Abstract: The effects of the Dothiorella gregaria canker caused by natural and artificial inoculation on the growth and volume loss rate of young poplar trees were studied．The results showed that the num-bers of spots on stem were positively related to the disease index and volume loss rate．The height and breast height diameter of trees were effected by the number of the spots on stem (over 25)．When the spots spread around the stem．the loss rates of breast height diameter and volume became prominent．The cankers mainly occurred on little vesicles (about 0.8 cm in diameter)of young trees stem．As，trees grew older the disease resistence became stronger and the disease incidence and vol-ume loss rate dropped．The control methods should be taken at the developmental stage of young poplar trees，so as to reduce the disease incidence and loss of growth and volume．

Key words: Dothiorella gregaria, Volume loss rate of timber, Populus×beijingensis, Populus×xiaozhuanica cv．popularis’