and macropterous to aggregate and diffuse.3. According to the comparatively complete investigation field data in Xiushan, Chongqing from 2003 to 2009, the spatial distribution and dynamics of brown planthopper and whitebacked planthopper were analyzed in this county. The result showed that the spatial distribution patterns of whitebacked planthopper were mainly aggregated in all years and the centers of aggregation and distribution patterns changed with time. In general, the density grades were higher in the middle area of the county including Guanqiao, Guanzhuang, Pingkai and 4 years aggregation center was in these areas. Its grades were lower in mountain area such as east, west, south and north of the county. The aggregation center in 2007 was in Aikou and Lanqiao, which is the south of the county, and it appeared in Pingma in 2008, which is the east of the county and in the north Haiyang and west Tangao in 2009. The spatial distribution of brown planthopper is different from whitebacked planthopper based the late 3 years'investigation data. The density grades were higher in middle and west, whereas its grades were lower in southeast of the county. The higher density grade appeared in Rongxi, Tangao, Guanzhuang, Zhonghe. The reasons of spatial distribution difference between brown planthopper and whitebacked planthopper need more investigation.4. Community structure and temporal niches of brown planthopper and whitebacked planthopper and their natural enemies including spider, staphylinid, Cyrtorhinus lividipennis, Micraspis discolor, Dryinidae in hybrid and conventional rice field were researched. The quantitative characters of the occurrence of each group and the condition of resource utilization were analyzed. The following and control function of the natural enemies to rice planthopper was inquired. The result showed that the quantity of brown planthopper is very small and whitebacked planthopper and natural enemies increased gradually before the rice heading stages. Then whitebacked planthopper decreased and brown planthopper increased and natural enemies kept in stable state which means the insect and the enemies keeps in balance state. The temporal niches breadth of every group was different in 2 paddy fields and the spiders'was greatest in both kinds field, but it was very small for Cyrtorhinus lividipennis, Micraspis discolor and Dryinidae. The niche overlap of rice planthopper and natural enemies means the time possibility of predation or parasitism. In hybrid rice field, the greatest niche overlap was rice planthopper and spider and then was rice planthopper and staphylinid. The greatest niche overlap index was rice planthopper and spider and then was rice planthopper and Cyrtorhinus lividipennis in conventional rice field.5. By using the transition probability method of Markov chain theory, the transition probability matrix of 1 to 5 steps was constructed based on the time series data of brown planthopper and whitebacked planthopper surveyed in rice paddy from 1983 to 2007 in Xiushan county, Chongqing, and trapped by the light from 1977 to 2007 in Jiangkou county, Guizhou province, China. The weight of every step by the rewarding accuracy of each step in transition probability matrix was calculated and the occurrence degree of the sixth years was predicted based on the occurrence status of the previous 5 consecutive years. Reexamining the 20 years actual occurrence of field in Xiushan and 26 years of light trap catches in Jinagkou.The result showed that the Markov chain theory has great simulation effect and nonparametric Wilcoxon paired sample test showed there were no significant difference between the actual and predicted occurrence in the 0.05 level for both brown planthopper and whitebacked planthopper. And the models accurately predicted the light occurrence in 2008 for both pests. The transition probability matrix and the weights constructed in this study have great guiding significance to forecast the occurrence grade of the two planthoppers for Xiushan, Jiangkou and its neighboring areas. It offers a rapid and effective method for the long-term predictability of the pests.6. The data of weather and rice planthopper investigated in the field and light-trapped was collected in Xiushan, Chongqing from 1990 to 2006. Taking the data of occurrence peak in the field as independent variable and the data of light-trapped and weather as dependent variable, the forecasting model of occurrence peak of brown planthopper and whitebacked planthopper in the field was constructed based on stepwise regression analysis. And then we investigated the disaster forming reason of brown planthopper and whitebacked planthopper after their immigration. The result showed that the occurrence peak was not only correlated with the weather condition but with the immigration quantity for the both insects. The occurrence peak of brown planthopper in field was positively correlated with the immigration of the month or the recent month but there was no significant relationship with the immigrated female adult which has the ability of reproduction. The occurrence peak of whitebacked planthopper in the field is positively correlated with the immigration of the previous months but has little relationship with the immigration of recent month. So the conclusion is that the brown planthopper formatted disaster soon after their immigration and whitebacked planthopper formatted disaster with their reproductive generations.7. Standard seedling stage test was used to identify the biotype of brown planthopper of Xiushan county in 2008. Five rice varieties with different resistance gene such as TN1, Mudgo, ASD7,Rathu Heerati, Babawee were used to study the biotypes of brown planthopper collected from countryside of Qingxi and Pingkai. The result showed that Mudgo and ASD7 which contradict biotype of 3 and 2 were all dead besides the sensitive TN1. It suggested there were biotype 2 and 3 of brown planthopper in Xiushan county.