Studies On Insecticide Resistance And Its Mechanisms In Bemisia Tabaci (Gennadius)

Bemisia tabaci (Gennadius), an important pest caused serious damage to agricultural crops in many countries throughout the world, has developed resistance to many conventional insecticides such as organophosphates, pyrethroids and carbamates, and in some regions, resistance to insect growth regulators and neonicotinoids is quite common and widespread. In this paper, insecticide resistance and its mechanisms in field populations of adult B. tabaci in Fujian province of China were studied, in order to provide theoretical basis of IPM and IRM program of B. tabaci. The main results obtained were as follows:The biotype status of B. tabaci collected from 8 representative geographical locations and host plants in Fujian province 2003-2004 was determined by both using Mitochondria cytochrome oxidase I (mt COI) as markers and using squash silverleaf assay. Of 720 characters examined for COI, all 8 populations yielded the most same sequence, which showed little diversity and shared 99.6-100% identity with the 11 biotype B reference sequences. Three distinct clades were revealed in mt COI tree, clade one included all of B. tabaci collections and reference biotype B populations, clade two and three consisted only of biotype Q and biotype A populations. According to squash silverleaf assay, all populations of B. tabaci can induce typical squash silverleaf. The results indicated that all 8 populations were of the biotype B.Resistance ratio of the B.tabaci adults to imidacloprid , acetamiprid and thiamethoxam was detected as 1.22, 3.28 and 2.49 fold by using adult leaf-dip bioassay and 1.37, 4.27 and 3.26 fold by using systemic bioassay respectively, which showed the same resistant level detected by two bioassay methods. The toxicity of imidacloprid to different age adults (1, 3, 7, 15, 20 days after emergence) and naturally mixed ages in B. tabaci was detected by using adult leaf-dip bioassay. The values of LC50 were 0.6795-0.8577mg·L^-1 for different age adults without significant difference, averaged 0.7759mg·L^-1. The values of LC50 by four tests were 0.7118-0.8549mg·L^-1 for naturally mixed ages without significant difference, averaged 0.7839mg·L^-1. There was no significant difference of LC₅₀ between naturally mixed ages and different ages. In addition, the results showed the same resistant level detected by using cotton leaf and...