The Study On The Influence Of 2015-2016 Super El Ni(?)o On Occurrence Condition Of Rice Planthoppers In China

Rice planthopper is a kind of major pest in rice field who has an over 500a history in China at least.21st century,the activity of rice planthopper come to another activate period.It outbreaks in Southeast Asia and China,which is harmful to rice security significantly.The dynamics of rice planthopper is highly related to its surrounding environment.There are a lot of factors which would effect on rice planthoppers,such as the cultivation regularity,meteorology background and topography.Recent years,the frequency of extremely climate event became higher.Among them,the El Nino event which has teleconnection with weather all over the world influence ecology and biology.A super strong El Nino occurred in 2015-2016.It has obviously influence to China’s climate.Therefore,knowing how does El Nino works on rice planthopper will rise our knowledge on rice planthoppers’ occurrence mechanism and refine rice planthoppers’ occurrence pattern.For these reason,this dissertation is the analysis on rice planthopper occurrence law of east China rice planting area and Yunnan rice planting area.Besides,some studies on phototactic response rhythm of single site high light trap in Nanjing.Main research results:Rice planthopper immigration in east ChinaThe objective of this research is to determine the influence of El Nino on the occurrence of rice planthoppers in China,so as to illustrate the occurrence regularity of rice planthoppers under extreme weather.The northward migration processes of rice planthoppers in the next year(2016)after an event of El Nino were analyzed based on the data of the weather over the East Asia migration field and population sizes of rice planthoppers monitored by light traps.The light trap catches of rice planthoppers in nine provinces of southeast China in the latest decade were statistically analyzed.Grid Analysis and Display System(GrADS)was used to visualize the weather processes during the migration of rice planthoppers.HYSPLIT trajectory analysis platform was used to simulate the endpoints of an emigration event of rice planthoppers from their population source areas.The essential weather processes in the source areas of Indo-China Peninsula to the main damage regions of the Yangtze River Delta were analyzed,and their effects on the secondary environmental factors were discussed.The 2015-2016 El Nino was one of the strongest events since 1980s.This event resulted in significant influences on the weather of East and Southeast Asia.It caused the unprecedented worst drought in Indo-China peninsula,and heavy rain and floods in the south and east of China.It was found that:1)the drought of Indo-China peninsula in winter-spring brought about the decrease of the number of rice planthoppers in this area which would migrate to China;2)the heavy rainfall in the south of China led to a barrier for rice planthoppers to migrate from south to north;3)the waterlogging induced by rainfall made the number of eggs and nymphs in the fields hardly rise;and 4)high temperature in summer prevented planthopper population outbreaks.The impacts of this El Nino on rice planthoppers are not only related to the own property of this extreme meteorological event,and some certain short-term weather events during the El Nino also might be crucial for the population development of rice planthoppers.Rice planthopper immigration to Yunnan ProvinceThe occurrence scale of rice planthopper is large in Yunnan,range top 1 in this decade.Number of light trap catches in west Yunnan was much more than east Yunnan.The insect source area of Yunnan is different with the source area of Guangxi and Guangdong,only slightly overlapped.The precipitation condition in early period is the reason which lead to such a difference.Multi-points simultaneously outbreak phenomenon is very significant.Ten sites in east and middle Yunnan holding a same peak day around May 24.High light trap catches in NanjingThe immigration process in 2016 was strongly controlled by plum rain.The first peak observed under the light occurred after the plum rain stopped.The source area of rice planthoppers in Nanjing was north of Hunan,east of Hubei,north of Jiangxi and south of Anhui.The other reasons of the peaks were wind shear,rainfall and down draft.