Population Source,migration Trajectory And Light Trapping Effect Of Important Noctuid Pests During Alternation Period

Noctuidae pests such as Helicoverpa armigera and Mythimna separata are major agricultural pests in Shandong-China.Which is located geographically in the north-south regions.It can be considered as seasonal migration channel of Noctuidae pests in China.However,the dynamics of pest migrators has not been fully understood.It is of great significance to clarify their migration patterns in Shandong Province and develop trapping and control technologies for monitoring and controlling migratory pests in Shandong Province,and these patterns can be applied all over the country.For this purpose,wwe used high-altitude lights to trap and monitor major Noctuidae moths.The morphological analysis of the reproductive system was carried out to provide the basis for species identification and origin of the transitory flying insects.The process of insect migration in Shandong Province can be divided into five stages.The alternation period is the period when the north-south migration direction of insect changes.The regularity of population occurrence and its driving factors in the alternative period remain unclear.This study,combined the high-altitude air flow to simulate the migration trajectory and discussed their relationship between wind direction conversion during the replacement period and the migratory direction of these pests.We compared and studied the species on the bases of quantity and community structure of those insects,that captured by 4 high-altitude lamps with different numbers of light sources,and measured the effect of fumigation treatment on preventing the escape of collected insects,in order to provide a basic understandings by using high-altitude lamps to trap and control Noctuidae pests.The main research results are as follows:1.Analysis of development level of reproductive system of NoctuidaeAlmost 4522 species of Noctuidae were examined to compared their anatomic reproductive system.According to the development status of ovaries,the degree of development of egg particles,and the morphology of mating sacs.The development level of the reproductive system of Noctuidae was uniformly divided into 5 levels;such as,milky white transparent period,yolk deposition period,mature waiting period,oviposition peak period,and oviposition end period.The morphology of ovaries of four important noctuid pests such as Helicoverpa armigera,Mythimna separata,Spodoptera litura,and Spodoptera exigua were systematically described to provide a basis for studying the source of noctuid pest populations using ovarian anatomy grading.The morphology of mating sacs of 8 Noctuidae with large numbers and similar body shapes such as Helicoverpa armigera,Mythimna separata,Spodoptera litura,Spodoptera exigua,Agrotis ipsilon,Spaelotis valida,Athetis lepigone,Mamestra brassicae were described.The mating sacs of Helicoverpa armigera are cylindrical right-handed spirals;those of Mythimna separata are G-shaped fishhooks;Agrotis ipsilon had large coils with outer capsules;those of Spaelotis valida are band-shaped;where Spodoptera exigua are dumbbell-shaped;those near the mouth end of Spodoptera litura are red and the upper part is milky white transparent with visible inner sac cavity;those of Athetis lepigone are olive-shaped;those of Mamestra brassicae are small coils with outer capsules.This provides a basis for species identification of Noctuidae that are difficult to identify from external morphology due to loss of scales during peak collection time.2.Analysis of population structure and migration trajectory of Noctuidae during their replacement periodDuring the replacement period of insect northward and southward migration,high-altitude lamps were used to monitor and capture 9 Noctuidae(Helicoverpa armigera,Spodoptera litura,Spodoptera exigua,Plusia agnata,Agrotis ipsilon,Agrotis segetum,Mythimna separata,Athetis lepigone and Argyrogramma albostriata).The ovaries of female moths were dissected and the changes in population structure were analyzed,and the migration trajectories were analyzed in conjunction with high-altitude air flow.In July,the southwest monsoon provided air flow conditions for Noctuidae to migrate northward.In about two weeks from late July to early August,the air flow changed rapidly,and monsoon began to move southward,providing air flow conditions for southward migration.Under the influence of high-altitude air flow,9 Noctuidae such as Helicoverpa armigera,Spodoptera exigua,and Mythimna separata all had noticeable north-south migration processes.Most of the species mixed with local populations during the northward migration period and were mainly long-distance migration sources from other places,during the southward migration period.This is evidence that Shandong is not only a spring and summer breeding area for moth pests and a source of insects in Northeast China,but also a wintering place for returning insect sources from Northeast China and a passage for continuing southward migration.3.Effects of light source quantity and fumigation treatment on the trapping of Noctuidae moth pests by high-altitude lampsThree high-altitude lamps with multiple light sources,L2,L3 and L5,which were different from single light source L1,were set to induce in the replacement period.Insects were captured and recorded with L1 high altitude lamp as control.The four kinds of high-altitude lights attracted a total of 234,650 insects.It was found that the number of light source X and the number of entrapment insects Y conform to the linear equation Y=13398.91+16459.49X.The capture volume of 5 groups of the light source(high-altitude lamps)was 3.44X that of single light source.During 4 peak periods,the number of insects collected by high-altitude lamps also showed an increasing trend with the increase in the number of light sources.There was 71～95 species of insect attracted by 4 high-altitude lamps,thus Lepidoptera and Noctuaridae were the more dominant groups.The community similarity of insects captured by 4 high-altitude lamps was between moderately dissimilar and similar.During four peak periods,the community similarity of insects captured by 4 high-altitude lamps was moderately dissimilar to extremely dissimilar.The number of insects captured by fumigated high-altitude lamps increased by 22.94%compared to the control group,among which the number of insects captured during peak periods increased by 89.17%as compared to the control group,indicating that fumigation treatment can effectively reduce the escape and increase capture.