Abstract: By simulated experiments, the Fermital leaf-lost level of 25 % has been determined for 15-20 year-old plantations of Pinus densiflora initially attacked by D. spectabilis under the medium site conditions in central-south mountain areas in Shandong Province, and the amount of leaves eaten by caterpillars has been measured to be 40g/head. The regression equation, y=1275.47x-5861.72(r=0.90), has been set up between the volume of needles (y) and the diameter of breast height dbh (x). A control index of D. spectabilis in spring is set to be 11~59 head/tree for plantations with an average dbh of 6~12 cm.