Community Structure Of Aerial Insects And Population Dynamics Of Important Agricultural Pests In Western Yunnan

Yunnan Province is located in the southwest of China.It is the first stop for many migratory insects from Indochina Peninsula and South Asian countries to invading into China.Part of the southwest border region of Yunnan Province is located to the south of the Tropic of Cancer,where many pests can safely overwinter.In recent years,global warming has intensified,further expanding the northern boundary of pest overwintering.From 2018 to 2020,the world's major migratory pests such as fall armyworm(FAW)Spodoptera frugiperda and desert locusta Schistocerca gregaria broke out in many countries.In particular,FAW has invaded China at the end of 2018,forming a colonized population,which will be migrating from north to south for many years.Chinese scholars have also found sign of desert locust activities in Yunnan,fortunately they have not caused substantial harm.In order to cope with the aggravation of the globalization hazard situation in migratory insects,we should strengthen the monitoring and early warning system of migratory insects in the border areas of our country.In this paper,the long-term monitoring and early warning system for the cross-border migratory insects in southwest China is carried out by means of the searchlight trapping,ovarian dissection,field investigation,stable isotopes,trajectory simulation,etc.The main research results in the previous two years are as follows:1.From 2018 to 2019,Species composition and community structure of insects migration across border was clarified preliminarily,and a total of 199 insects belong to 14 orders and 60families were trapped at Lancang Station,of which Hemiptera was the dominant group,accounting for more than 50%of the annual biomass.According to the index of occurrence,in 2018,there were 14 species of constant species,including white-backed planthopper(WHBP)and Spodoptera litura,and 32 species of accessory species.In 2019,there are 9 species of constant species including FAW and S.litura,23 species of accessory species,and the rest are accidental species.2.In Lancang station,FAW moths was first captured in China on December 11,2018.It was confirmed that the early arrival of FAW in China was mainly of“corn strain”.It was monitored two peaks in 2019 occurred in May and September respectively.The origin and migration routes which immigrated to China from 2018 to 2019 are estimated,mainly concentrated in the central and northern region of Myanmar.It is estimated that migrating northward from Lancang region mainly flew to the central and northern parts of Yunnan in China and parts of Guangxi and Guizhou near Yunnan province,and the southward migrating population mainly landed in the northern part of Myanmar.The average grade of ovarian development of females in searchlight is over 3,and the mating rate is over 75%.The wingbeat frequency of moths have no significant changes during June and September 2019.From December 2018 to March 2019,the latitude of the origin of FAW immigrated to China showed a downward trend,i.e.the range of the origin of FAW continued to expand.3.White-backed planthopper is the main dominant species in the airborne insect community at Lancang Station.Its biomass accounts for more than 50%of the total trapped insect population.The peak of the annual migratory insect population presents a bimodal pattern.In 2018,the main migration peak occurred in late April,with the highest single-day trapping peak exceeding 100,000and the second peak occurring in September.The total monthly trapping amount was less than 1/6of that in April.The highest number of 100 plants in a single day in the field appeared in May,exceeding 20,000.The peak of migratory insect population in 2019 almost overlaps with the previous year,with the main peak occurring in early May,with the daily maximum insect population not exceeding 20,000,and the sub-peak also occurring in September,with the monthly total amount of trapping insects less than 1/18 of that in May.In 2018,the ovarian development grade of females of BPH in searchlight,with the proportion of individuals of grade 3 and above showing a phenomenon of from high to low and then increasing,was in good agreement with the peak period of migratory insects.The number of local overwintering BPH in Lancang is almost zero,and the main harmful population comes from the outside borders insect sources concentrated in central and northern Myanmar.It is speculated that the white-backed planthopper moved northward from Lancang in 2018 mainly flew to the central and northern Yunnan,northwest Guangxi and western Guizhou.The population moving southward mainly landed in Myanmar and northern Laos.4.In Lancang station,S.litura is a constant species during 2018-2019.The peak of migratory insects in the whole year presents a bimodal pattern,mainly occurring in May and September-October,and the primary and secondary peaks are not fixed.The proportion of female insects in searchlight during the whole year showed a"concave shape"from high to low and then increased.In 2018,the average grade of female ovary development was close to 3,with an average mating rate of more than 83%?5.Biological character parameters of 8 lepidopteran pests were measured trapped by searchlight trapping at Lancang Station.The wingbeat frequency,body length,body width and body mass of the eight pests have no significant difference in biological parameters between individuals within the species,during June and September 2019.Between species,each parameter has reached significant or extremely significant level.In summary,Lancang station has a high community diversity of aerial insect,and the dominant order is Hemiptera.White-backed planthopper is the dominant species,and its migration peak in the whole year is"double peaks"with obvious"primary and secondary peaks",2018 is the major occurrence year of white-backed planthopper in Lancang region.The hosts of FAW immigrated to Yunnan mainly on C₄ plants,which is"corn strain".It is presumed that the outside borders insect source is concentrated in the central and northern parts of Myanmar.S.litura is a constant species,and its annual migration peak is also"bimodal".The mating rate of female moths and the proportion of sexual mature individuals under light show a downward trend from March to November.This study provides practical and theoretical basis for monitoring and early warning of cross-border migration of airborne insects in the southwest border of China.