| Rice leaf roller, Cnaphalocris medinalis Guenee, is an important migratory pest that infested rice production in China, which has characteristics of large outbreak areas, high occurrence frequencies and heavy damages. The main influential factors on its immigration and endangering are geographical conditions, rice cropping systems, agricultural ecological environment, atmospheric backgrounds and so on, and especially the long-distance migration and re-migration of rice leaf roller are inseparable from the favorable weather conditions. The analysis of atmospheric background during the rice leaf roller’s immigrations and the occurrence states monitoring after its immigrations play an important role in the effective prevention of its endanger and the accurate evaluation of rice production losses from its damage. At present, the monitoring methods of C. medinalis is based on artificial investigation, which has the advantages of objective truth and high reliability, while there is a time-consuming drawback, and it can’t monitor a wide range of rice damage. In the last more than ten years, with the rapid development of information technology, remote sensing has a wide range of applied researches on the monitoring of crop growing process. There are many applied technology researches of remote sensing on the monitoring of pests, estimation of crop yield and other aspects. Based on the understanding on the researches of atmospheric backgrounds of pest migration and the remote sensing researches of pests at home and abroad, the investigation data of C. medinalis and the leaf roller rate of rice were analyzed and the disaster characteristics of rice after C. medinalis’s immigration was discussed. The spectral characteristic parameters which inversed C. medinalis’s damage degree reasonably was screened based on the remote sensing images of rice growth at Gaoyou and the analysis of C. medinalis’s endangering characteristics on rice and the relationship between the change of these parameters and the leaf roller rate of rice was discussed. Consequently, the relationship between the succession of C. medinalis’s occurrence (included its immigrating heads and the leaf roller rate of rice) and the changes of these parameters was ascertained. According to the obvious changes of the leaf roller rate of rice and the spectral characteristics parameters, a great immigration event of C. medinalis occurred in the rice-growing region of Gaoyou which caused the remarkable changes of the leaf roller rate of rice and the spectral characteristics parameters was selected as a typical case and Hysplit model, a online trajectory computing platform on NOAA (National Ocean and Atmosphere Administration in USA), was used to analyze the immigration trajectories and the pest sources of C. medinalis into Gaoyou. Combined WRF model (Weather Research and Forecast model) with the reanalyzed meteorological data from NCEP (National Center of Environmental Prediction in USA), the numerical simulation of the atmospheric backgrounds in C. medinalis’s immigration process was conducted and the atmospheric circulation backgrounds, atmospheric dynamical conditions, atmospheric thermal conditions and atmospheric moisture condition influenced on the immigration were diagnosed and analyzed. The main results are as follows:1. In this paper, Gaoyou City in the rice-growing region of the central part of Jiangsu Province was selected as the study area and HJ-1A/IB satellite images as the data sources was used to analyze the spectral characteristic parameters of the experiment field and the contrast field, and a correlation between the extracted spectral characteristics parameters and the damage degree of rice caused by C. medinalis was analyzed, the results showed that (1)The rice leaf roller occurred severely, the peak period is more, duration is longer, most of the rice leaf roller were moved from outside. (2)The occurrence of rice leaf roller had a significant impact on spectral characteristic parameters. We found that the increasing of the moths amount (or the occurrence grade) made the spectral parameters. decreased (3) Spectral parameters have a very significant impact on the pest monitoring of rice. Correlation analysis of the present study show that, the inversion effect of EVI and NIR are significantly better than NDVI. DNIR showed a significant positive correlation (p <0.01, R=0.718) with rates of rolled leaf, DEVI showed a significant positive correlation (p<0.05, R=0.564) with rates of rolled leaf, while the correlation between DNDVI and rates of rolled leaf was not significant. (4) Combined the investigation and analysis of insects in the field with the spectral parameters, the results of this study proved that it is feasible to using HJ satellite images to monitor and warn the outbreak and the development of rice leaf roller. The monitoring results played a proper role in the early warning of rice leaf roller and provided a possible approach for subsequent monitoring of pest study.2. In order to illustrate the influence of atmospheric backgrounds on the great immigration process of C. medinalis at Gaoyou in 2013, a great immigration event of C. medinalis occurred during the period from 28th to 29th, August in 2013 was selected as a typical case. Hysplit model was used to analyze the immigration trajectories and the pest sources of C. medinalis at Gaoyou. Combined with the reanalyzed data from NCEP, WRF model (Weather Research and Forecasting model) was used to the numerical simulation of the atmospheric backgrounds in this immigration process of C. medinalis. After the diagnosis and analysis, the influence of the atmospheric circulation backgrounds, atmospheric dynamical conditions, atmospheric thermal conditions and atmospheric moisture condition on the process were revealed. The results showed as follows:(1) In this immigration process, the typhoon weather system situated the northeast part of the East China Sea had an obvious influence on the immigration of C. medinalis into Gaoyou. (2) The south wind and southwest wind on 925 hPa isobaric surface was advantageous to the immigration of C. medinalis into the rice-growing regions in Gaoyou toward the north and northeast directions. (3) The rainfall in this process played a main role on C. medinalis’s immigrations and landing while the effect of the sinking airflow was weak. (4) As a hygrophilous pest, the excellent moisture conditions satisfied with the need of C. medinalis for the moisture environment where the relative humidity of all migratory levels were more than 80% in Gaoyou. (5) The migration temperature condition was suitable. The temperature of adequate migratory layer (from 500 to 600) was more than 18℃ at all. Therefore, the temperature conditions had no restrictive influence to the immigration of C. medinalis. In conclusion, the meteorological conditions were favorable to the mass immigration of C. medinalis into in the rice-growing region of the central part of Jiangsu Province. (6) The remote sensing images before and after the immigration peak of C. medinalis can verified timely and effectively the atmospheric backgrounds on the impact of C. medinalis’ immigration and bursting endangering on the rice growth. |
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