Corn rootworm (Diabrotica sp.) has becoming the most destructive and widespread insect pest in North America, causing extensive crop damage. A field experiment including a pair of conventional corn (Zea mays L.) hybrid with or without insecticide (Force 3G) and its near isoline transgenic Bt hybrid (Mon 863) was conducted for three years. Root node injury and larvae dynamics during the growing season were monitored. Stalk lodging, grain yield and harvest index were determined. Our data showed that both Force 3G insecticide and the Bt trait significantly reduced the root injury and lodging score. Compared with the conventional non-Bt hybrid, grain yield under severe infestation of corn rootworm conditions was significantly greater for the Bt hybrid and non-Bt hybrid treated with the insecticide, but the yield increase was much less in a year with low infestation of corn rootworm. Our data suggest that corn producers should be aware of the pest level and benefit-cost ratios prior to the decision on the use of Bt technology or insecticides.