Abstract:During the growing season of 2011, the leaves of four Bt transgenic clones B1, B4, B17 and B21 of Populus deltoides × P. euramericana cv. ‘Nanlin895’ were exposed to the target pest larvae of Micromelalopha troglodyta to assess the insecticidal activity of Bt transgenic P. deltoides × P. euramericana cv. ‘Nanlin895’ under laboratory and field conditions. It was showed that all the clones had certain insecticidal activity against target pests. The corrected mortality of the target pest feeding on clone B21 was as high as 95.3%. The corrected mortalities in August and September were 35.0%-88.8% and 40.5%-95.3% respectively under field conditions. The pupation ratio was 83.3%-96.0% in CK, while in transgenic poplar that was 8.0%-76.7%, showing a significant difference between them. The development of target larvae was inhibited by Bt transgenic P. deltoides × P. euramericana cv. ‘Nanlin895’. After 8 days’ feeding, the intake and growth rate of target larvae were significantly lower than that of the CK. The effect of Bt transgenic poplars on microorganisms in rhizosphere soil was also studied and no significant difference was found in the quantities of bacteria, fungi, and actinomycete between the transgenic and non-transgenic poplars, suggesting no negative influence on the soil microorganism system.