Study On The Occurrence Regularity Of Spodoptera Frugiperda In Hubei Province And The Control Effect Of Empedobacter Brevis

The Spodoptera frugiperda as a major agricultural pest,it has the characteristics of long moving distance,wide host range and heavy violent eating.The Spodoptera frugiperda first occurred in the Americas and has posed a serious threat to national food production security since the invasion of China in January 2019.In order to further explore the field pest characteristics and climate adaptability of Spodoptera frugiperda in China.In this study,we monitored the natural population dynamics of Spodoptera frugiperda in Hubei province,analyzed the field diffusion law,analyzed the influence of rainfall and high temperature on the field population of rain and heat,and explored the control effect of biological pesticide(Empedobacter brevis)on the Spodoptera frugiperda.In order to provide a theoretical basis for the scientific control of Spodoptera frugiperda in Hubei province.The test results of this article are as follows:1.Analysis of the occurrence of natural population of Spodoptera frugiperda:Dynamic monitoring of the natural population of Spodoptera frugiperda in Jingzhou and Xinzhou,Hubei Province.According to the monitoring results,it is found that the number of Spodoptera frugiperda in Hubei Province can reach 4 to 6 generations.Since mid-to-late June,the first generation of larvae in the field began to harm and continued until mid-to-late November.Comparing the amount of Spodoptera frugiperda larvae in different Spodoptera frugiperda in Jingzhou area,we found that the larval amount in July > September > August > October,the field peak appeared in August 14(51.08 Individuals per 100 plants),July 17(48.17 Individuals per 100 plants)and September 25(44.5 Individuals per 100 plants);The number of larvae in Xinzhou area: September >Augus > July > t October > November,with three insects peak on July 25(43.6Individuals per 100 plants),September 6(25.73 Individuals per 100 plants)and September 30(35.33 Individuals per 100 plants).At the same time,the analysis of the field pests in five different maize varieties,including Chuandan silage No.1,Wannuo2000,Jindan 485,Double honey and Jinyu,found that the occurrence of the Spodoptera frugiperda in the above six maize varieties was not significantly different.2.Analysis of field diffusion rule of Spodoptera frugiperda:Transfer and diffusion test of Spodoptera frugiperda larvae in maize field.When the initial larval incubation density was between 10 and 200 Individuals per plant,the larval transposition rate ranged from 8.00% to 31.40%.The overall transstrain rate decreased with increasing larval density.The average maximum dispersal distance was 2.29 ～ 3.53 m,showing a trend of increasing dispersal distance with increasing larval density.The analysis of the 1 ～ 5 instar larvae showed that the spread occurred in larvae 2 ～ 4 instar,or more than 85.00% of the larvae,and the transfer of larvae was 3 > 2 > 4.The transfer of 1～ 2 instar is mainly passive transfer by wind,and autonomous diffusion to surrounding plants after 3 instar.With age,the larva strengthens and its distance to transfer increases.Combining the diffusion direction and wind direction,we found that when the wind direction was dominated by east wind and southeast wind,75.00% of the larvae spread in the field from east to west,which indicates that there is some relationship between the transfer and diffusion direction and wind direction.3.Effect of environmental factors on the development and survival of Spodoptera frugiperda:1)Development and survival of Spodoptera frugiperda larvae in maize field: The developmental epoch of the Spodoptera frugiperda larvae treated with different feeding dates was July(15.8 d)< September(16.9 d)< June(18.1 d),The mean temperature during the survey period was July(31.09℃)> June(28.95℃)> August(28.83℃).The above results show that the field developmental period of larvae is mainly affected by temperature: when the temperature is high,the developmental developmental period of the moth larvae is extended accordingly.Rainfall is a key factor affecting the natural survival rate of young larvae,and old larvae have a certain ability to resist rainfall.2)Pupation and emergence test of Spodoptera frugiperda under different soil water content: There are significant differences in the penetration rate and excavation rate of different soil water content of 20.00% ～ 40.00%,the penetration rate and excavation rate can reach more than 90.00%;when the soil water content exceeds 60.00%,the larval mortality increases with the increase of soil water content,and the depth of larvae into the soil also decreases;under 100.00% humidity,the depth of mature larvae is less than 1 cm and it is difficult to survive.There was no significant difference in adult life span under different soil water content conditions.4.Research on green prevention and control technology:The bioactivity and detoxifying enzyme activity of Empedobacter brevis against Spodoptera frugiperda were measured,the corrected mortality of the first,second and third instar larvae were 96.55%,94.92% and 78.33% respectively.After 7 days of spraying the same concentration of Empedobacter brevis in the corn field,the rate of population decline and the control effect were 93.45% and 93.78%,all were higher than matrine,and no significant difference with chloroworm benzamide.After treatment with sublethal concentrations of Empedobacter brevis,GST and Car E activity was inhibited in larvae.From the above results,it is clear that Empedobacter brevis has a high biological activity against Spodoptera frugiperda in the indoor test,and has a significant control effect in the field,which can be used to prevent and control the Spodoptera frugiperda.