| Spodoptera frugiperda(J.E.Smith),also known as Fall armyworm.It is an important pest on corn crops.In order to control S.frugiperda more scientifically,the occurrence dynamics of adults and larvae of S.frugiperda in Haikou,Danzhou and Sanya of Hainan Province were monitored by manual investigation and high-altitude lamp trapping,and its harm degree,main harm period and migration route were evaluated and analyzed;The economic threshold of S.frugiperda harming corn field was discussed through the method of artificial catching and covering in the field;Five commonly used insecticides were selected for comparative analysis of control efficacy,so as to put forward reasonable drug suggestions for the safe control of S.frugiperda.The results are as follows:1.In 2020 and 2021,the total amount of Spodoptera Rapa collected by a single high-altitude lamp in the whole year is: 478 and 124 in Haikou City,respectively,and the male female ratio is 3.02:1 and 3.27:1;In Danzhou City,there are 52 and 32 heads respectively(the monitoring time is short in 2020),and the male female ratio is 0.85:1and 0.95:1;There are 145 and 109 heads in Sanya,respectively,and the male female ratio is 0.86:1 and 0.73:1;The total number of single sex attractants in Danzhou City in the whole year was 41 and 12 respectively.The overall insect population in 2021 is significantly lower than that in 2020,and the ratio of light induced male to female in Haikou and Danzhou has an upward trend.Comparing the number of larvae in the control area and non control area,it is speculated that artificial control is the main reason for the decline of S.frugiperda in 2021.There is a certain correlation between the change of insect population and the change of local temperature in the three places.2.Using the hybrid single particle Lagrangian integrated trajectory model(hysplit),the migration trajectories of S.frugiperda in the peak period of high-altitude lamp monitoring in Haikou and Sanya of Hainan Province were pushed forward.The results show that Hainan Province is located in the east of northward migration.Spring(January March)began to migrate northward.S.frugiperda in Haikou City is mainly relocated to Guangdong and Guangxi provinces,and the landing probability is46.50 % and 38.42 %.Sanya’s settlement area is basically the same as that of Haikou,mainly in Guangdong and Guangxi,with the settlement probability of 16.82 % and21.45 %.There is also a certain probability of landing in Yunnan Province,with a landing probability of 10.21 %.3.The third instar larvae of S.frugiperda with different densities were inoculated in the field to simulate the natural harm and study its economic threshold.The results showed that the economic thresholds of three stages of maize growth(v4-v6,v8-v10 and v12-v14)were 6 ～ 8 individuals /20 plants,12 ～ 20 individuals/20 plants and 19 ～24 individuals/20 plants,respectively.At this threshold,the maximum economic benefit can be obtained.4.The comparison results of field control effects of five insecticides on S.frugiperda are as follows: 200 g/L chloramphetamine benzamide suspension and5 % methylabamectin Benzoate Microemulsion had the best control effect and quick effect.150 g/m L ninchongwei EC had the worst control effect.Bacillus thuringiensis G033 A wettable powder has the longest effective period.200 g/L chloramphetamine benzamide suspension and 5 % methamphetamine Benzoate Microemulsion are recommended as the preferred pesticides in the areas with serious occurrence of S.frugiperda,and Bacillus thuringiensis G033 A wettable powder is recommended in the areas with mild harm. |
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