| Bradysia odoriphaga Yang et Zhang, a kind of the most important vegetable pests, could impact the quality and production of host plants seriously due to its extensive incidence and severe harm. Biological characteristics at different temperatures were analysed using the age-stage, two-sex life table to provide the theoretical basis for prediction and integrated control. Through mensuring the toxicity of7pesticides and the enzymatic activity of7enzymes of the poisoning test insects, as well as the protein content, this paper had a preliminary investigation into the action mechanism of insecticides, which could possess reference in development and application of new pesticides to control B. odoriphaga.The intrinsic biological characteristics of B. odoriphaga were studied at15℃,18℃,21℃,24℃,27℃and30℃at a constant temperature in laboratory using the age-stage, two-sex life table. In the range of temperatures from15℃to30℃, the intrinsic rates of increase (r) were0.07363d-1,0.09243d-1,0.1224d-1,0.1546d-1,0.1832d-1and0.1779d-1, respectively. The finite rates of increase (λ) were1.0764d-1,1.0968d-1,1.1302d-1,1.1671d-1,1.2011d-1and1.1947d-1, respectively. The net reproduction rates (Ro) were43.7offspring,46.7offspring,52.7offspring,53.6offspring,62.0offspring and50.6offspring, respectively. The mean generation times (T) were51.3d,41.6d,32.4d,25.8d,22.5d and22.1d, respectively. Starting with an average pair of young adults representing the population, the dynamic trends of population growth of B. odoriphaga at these temperatures for60days were simulated based on the population parameters.Developmental times of the whole generation of B. odoriphaga at15℃,18℃,21℃,24℃,27℃and30℃were50.53d,39.94d,31.97d,24.75d,21.86d and21.22d separately. The results showed that as the temperatures rose gradually, developmental durations of different stages of shortened and the developmental rates accelerated. Developmental time of the female larvae was always longer than that of the male larvae. Developmental threshold temperatures and effective accumulated temperatures were calculated by liner regression method and direct optimization method. The coefficients of variation indicated that the liner regression method was superior to direct optimization slightly for male larvae and whole generation while the direct optimization was more suitable to other stages. Developmental threshold temperatures calculated by direct optimization for egg, larva, pupa and the whole generation were3.77℃,5.44℃,4.49℃and5.49℃respectively, and the effective accumulated temperatures for egg, larva, pupa and the whole generation were86.03℃,312.19℃,71.53℃and487.28℃respectively. According to the meteorological data of Tai’an in2006～2012, B. odoriphaga was forecasted that it would occur about8～9generations every year in Tai’an.Stomach-contact combination toxicity method was used indoor to compare the toxicity of osthol, azadirachtin, matrine, celangulins, sabadilla, pyriproxyfen and phoxim to the3rd instar larvae. The result showed that the effects of phoxim and pyriproxyfen were best and their LC50were1.81mg/L and3.84mg/L separately. The toxicity of osthol was the highest among these5botanical insecticides and its LC50was41.68mg/L, followed by matrine (LC50=95.75mg/L). However, lethal effects of celangulins and sabadilla to the3rd instar larvae were minor.The3rd instar larvae were treated with25mg/L and100mg/L osthol, while using the test insects without osthol as the control, and the enzyme liquids at6h,12h,24h,48h and72h after treatment were extracted. The dynamics of enzymatic activity of7enzymes, including AChE, GSTs, ACP, AKP, MFO, amylase and protease, and the protein content of the insects were tested. The results indicated that the change of activity of these emzymes of the larvae treated by osthol reparesented obvious timed-dosage effect. Enzymatic activity of AChE, AKP, amylase and protease reduced as the treating time prolonged, and showed the inhibition effect. However, the enzymatic activity of GSTs elevated with the prolonging of treating time and presented the inducing effect. Enzymatic activity of ACP of the treatment group was raised first and then decreased, while the enzymatic activity of MFO was activated first, then repressed and then activated again. Protein contents of the treatment group and the control group both rose as treatment time prolonged and peaked at48h, then decreased. Compared with25mg/L osthol,100mg/L osthol excerted more significant effect on the enzymatic activity and the protein content of the treated larvae. |
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