The insect-resistant effect of transgenic hybrid poplar 741 with two insect-resistant genes was tested in laboratory. The indexes of general mortality, each instar mortality, development period and speed of each instar, weight increasing rate etc, were used for evaluations. Results showed that different clone of transgenic hybrid poplars had significant different insect resistances, and hereby four different resistant levels were divided. They were high resistant, moderate resistant, low resistant and non ...