| Sogatella furcifera(Horváth),Nilaparvata lugens(St?l),Cnaphalocrocis medinalis(Guenée)and Mythimna separata(Walker)are the main migratory pests in rice production in Sichuan Province.In recent years,the occurrence area and outbreak frequency have increased,causing serious harm to rice production.Based on the principles of insect population ecology,this study systematically studied the population dynamics and monitoring results of four migratory pests after landing in Sichuan rice area between 2013 and 2018,by using the techniques of light trapping,system investigation,ovary anatomy,physiological characteristics analysis,linear discriminant function,trajectory back analysis,etc.The main results are as follows:1.The key factors influencing the population dynamics and the degree of occurrence of rice planthopper in Sichuan rice region were identified From 2013 to 2018,combined with the light trapping and field systematic investigation of white backed Planthopper and brown planthopper,the occurrence regularity of rice planthopper in Sichuan rice area was as follows: there were sporadic adults migrating to Xuyong County in the middle and late May,and a large number of adults were continuously migrating from the end of may to the middle of June and from the end of July to the beginning of August.In late July,with the propagation of local rice planthoppers and the continuous migration of foreign sources,there was a peak period of damage mainly caused by white backed planthoppers.The amount of insects in the fields of southern Sichuan rice area and Eastern Sichuan rice area would remain high,and the amount of insects in some fields of Northern Sichuan rice area would also be high.By the end of August,the rice planthopper had moved out continuously,and the damage in the field decreased.White backed planthopper was the main pest in Sichuan rice area,while brown planthopper mainly occured in Xuyong county.According to the48 hour trajectory of rice planthopper,the main migration of rice planthopper in Xuyong county and Dachuan District in South Sichuan and Mianzhu City in North Sichuan was from the migration of rice planthopper,which showed the process of rice planthopper from outside Sichuan to central Sichuan.Temperature and precipitation were important factors that affected the occurrence and growth of rice planthopper.Therefore,based on SPSS software,using the method of step-by-step discriminant analysis,from the temperature and precipitation that affected the occurrence of riceplanthopper,this study screened out the ten day average temperature and ten day accumulated precipitation that can reflect its change,and established discriminant function to judge the occurrence of rice planthopper Farewell.Through analysis and research,the key factors that can affect the occurrence degree of rice planthopper in Mianzhu City,dongdachuan district and Xuyong County in the north of Sichuan Province were the average temperature in the middle of April,the accumulated precipitation in the middle of April and the accumulated precipitation in the last ten days of April,the key factors that can affect the occurrence peak of rice planthopper in Mianzhu City,dongdachuan district and Xuyong County in the south of Sichuan Province are the accumulated precipitation in the last ten days of April Accumulated precipitation in late May.Through the classification and back analysis of the established linear discriminant function,the discriminant accuracy was 77.8% and 88.9%respectively,which was basically consistent with the actual situation,providing the feasibility for the use of linear discriminant function to determine the occurrence degree and peak of rice planthopper.2.The key factors affecting the population dynamics and the degree of occurrence of Cnaphalocrocis medinalis in Sichuan rice region were determined From 2013 to 2018,combined with the light trapping and field systematic investigation of rice leaf roller,the occurrence rule of rice leaf roller in Sichuan rice region was as follows: it can appear in Xuyong County,southern Sichuan rice region as early as the first half of June,and in Northeast Sichuan rice region at the end of June,which showed that the occurrence of rice leaf roller in southern Sichuan was earlier than that in northern Sichuan and Eastern Sichuan rice region;the field damage period was concentrated from the beginning of July to the end of August.According to the migration of rice leaf roller back tracking in 48 h,the track back tracking points of Xuyong County in southern Sichuan rice district were mainly distributed in the surrounding provinces of Sichuan,such as Chongqing and Guizhou,etc.,while the track back tracking points of Dachuan District in eastern Sichuan rice district were mainly distributed in Hunan,Chongqing and Hubei,etc.,while the track back tracking points of Mianzhu City in northern Sichuan rice district were mainly distributed in Meishan and Bazhong of Sichuan Province,Zigong,etc.,a small part of which was located in Chongqing,a province around Sichuan.The results showed that the rice leaf rollermoved into Sichuan Basin from outside the province and gradually entered the central part of the province.The main reason for the occurrence of rice leaf roller was the large number of migration sources and the suitable climatic conditions in the later period.It had been found that the meteorological conditions such as precipitation,temperature and humidity were the important factors that affected the migration of rice leaf roller.Therefore,based on the SPSS software,the method of step-by-step discrimination analysis was adopted in this study to screen the energy from the temperature and precipitation that affected the dynamic occurrence of rice leaf roller.It was enough to provide the ten day average temperature and ten day accumulated precipitation and other factors that reflected the change,and established the discriminant function to distinguish the occurrence of rice leaf roller.Through analysis and research,the key factors that can affect the occurrence degree of rice leaf roller were the average temperature in the first ten days of April,the average temperature in the middle of April and the accumulated precipitation in the first ten days of April,the key factors that can affect the peak of rice leaf roller were the average temperature in the first ten days of May and the accumulated precipitation in the middle of May.Through the back analysis of linear discriminant function,the discriminant accuracy was 72.2% and 83.3% respectively.Selecting the key period and key factors was the key to the medium and long-term prediction,which provided a scientific basis for the control strategy of rice leaf roller.3.The source characteristics of rice leaf roller in Sichuan rice region were clarified There were 6 generations of rice leaf roller in Dachuan area of East Sichuan,the 3rd generation was basically immigrated,the 4th generation was all or mostly immigrated or locally propagated,the 5th generation was locally propagated and the 6th generation were mostly immigrated,5-6 generations of rice leaf roller in Xuyong County of South Sichuan,the 3rd generation was immigrated,the 4th generation was all or mostly immigrated or locally propagated.The fifth generation was mostly emigrated or locally propagated,and the sixth generation was mostly emigrated.The results of this study were consistent with the results of Chapter 3.The occurrence of rice leaf roller in Xuyong county was earlier than that in Northeast Sichuan,which was caused by the migration of rice leaf roller from south to north.The results showed that the flight ability,dry weight of flight muscle,triglyceride content and the activity of energymetabolism related enzymes of flight muscle were significantly higher(P < 0.01)in the migration population than in the migration population.The results showed that the flight muscles of the rice leaf roller develop continuously before the migration activity,and reached the mature state(thick and large amount of myofibrils)when it moved out,which was closely related to the strong flight ability of the moving out population,after the long-distance migration,the female moth began to breed and lay eggs rapidly,so the flight muscles began to degrade,the moving out population the flying muscle trunk was more important than the immigrating population.In different years,the flight ability,dry weight of flight muscle,triglyceride content and energy metabolism related enzyme activity of flight muscle in Xuyong county were more than those in Dachuan District,which may be related to the sufficient food and suitable environment for the growth and development of rice leaf roller in Xuyong county.4.The key factors influencing the population dynamics and the degree of occurrence of Mythimna separata in Sichuan rice region were defined From 2013 to 2018,combined with the lamplight trapping and field systematic investigation of armyworm,the occurrence rule of armyworm in Sichuan rice area was :armyworm can't live through the winter,and the source of armyworm was from other places,from late May to early June,from late June to late June after breeding and then eclosion,from late July to early August.The migration peak of Mianzhu City was June10 to June 17,and the peak of the second generation adults was July 26 to August 16,the migration peak of Dachuan district was June 10 to June 17,and the peak of the second generation adults was July 19 to August 16,the migration peak of Xuyong county was June 3 to June 17,and the peak of the second generation adults was July 19 to July 26,2015 Day.The migration of armyworm in rice area of South Sichuan was earlier than that in rice area of North Sichuan and East Sichuan,and the second generation of adults had a longer duration of damage,which was consistent with the actual roundtrip of armyworm from south to north.Based on the analysis of the track push back,the 24-hour track push back points of Xuyong rice area in the south of Sichuan were mainly distributed in the surrounding provinces of Sichuan,such as Chongqing,Hunan,Guizhou,Guangxi and Yunnan,the track push back points of dadachuan rice area in the east of Sichuan were mainly distributed in Chongqing,Hunan,Guizhou and Guangxi,and a few are in Ziyang and Panzhihua of Sichuan Province,the track push back points of Mianzhu rice area in the north of Sichuan weremainly distributed.In eastern and southern Sichuan,the main source of the immigrating armyworm and the secondary immigrating and diffusing of the armyworm in the province were indicated.According to the data,the higher temperature and more rainfall in July may cause the armyworm to fall in the paddy field with lower temperature and higher humidity and lay eggs.Through SPSS software analysis,the key factors that could affect the occurrence of armyworm in Mianzhu City,Dachuan district and Xuyong County of northern Sichuan rice region,Eastern Sichuan rice region and Southern Sichuan rice region were selected as average temperature in the first ten days of July,accumulated precipitation in the last ten days of May and accumulated precipitation in the middle of July.The key factor that can affect the occurrence peak of armyworm was the accumulated precipitation in late April.Through the back generation analysis of linear discriminant function,the discriminant accuracy was 94.4%,which showed that this method can be used in production practice.In summary,this dissertation systematically studies the population dynamics and rules of rice planthopper,rice leafroller and armyworm in Sichuan rice area,and constructs a more simple and feasible prediction method of four main migratory pests in Sichuan rice area,which provided a scientific basis for the control strategy of migratory pests. |
PDF Full Text Request