| The western flower thrips (WFT), Frankliniella occidentalis (Pergande), is an important invasive insect pest. At present, it has caused serious damage to vegetable and flower crops on China’s Beijing, Yunnan, Shandong, Guizhou, Xinjiang. WFT can not only cause direct harm on vegetables and flowers by feeding, it is the most effective media of tomato spotted wilt virus (tomato spotted wilt virus, TSWV). The harm caused by spreading TSWV is much larger than direct harm caused by feeding. Spinosad is till now one of the most effective insecticide to control F. occidentalis. However, it has been reported that F. occidentalis has developed resistance to spinosad in the field. Age-stage and two-sex life tables were used to study the biological characteristics of spinosad susceptible and resistant strains of F. occidentalis, such as developmental duration, each age survival rate, population growth, body length and body width. We also studied the biological characteristics of F. occidentalis treated with or without TSWV. The sensitivities of different treatment F. occidentalis to three insecticides were determined by using leaf-tube residue method. It will provide important inforation for F. occidentalis and TSWV control through this study.(1) The results suggested that every developmental period of spinosad resistant WFT larvae was longer than that of susceptible population and the developmental time from egg to adult of susceptible strain was significantly different from that of resistant population (P<0.001). And the adult longevity of susceptible strain was significantly longer than that of resistant population. The susceptible females were significantly more fecund than resistant ones. There was significantly difference between the demographic parameters (r and Ro) of susceptible strains which were0.19and34.39d-1and those of resistant strains which were0.15,16.18d-1. The fitness of resistant strains decreased dramatically, to only0.47that of the susceptible strain. The lengths and widths of instars and adult of the resistant strains were smaller than those of the susceptible strains. And the length and width of the female adult in the resistant strains were significantly smaller than those of the susceptible strains. Spinosad resistance made adversely effect to western flower thrips growth and development, body length and width, even if western flower thrips produced more large fitness cost.(2) For the resistant strain non-treated and treated by TSWV, the developmental period of preadult were14.38and14.31d (P=0.693), respectively. The developmental period of preadult of resistant strain treated by TSWV was shorterned, which was not significant different from the non-treated thrips. The female longevity and fecundity increased of TSWV-treated thrips, which were not significant different from the non-treated thrips. The survival rates of two treatments were all higher. The intrinsic rate of increase (r) of WFT treated without and with TSWV were0.0356and0.0433d-1(P≤0.001). And the net reproduction rates (R0) of two treatments were1.972and2.210d-1(P5≤0.001), which were significant different between the two treaments. As for the susceptible strain treated by TSWV, the development period shorted (12.36d), the adult longevity increased significantly (P≤0.001), the fecundity increased as well. The R0was4.125offspring per individual which was significant higher than the counterpart susceptible control (P<0.001). The r of two treatments was not significant. On the whole, the population treated TSWV was growing faster.(3) The sensitivities of the resistant and susceptible F. occidentalis treated by TSWV to spinosad did not change much. However, the sensitivities to emamectin benzoate and chlorfenapyr decreased significantly. The results showed that the sensitivities of the resistant and susceptible F. occidentalis treated by TSWV to some pesticides reduced. It is proposed to strictly selected pesticides when the users praying. |
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