| Tetrancychus vienensis Zacher is an important pest in fruit orchards worldwide. Current control of this pest mainly relies on several classes of acaricides. With the intensive use of acaricides, T. vienensis had developed resistance to different acaricides. Pyridaben and abamectin are the common acaricides used in control T. vienensis. This study built up a laboratory rearing method of T. vienensis, investigated the development of natural and laboratory populations of T. vienensis, set up the resistance strains of T. vienensis to pyridaben and abamectin, and analyzed the the biochemical mechanisms of the resistant strains to pyridaben and abamectin. Furthermore, we monitored of resistance of T. viennensis field populations to different insecticides. 1. The laboratory rearing methods and the life table of T. vienensisWe set up three methods, the detached Pyracantha fortuneana leaves, the water-cultured P. fortuneana branches, and soil-cultured P. fortuneana plants, which could be used to rear T. vienensis with P. fortuneana under condition of 25±1℃, humidity of 60%±10%, and the photoperiod of 16: 8(L: D) in the laboratory. The life-table of T. vienensis laboratory population and natural population was established using the detached leaves rearing method. The results of life table showed that net reproduction rate R0(9.113), the intrinsic rate of increase rm(0.096) and the finite rate of increase λ(1.101) of laboratory population was higher than those of the natural population.The mean generation time T(22.780) of laboratory population was lower than the natural population(24.355). 2. Monitoring of insecticide resistance of T. viennensis to different insecticidesToxicity of five insecticides to the relative susceptible strain and the resistance level of T. viennensis to five insecticides were tested by slide-dip method. Field populations were collected in apple orchards of Qianxian, Liquan, Xingping, Chengcheng, Ansai, Chunhua, Fengxiang and Fufeng of Shaanxi Province. Eight field populations showed moderate to high resistant level to pyridaben with the resistance ratio of 13.29~69.63, showed low to high resistant level to lambda-cyhalothrin with the resistance ratio of 7.99~46.74, and were susceptible or low resistant to abamectin. All the populations were susceptible to chlorpyrifos except the Fufeng population. All the populations were sensitive to thiamethoxam. 3. The resistance selection of T. vienensis to pyridaben and abamectinT. vienensis was continuously selected with pyridaben and abamectin. After 30 generations, the resistance increased to 121.57 and 21.06, respectively. The more generations selected, the higher was the resistance level. The synergistic action of PBO, DEM and TPP on the pyridaben-and abamectin-resistant population(RP and RA) were tested. The result showed that the synergism of PBO, TPP and DEM to RP and RA were all higher than the sensitive. The result also showed that the synergism ratios(SR) of RP to the three synergists(PBO, TPP and DEM) were 1.23, 5.33 and 1.99 folds respectively, and the SR of RA to PBO, TPP and DEM were 1.82, 1.76 and 1.23 folds respectively. 4. Biochemical resistant mechanism of T. vienensis to pyridaben and abamectinWe measured the activities of CarE and GSTs in RP and RA. The result showed that the activities of CarE in resistance strains were higher than in susceptible strain(SS). The activities of CarE in RP and RA were 1.36 and 1.17 folds compared with the susceptible strain. The activities of GSTs in RP and RA were 1.26 and 1.23 folds compared with the susceptible strain. Compared with the SS, the activities of GSTs in resistance strains(RS) were little higher, no significant difference between SS and RS. |
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