Study On Monitoring Methods Of Population Migration In Cnaphalocrocis Medinalis (Lepidoptera: Pyrididae)

Cnaphalocrocis medinalis（Lepidoptera:Pyralidae）is an important rice pest in Asia.Previous studies showed that it possesses the behavior of long-distance cross-regional migration.Accurate monitoring and early warning of migratory populations are the basis of guiding prevention and control,however,there is still a lack of supporting technical system at present.In this paper,on the basis of trapping adults in the air with high-altitude light and trapping adults with food attractants in the field,trajectory analysis,anatomy of internal reproductive system and carbon and hydrogen stable isotope tracer were used to establish the analytical system of cross-sea migration,land-transit migration and ground population dynamics monitoring,path simulation and traceability of C.medinalis.The main results are summarized as follows:1.High-altitude monitoring of the cross-sea migration of C.medinalis in the South China Sea.The high-altitude light monitoring in Yongxing Island,Sansha City,Hainan Province from 2017 to 2019showed that the migration of C.medinalis in the South China Sea occurred in all seasons.But the main period of migration was in September and October,which accounted for 78.65±7.58%of the total annual catch.Trajectory analysis showed that from May to August,the rice leaf roller mainly moved from Vietnam,Cambodia and other Southeast Asian countries to the rice regions of southern China.From September to October,it moved back to Vietnam,Cambodia and other countries from Hunan,Guangdong and Guangxi.2.High-altitude monitoring of land-transit migration of C.medinalis.The high-altitude light monitoring in Lingshui County of Hainan Province from 2017 to 2019 showed that the land migration of C.medinalis occurred monthly,and the main period of migration was in September and October,which accounted for 52.22±15.03%of the total annual catch.Trajectory analysis showed that from May to August,the rice leaf roller mainly migrated from western Hainan and Vietnam to northern Hainan and South China Sea.From September to October,it mainly migrated back to western Hainan and Vietnam from Leizhou Peninsula,northern Hainan and Taiwan Island.3、Food attractant monitoring of C.medinalis in the field.The surveillance of food attractants in Guangxi,Hunan,Jiangsu and Zhejiang from June to August 2020 showed that C.medinalis migrated rapidly in the same period in eastern China from south to north.The proportion of sexual maturity of female and male moths were 81.02±24.15%and 85.94±1.46%,respectively.Trajectory analysis showed that from June to August,C.medinalis mainly from Vietnam,Laos and other places passed through Guangxi,Hunan,Jiangxi and Jiangsu,and finally moved to Zhejiang and the Yellow Sea of China.4、Isotope traceability analysis of migratory adults of C.medinalis.The carbon and hydrogen stability isotope analysis of migratory adults in the South China Sea and land from 2017 to 2019 showed that the migratory adults in the South China Sea fed on different host plants in different months,C₄ plants in January-July and October-December and C₃ plants in August-September.Hydrogen isotope values are highly positively correlated with carbon isotope values,indicating that C.medinalis,which mainly fed on C₄ plants such as corn and sugarcane,came from low latitudes.Populations that migrated to South China through the South China Sea may mainly fed on crops such as corn and sugar cane in countries such as Vietnam,while populations that migrated across the South China Sea to countries such as Vietnam may mainly came from rice growing areas in South China.The migratory adults in southern Hainan mainly fed on C₃ plants,with more than 80%monthly and yearly on average.There was no significant difference in feeding host plants in different periods.the hydrogen isotope value of northward migrating populations of C.medinalis was higher than that of southward populations.It showed that the northward migrating populations in southern Hainan may mainly come from rice and other crops in western Hainan and Vietnam.The southward migration populations may mainly come from rice and other crops in Leizhou Peninsula,northern Hainan and Taiwan Island.In this study,a monitoring and early warning system for air migration and ground population of C.medinalis was established,which can be used to monitor migration dynamics,simulate migration process and predict population reproduction.It provides a new means to further improve the technical level of monitoring and early warning of rice leaf roller and guide accurate prevention and control.