Influences of Ginkgo biloba Leaves on the Survival and Fecundity of Tetranychus urticae and Tetranychus viennensis

The influences of Ginkgo biloba leaves on survival and fecundity of Tetranychus urticae and Tetranychus viennensis were elucidated by the bioassay on resistance of G.biloba to spider mites.The mortality curve and oviposition curve of spider mites confined in Ginkgo biloba leaf with the method of petri dish were visually analysed,and then the probit analysis simulated the regression relationship between mortality and survival time.Results demonstrated that T.urticae and T.viennensis inoculated on a G.biloba leaf all died respectively in 192 h and 96 h,and there were the normal phase linear regression relations between the mortality and the survival time.The median lethal time(LT_ 50) of T.urticae and T.viennensis on a G.biloba leaf was 102.00 h and 57.32 h,respectively.There was significant difference between the median lethal time(LT_ 50) of treatment and the median mortality time(MT_ 50) of control.The fecundity of T.viennensis inoculated on G.biloba leaves was fully inhibited in four days,and T.urticae never oviposited on ginkgo leaves during the experiment.In comparing the two spider species,ginkgo leaves affected more adversely the survival of T.viennensis,while inhibited more strongly the fecundity of T.urticae.