Study On Monitoring And Mechanism Of Spinosad Resistance In Megalurothrips Usitatus (Bagnall)

Megalurothrips usitatus(Bagnall) is classified as the Phylum of Thysanoptera,Thripina (Stephens) Priesner,the Genus of Megalurothrips Bagnall.It is an important agroforestry pest.In Malaysia, Megalurothrips usitatus (Bagnall) are one of the most serious pests of mango, which is badly damaged and difficult to control,causing huge losses to the mango industry. It is the most important agricultural pest causing damage to Leguminous plants in Africa and India, and it has not been managed and controlled effectively so far. Megalurothrips usitatus (Bagnall) is also an important pests of cowpea in Hainan Province. Chemical control is served as the major method for the controlling of Megalurothrips usitatus (Bagnall) to ensure the development of the vegetable industry in winter in Hainan Province. Spinosad plays an important role in the effective pesticides present. With the large - scale use of spinosad, pesticide resistance of Megalurothrips usitatus (Bagnall) on spinosad need to be investigated urgently.There are four parts in this essay: 1. Establish the susceptible population and screen the resistant population. 2. Resistance monitoring. 3. Research on the mechanism of resistance. 4. Management of the resistance on Megalurothrips usitatus(Bagnall).The results indicate:(1) By screening indoor susceptible population and introducing Hawaii susceptible population and indoor susceptible toxicity baselines of Megalurothrips usitatus (Bagnall), the result indicates the LC50 is 0.172mg/L and the slope of the baseline is 2.134, providing a basis for the surveillance of the field resistance.(2) Investigation indicates that the population of Megalurothrips usitatus(Bagnall) has shown clear resistance on spinosad across Hainan with the resistant index being between the interval of 3 and 27 through a two-year period surveillance.Relatively high application districts including Sanya, Ledong has shown medium resistant level.(3) Research concern indicates that the resistance has nothing to do with antioxidant enzyme superoxide dismutase (SOD) nor catalase (CAT), but is connected with the activity of GST(4)The resistance is connected with the free amino acid abundance. The abundance of histidine can affect the susceptibility.(5)Research dealing with different population’s diversity of bacteria in the digestive tract indicates that the abundance, diversity and the community composition are in close relation to the resistance. The abundance of Luteimonas, Sphingomonas,in the digestive tract shows certain correlation with the Sensitivity. The abundance of Burkholderia, Tatumella, Ralstonia, Escherichia-Shigella in the digestive tract shows certain correlation with the resistance.(6) Based on the CO I gene to calculate the genetic distance and to construct the phylogenetic tree, it was found that the genetic distance of Megalurothrips usitatus(Bagnall) was similar to that of the five different geographical populations, and the genetic differentiation was not obvious, and the distance of the genetic relationship was related to the geographical position.(7) Indoor screening and the field assay indicate that ethyl polysaccharide has higher toxic level on the population of Megalurothrips usitatus (Bagnall) and the field resistant population. Four of the five small molecular compounds (Pul、Est、Ane、Lin)show relatively high toxicity on Megalurothrips usitatus (Bagnall). Due to its convenience for extraction and its high performance,it is possible that Lin can be used for a lead compound in further researches.